"Andy Hall" wrote in message
...
On Sat, 4 Sep 2004 10:55:22 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Sat, 4 Sep 2004 09:39:31 +0100, "IMM" wrote:


"Andy Hall" wrote in message


You simply connect the modulating boiler via either a diverter valve
or two (or more) zone valves with one way going to heat the heatbank
and the other to the radiators. The boiler will handle both in
the most efficient way. It is pointless to make it any more
complicated than that.

The boiler will not have load compensation modulation control, so he
is
on
the right track.

Not if it is a simple external box with on/off control of the boiler.
If it is working, the best it can do is to cycle the boiler on and off
during heat demand periods of the room thermostat to reduce or
increase the average heat output.

When he couples it to an "integrated" heat bank matters are very
different.

Yes. Worse if the sole source of heat is the condensing boiler.

You clearly do not understand.

On Sat, 4 Sep 2004 13:14:02 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Sat, 4 Sep 2004 10:51:59 +0100, "IMM" wrote:

It is when appropriate weather compensating
control is used, to ensure the
heat bank, or lower section of heat bank, is
maintained at the variable
setpoint dictated by the compensator.

The heatbank will always introduce a
dampening factor into the control
loop.

Not so. It will prevent/reduce boioer cycling that is for certain.

In the DHW case where either the water in the heatbank is cold or
where the rate of use of heat via the plate heat exchanger massively
exceeds the boiler capacity, boiler cycling will obviously not occur.
That much is obvious.

In the case where the heatbank is sitting between a modulating boiler
and the radiator load, it will screw up the control loop and reduce
the efficiency of the boiler, simply because the boiler is unable to
monitor the radiator load directly.

If you use a non modulating boiler and control it in some way based on
the heatbank temperature, that may be better than a non modulating
boiler relying purely on its internal thermostat. However, since the
burner is either full on or off, it is a) cycling and b) not operating
at the optimum temperature - unless you are talking about a
non-condensing boiler as well, of course.

If you use a modulating boiler and attempt to control it in an on/off
fashion as an external simple weather compensator will try to do, then
the efficiency will be worsened as compared with allowing the boiler
to monitor the radiator water temperature directly.



The element that is intended to be
controlled is the room
temperature, not the water temperature
of the heatbank.

Your comprehension is poor. The boiler/heat bank maintain the lowers section
of the heat bank at the temperature that the rads require for optimum
performance. That is very simple.

It is very simple, and you have it wrong. There is nothing to be
gained with partitioning a heatbank when a gas condensing boiler is
the sole source of energy. Further to that there is nothing to be
gained by having a heatbank in the radiator part of the load at all in
this instance.




The weather compensator, if integrated
with the boiler should move the
operating curve of the boiler up and down
to match the load.

This weather compensator is NOT integrated with a boiler. This you can't
understand.

Oh good grief.

I am fully aware that this weather compensator is not integrated with
the boiler. That is why using this type with this application is
completely pointless.

There are three useful applications for weather compensation:

a) An external, simple one of the type you describe, like the BEM5000,
which has analogue input sensors and a switched output which cycles
the boiler on and off. This is useful wih conventional, especially
older and possibly overpowered boilers where the hysteresis of the
built in thermostat is large and the boiler has a tendency to cause
the room temperature to overshoot; and the thermal characteristics of
the house tend to cause the same. This type of device reduces the
average radiator temperature by switching the boiler on and off rather
than letting its thermostat do the job. It's a crude system and may
make an improvement in this environment.

b) An external temperature sensor connected to a modulating,
condensing boiler's microprocessor. This type of controller already
has analogue inputs from the flow and return temperatures and can
control burn rate and even the pump. This additional sensor gives
additional data from the environment outside the house which will
affect the internal temperature after a time. The boiler can then
adjust accordingly as well as maintaining minimum power level and
temperature.

It isn't possible to achieve the same levels of control and efficiency
using method a) as this.

c) A commercial system, where there is an external energy management
system having multiple analogue sensors inside and out, and able to
monitor the water temperatures. This type of controller is able to
control a boiler or boilers which are able to modulate, but by the use
of some kind of digital signal (PWM or coded), or via an analogue
control voltage or current (e.g. 4-20mA, 0-10v etc.)


Your proposal is for something that is basically a type a)
arrangement, but you are claiming that it is equivalent to or better
than type b) or c). This is patent nonsense.



If you switch to maintaining the temperature
of part of the heatbank to maintain a set point
according to the outside temperature, you
introduce a double control loop.

Nope.

Of course you do. One loop is from boiler to heatbank, the other
from heatbank via radiators to room.


In the piece between the heatbank
and the boiler, if you use the
typical separate box type of weather
compensator, you will have an
analogue sensor for outside

Yes.

and one for inside,

?? One to sense the temp of the heat bank

plus an input for a
switched room thermostat.

Uh! Switched? room temp trimming is analogue unless to have a cheapo.

take a look at the BEM5000. This is the common weather compensator
and is hardly cheap.

It has a switched input for the room thermostat.

Contrast this to the Worcester Bosch Greenstar, which can have a
modulating room thermostat as an option for £42.



The inside analogue sensor would
normally be used on the boiler return,

Or boiler flow, which most operate on. Used on the heat bank here.

Er no. The important temperature for condensing efficiency is the
boiler return temperature.

For other control applications this is also commonplace because it
gives an indication of what the thermal load is doing.

The BEM5000 uses the sensor on the return.


but could be used on the return
from the radiators to the heatbank.

Could be on the cylinder not far from the boiler/rads returns pipes.

That makes it even worse. The temperature of the cylinder wall is
only vaguely related to the return pipes and will have a time lag.


Neither is ideal because
connecting it to the radiator
return means that the controlled device
(boiler) has the damping effect of the
heatbank in between which will
adversely influence the control loop.
Having it on the boiler return
means that the temperature being monitored
relates to heat use by the
heatbank and not the room space.

It is clear you do not understand.

It's clear that I do, and that your scheme gets more an more
complicated and less useful/

The rad circuits are off the bottom of
the heat bank and have their own pump. Easy.

An extra pump.

?The boilers flow and return
is off the heat bank, at the bottom of the heat bank. The compensator has
a probe on the bottom section of the heat bank producing a mass of water at
the temp the rads require. The lower temp at the bottom on part load will
ensure low temp return for high efficient condenser operation, with an
expensive complex boiler.

I presume that you mean without an expensive complex boiler.

Do you think that the Greenstar at £725 is expensive?
If you take off the £300 or so needed to implement your scheme, plus
the poorer long term reliability because of the extra components, you
have about £400 to spend. Are you saying that you can get a good
quality condensing boiler for this.?

Since the external box weather compensator is going to turn the boiler
on and off to maintain the temperature, it will not run at its most
efficient. You would be trying to match a (say) 30kW boiler into a
(say) 10kW load. The boiler cannot run efficiently like that.


You have to know what you are controlling
before you apply control. You
don't.

It is very obvious what is being controlled.
One part is the room temperature.

The room temp influence only trims.

This depends on the thermal characteristics of the building.


The other part is controlling
the boiler firing level
most efficiently to match the room
requirement.

No. Get the boiler to heat a mass of water all at one time, to what
temperature the room requires.

This is why your approach is nonsense.

If you were to connect the modulating boiler directly to the
radiators, an average flow temperature will be in the 50 degree area.

If you try to do this via part of a heatbank and set that temperature,
there is relatively little energy storage - the typical volume of
water is perhaps half of the radiator capacity.

Very soon, the water temperature in the heatbank will have fallen and
the boiler has to come on again. In effect, you are making it cycle
by having regular relatively short full power burns.

This is not as efficient as letting the boiler run continuously at the
temperature required for the radiators.



In the case of a
modulating, condensing boiler,

No need for a modulating condensing boiler./

There are very few quality ones that don't.

Most do modulate, but heating
boilers modulate on flow setpoint temp.

.... and also account for the return temperature.

As the boiler will be on full, when
heating the mass of water for CH very rare will it modulate.

It will be cycling inefficiently instead.

Not only that, the radiator temperatures will be fluctuating as well.

Fundamentally, you can either let the heatbank cool right down and
reheat it at full power which causes the boiler to run less
efficiently and radiator temperatures to vary, or you can attempt to
maintain a setpoint. If you do the latter, then having the boiler
going on and off is not the best way to do it.




In a system where the only source of heat input is a gas condensing
boiler, there is no point in putting a heat bank in the middle because
it simply distorts the control algorithm, and offers no advantages.

You still don't understand.

I think that you don't or are simply being obtuse.




it also screws up the primary purpose
of the heatbank, which is to
provide an energy store to deliver
large amounts of energy quickly to
a heat exchanger.

Primary?

And to prevent boiler cycling and giving on-demand mains pressure hot water.
Eliminating cold water storage tanks.

That is implicit in what I said.


With a heat bank the DHW and CH
circuits don't care about the boiler.

They have totally different characteristics.

The DHW application needs large amounts of heat for relatively short
periods of time. That is why it is called a heat *bank*. It
allows overdrafts relative to the capabilities of the boiler.

The CH application requires much smaller amounts of heat on a
continuous basis with quite slow rates of change of demand.


The boiler can be controlled more
efficiently by having it heat one mass of water very quickly and in one long
efficient burn.

That is only true for the DHW case. For the CH case it is not. We
have already established for a condensing boiler that it will run more
efficiently at lower temperatures and power levels continuously than
by switching on and off.

For the DHW application, the main purpose of a long burn at high power
level is to transfer as much energy as possible back into the cylinder
as fast as possible.




Taken further it can heat two masses of water at different
temperatures.

So now we have two heatbanks?


High for DHW and low for CH. Taken further again, the CH mass
of water can be at variable temperatures to what the outside weather
dictates. When called to heat the CH mass of water it does it in one long
burn no matter what temperature the CH water mass is.

The burn and cycle time will vary with the rate of use of energy and
the amount of temperature drop allowed before reheating is initiated.
This is far from efficient.



A BEM5000 costs £188

A diverter valve costs £56

You forgot the extra pump to run the radiator circuit - £56 for a
Grundfos

All prices from Discounted Heating. Total cost is £311.

You can buy a Worcester Greenstar 28HE for £725 from them.

What 28kW condensing boiler you going to buy from Discounted Heating
for £410 that is any good?

But you save a wedge on a 1.5K load compensating boiler and musch simpler.

Where did you get £1.5k from?

I mentioned the WB Greenstar at £725 with all these features.



When combined with heat banks and heating a large mass of water matters
are
very different. This you can't understand. This is very sad.

Of course they are very different
and I understand the difference
perfectly.

Not so.

Sigh.....


The results, if using a condensing boiler as the sole
source of energy, will be inferior, by definition, than the direct
connection of the boiler to the radiators as the manufacturers intend
and design.

You clearly do not understand. "by definition, than the direct connection of
the boiler to the radiators as the manufacturers intend and design.". I am
not on about one of theses type of boiler.

So you mean a non modulating boiler? These are not as efficient as
modulating types by definition, and all that you are proposing is to
put a simple switching controller and a damping element in front in an
attempt to make them so. This is a nonsense.



The value in a heatbank is in its
ability to store energy at high
temperature to run a plate heat
exchanger for the hot water.

It is?

It is also useful in the introduction of
heat from other sources such as
solar.

..and a condensing boiler.


Not if that is the only source.




Even with all the extra controls that you describe,
the efficiency will be worsened.

You clearly do not understand.

I clearly do.


To suggest that coupling a
switching controller with a simple
boiler is an improvement is
laughable.

You clearly do not understand.

ditto. etc.



..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...

Not so. It will prevent/reduce boiler cycling that is for certain.

In the case where the heatbank is sitting
between a modulating boiler
and the radiator load, it will screw up
the control loop and reduce
the efficiency of the boiler, simply
because the boiler is unable to
monitor the radiator load directly.

Nonsense. Thew boiler doesn't need to know the return temp of the rads.

If you use a non modulating boiler
and control it in some way based on
the heatbank temperature, that may
be better than a non modulating
boiler relying purely on its internal
thermostat.

You are getting there.

However, since the
burner is either full on or off,
it is a) cycling

Failed.

and b) not operating
at the optimum temperature

Failed again.

- unless you are talking about a
non-condensing boiler as well, of course.

If you use a modulating boiler
and attempt to control it in an on/off
fashion as an external simple weather
compensator will try to do, then
the efficiency will be worsened as
compared with allowing the boiler
to monitor the radiator water temperature
directly.

Failed again. When on it heats a large mass of water. This confuses you.
That is sad.

The element that is intended to be
controlled is the room
temperature, not the water temperature
of the heatbank.

Your comprehension is poor. The boiler/heat bank
maintain the lowers section
of the heat bank at the temperature that
the rads require for optimum
performance. That is very simple.

It is very simple, and you have it wrong.

Failed again. It is right it is just above.

There is nothing to be
gained with partitioning a heatbank
when a gas condensing boiler is
the sole source of energy.

Lots to be gained. A cheaper simpler boiler and vastly reduced/elimination
of cycling.

Further to that there is nothing to be
gained by having a heatbank in the
radiator part of the load at all in
this instance.

A heat bank a neutral point. A great advantage. The boiler and rads operate
independently of each other. Constant flow can be through the boiler at all
times. No silly pressure diif valves needed. Rads with TRVs can be
virtually off and the boiler doesn't know or care.

The weather compensator, if integrated
with the boiler should move the
operating curve of the boiler up and down
to match the load.

This weather compensator is NOT
integrated with a boiler. This you can't
understand.

Oh good grief.

Sounds encouraging.

I am fully aware that this weather compensator is not integrated with
the boiler. That is why using this type with this application is
completely pointless.

Failed again.

There are three useful applications for weather compensation:

a) An external, simple one of the type you describe, like the BEM5000,
which has analogue input sensors and a switched output which cycles
the boiler on and off. This is useful wih conventional, especially
older and possibly overpowered boilers where the hysteresis of the
built in thermostat is large and the boiler has a tendency to cause
the room temperature to overshoot; and the thermal characteristics of
the house tend to cause the same. This type of device reduces the
average radiator temperature by switching the boiler on and off rather
than letting its thermostat do the job. It's a crude system and may
make an improvement in this environment.

b) An external temperature sensor connected to a modulating,
condensing boiler's microprocessor. This type of controller already
has analogue inputs from the flow and return temperatures and can
control burn rate and even the pump. This additional sensor gives
additional data from the environment outside the house which will
affect the internal temperature after a time. The boiler can then
adjust accordingly as well as maintaining minimum power level and
temperature.

It isn't possible to achieve the same levels of control and efficiency
using method a) as this.

It is. When using heat bank.

c) A commercial system, where there is an external energy management
system having multiple analogue sensors inside and out, and able to
monitor the water temperatures. This type of controller is able to
control a boiler or boilers which are able to modulate, but by the use
of some kind of digital signal (PWM or coded), or via an analogue
control voltage or current (e.g. 4-20mA, 0-10v etc.)


Your proposal is for something that is basically a type a)
arrangement, but you are claiming that it is equivalent to or better
than type b) or c). This is patent nonsense.

None of your points has a heat bank incorporated, so squewed.

If you switch to maintaining the temperature
of part of the heatbank to maintain a set point
according to the outside temperature, you
introduce a double control loop.

Nope.

Of course you do. One loop is from boiler to heatbank, the other
from heatbank via radiators to room.

Only one loop. Boiler to heat bank, dictated to by outsoide waether
conditions.

In the piece between the heatbank
and the boiler, if you use the
typical separate box type of weather
compensator, you will have an
analogue sensor for outside

Yes.

and one for inside,

?? One to sense the temp of the heat bank

plus an input for a
switched room thermostat.

Uh! Switched? room temp trimming is analogue unless to have a cheapo.

take a look at the BEM5000. This is the common weather compensator
and is hardly cheap.

It is not the only model. It saves the cost of a 1.5K boiler.

It has a switched input for the room thermostat.

Not good if room influence is incorporated.

Contrast this to the Worcester Bosch Greenstar, which can have a
modulating room thermostat as an option for £42.

Only doe one zone. A heat bank can have two zones fed from it. Each zone
hits a neutral point. Microbore can be used when both go back to one
neutral point.

The inside analogue sensor would
normally be used on the boiler return,

Or boiler flow, which most operate on.
Used on the heat bank here.

Er no.

Er yes, depending on application.

The important temperature for condensing efficiency is the
boiler return temperature

Lower the flow and the return follows suit.

For other control applications this
is also commonplace because it
gives an indication of what the thermal
load is doing.

Using a heat bank the thermal load is irrelevant. The boiler doesn't care
about it.

The BEM5000 uses the sensor on the return.

Just an option they use.

but could be used on the return
from the radiators to the heatbank.

Could be on the cylinder not far from
the boiler/rads returns pipes.

That makes it even worse.

failed. makes it better as it sense the mass of water, which is at the temp
the building requires.

The temperature of the cylinder wall is
only vaguely related to the return pipes
and will have a time lag.

The boiler doesn't want to know the rads return temperature. I doesn't
care.

Neither is ideal because
connecting it to the radiator
return means that the controlled device
(boiler) has the damping effect of the
heatbank in between which will
adversely influence the control loop.
Having it on the boiler return
means that the temperature being monitored
relates to heat use by the
heatbank and not the room space.

It is clear you do not understand.

It's clear that I do,

No. It is clear you do not understand.

and that your scheme gets more an more
complicated and less useful/

It is simple. It also works very well indeed.

The rad circuits are off the bottom of
the heat bank and have their own pump. Easy.

An extra pump.

That will break the bank.

The boilers flow and return
is off the heat bank, at the bottom of the heat bank. The compensator
has
a probe on the bottom section of the heat bank producing a mass of water
at
the temp the rads require. The lower temp at the bottom on part load
will
ensure low temp return for high efficient condenser operation, with an
expensive complex boiler.

I presume that you mean without an expensive complex boiler.

yep.

Do you think that the Greenstar at £725 is expensive?

Not bad for what it is. Others are cheaper. This is besides the point.

If you take off the £300 or so needed
to implement your scheme, plus
the poorer long term reliability because
of the extra components,

You have a simpler boiler with less components.

Since the external box weather
compensator is going to turn the boiler
on and off to maintain the temperature,
it will not run at its most efficient.

failed again.

You would be trying to match a (say) 30kW boiler into a
(say) 10kW load. The boiler cannot run efficiently like that.

You fail to understand. A mass of water is heated to a temp a compensator
dictates. The mass of water is heated and the rads take off as much heat as
they need. Wheh the mass of water needs heating the 30kW boiler reheats the
mass. The boiler know or care about loads of rad circuit.

You have to know what you are controlling
before you apply control. You
don't.

It is very obvious what is being controlled.
One part is the room temperature.

The room temp influence only trims.

This depends on the thermal characteristics of the building.

It doesn't, it depends on what compensator you use.

The other part is controlling
the boiler firing level
most efficiently to match the room
requirement.

No. Get the boiler to heat a mass of
water all at one time, to what
temperature the room requires.

This is why your approach is nonsense.

failed again. See above

If you were to connect the
modulating boiler directly to the
radiators, an average flow temperature
will be in the 50 degree area.

Once the buildings heat demand is below the minimum of the boiler cycling
starts.

If you try to do this via part of a
heatbank and set that temperature,
there is relatively little energy storage -
the typical volume of
water is perhaps half of the radiator capacity.

You make sure the storage is at least x 2 of rads.

Very soon, the water temperature in
the heatbank will have fallen and
the boiler has to come on again.

Getting it.

In effect, you are making it cycle
by having regular relatively short full power burns.

No. short power burns at lomng intervals.

This is not as efficient as
letting the boiler run continuously at the
temperature required for the radiators.

failed again.

In the case of a
modulating, condensing boiler,

No need for a modulating condensing boiler.

There are very few quality ones that don't.

Most do modulate, but heating
boilers modulate on flow setpoint temp.

... and also account for the return temperature.

As the boiler will be on full, when
heating the mass of water for CH
very rare will it modulate.

It will be cycling inefficiently instead.

failed again. Not so.

Not only that, the radiator temperatures
will be fluctuating as well.

Fluctuation of rad temps would be minimum.

Fundamentally, you can either
let the heatbank cool right down and
reheat it at full power which causes
the boiler to run less efficiently

failed again. the boiler runs efficiently. as the mass of water is to the
temp the building requires.

and radiator temperatures to vary,
or you can attempt to maintain a
setpoint. If you do the latter, then having the boiler
going on and off is not the best way to do it.

failed again.

In a system where the only source of heat input is a gas condensing
boiler, there is no point in putting a heat bank in the middle because
it simply distorts the control algorithm, and offers no advantages.

You still don't understand.

I think that you don't or are simply being obtuse.

No. You still don't understand.

it also screws up the primary purpose
of the heatbank, which is to
provide an energy store to deliver
large amounts of energy quickly to
a heat exchanger.

Primary?

And to prevent boiler cycling and giving on-demand mains pressure hot
water.
Eliminating cold water storage tanks.

That is implicit in what I said.

With a heat bank the DHW and CH
circuits don't care about the boiler.

They have totally different characteristics.

Which is a great advantage. Divide and rule.

The DHW application needs
large amounts of heat for relatively short
periods of time. That is why it is
called a heat *bank*.

failed again. It is called a heat bank because it is a bank of heat.

It allows overdrafts relative to the
capabilities of the boiler.

The CH application requires much
smaller amounts of heat on a
continuous basis with quite slow rates of change of demand.

The boiler can be controlled more
efficiently by having it heat one mass of water very quickly and in one
long
efficient burn.

That is only true for the DHW case.

failed again. applicable to CH.

For the CH case it is not.

failed again. applicable to CH.

We have already established for
a condensing boiler that it will run more
efficiently at lower temperatures

Good. getting better.

and power levels continuously than
by switching on and off.

Faile again. Continuous power levels when burning in one long efficient
burn.

For the DHW application, the main
purpose of a long burn at high power
level is to transfer as much energy as
possible back into the cylinder
as fast as possible.

Good.

Taken further it can heat two masses
of water at different
temperatures.

So now we have two heatbanks?

One split into two separte temperature zones.

High for DHW and low for CH.
Taken further again, the CH mass
of water can be at variable temperatures
to what the outside weather
dictates. When called to heat the CH
mass of water it does it in one long
burn no matter what temperature
the CH water mass is.

The burn and cycle time will vary
with the rate of use of energy and
the amount of temperature drop
allowed before reheating is initiated.
This is far from efficient.

Efficient for the boiler usage.

A BEM5000 costs £188

A diverter valve costs £56

You forgot the extra pump to run the radiator circuit - £56 for a
Grundfos

All prices from Discounted Heating. Total cost is £311.

You can buy a Worcester Greenstar 28HE for £725 from them.

What 28kW condensing boiler you going to buy from Discounted Heating
for £410 that is any good?

But you save a wedge on a 1.5K load compensating boiler and much simpler.

Where did you get £1.5k from?

A load compensating modulation, outside waether compensating boioer is about
1K

Using a heat bank load compensating modulation is not required.

I mentioned the WB Greenstar at £725 with all these features.

Outside weather compensation?

When combined with heat banks and heating a large mass of water
matters
are
very different. This you can't understand. This is very sad.

Of course they are very different
and I understand the difference
perfectly.

Not so.

Sigh.....


The results, if using a condensing boiler as the sole
source of energy, will be inferior, by definition, than the direct
connection of the boiler to the radiators as the manufacturers intend
and design.

You clearly do not understand. "by definition, than the direct connection
of
the boiler to the radiators as the manufacturers intend and design.". I
am
not on about one of theses type of boiler.

So you mean a non modulating boiler?

Yes.

These are not as efficient as
modulating types by definition,

failed again. They are. It depends on how it is controlled and what
conditions it is run in.

and all that you are proposing is to
put a simple switching controller and
a damping element in front in an
attempt to make them so. This is a nonsense.

2/10 total failure. And you say O and A levels are getting easier. You
just failed.

The value in a heatbank is in its
ability to store energy at high
temperature to run a plate heat
exchanger for the hot water.

It is?

It is also useful in the introduction of
heat from other sources such as
solar.

..and a condensing boiler.

Not if that is the only source.

Even with all the extra controls that you describe,
the efficiency will be worsened.

You clearly do not understand.

I clearly do.

failed again.

To suggest that coupling a
switching controller with a simple
boiler is an improvement is
laughable.

You clearly do not understand.

ditto. etc.

2/10. very poor mark. You should feel ashamed of yourself.

On Sat, 4 Sep 2004 17:22:51 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .

Not so. It will prevent/reduce boiler cycling that is for certain.

In the case where the heatbank is sitting
between a modulating boiler
and the radiator load, it will screw up
the control loop and reduce
the efficiency of the boiler, simply
because the boiler is unable to
monitor the radiator load directly.

Nonsense. Thew boiler doesn't need to know the return temp of the rads.


It does if it is going to be involved in an efficient control system
where the heat output to the radiators and the heating space are
measured and controlled without lag, then it most certainly does.


If you use a non modulating boiler
and control it in some way based on
the heatbank temperature, that may
be better than a non modulating
boiler relying purely on its internal
thermostat.

You are getting there.

I said *may*, and it will only be in so far as a difference between an
analogue sensor on the cylinder and a thermostat with substantial
hysteresis on the boiler.

The whole thing is then wrecked by the external controller driving the
boiler in on/off mode.


However, since the
burner is either full on or off,
it is a) cycling

Failed.

So are you saying that the external controller doesn't control the
boiler by turning it on and off. You'll be telling me that it
operates a motor on the gas tap next.



and b) not operating
at the optimum temperature

Failed again.

If it is a condensing boiler, on/off control with full output or
nothing will not operate it efficiently.


- unless you are talking about a
non-condensing boiler as well, of course.

If you use a modulating boiler
and attempt to control it in an on/off
fashion as an external simple weather
compensator will try to do, then
the efficiency will be worsened as
compared with allowing the boiler
to monitor the radiator water temperature
directly.

Failed again. When on it heats a large mass of water. This confuses you.
That is sad.

The trouble is that it doesn't.


On the one hand you are saying that you are going to have part of a
heatbank operating at a set point and being maintained that way by
controlling the heat going in. By definition, if you do that with a
non-modulating boiler with power output level larger, probably
substantially larger than the rate of use by the radiators, then you
will have to cycle the boiler. That is unless you know some law of
physics whereby heat can be stored in a different dimension.

On the other hand, you say that you want to have long burns on the
boiler to improve efficiency (which it only does by not having
cycling, not because of running temperatures). If you do that, you
are going to have to let the heatbank (or part thereof in use)
discharge all of its heat before running the boiler again.
This will result in cooling and heating of the radiators, a
fluctuation in heat output and a variation in room temperature.

You can't have it both ways.





The element that is intended to be
controlled is the room
temperature, not the water temperature
of the heatbank.

Your comprehension is poor. The boiler/heat bank
maintain the lowers section
of the heat bank at the temperature that
the rads require for optimum
performance. That is very simple.

It is very simple, and you have it wrong.

Failed again. It is right it is just above.

As I said, you can't have it both ways.




There is nothing to be
gained with partitioning a heatbank
when a gas condensing boiler is
the sole source of energy.

Lots to be gained. A cheaper simpler boiler and vastly reduced/elimination
of cycling.

There's nothing to be gained.

You have added a bunch of complexity and achieved poorer efficiency.

You haven't saved any money either Please provide a make and model
number of one of these "simpler boilers" at around £400 Discounted
Heating prices, that is anywhere near the quality of a WB Greenstar.




Further to that there is nothing to be
gained by having a heatbank in the
radiator part of the load at all in
this instance.

A heat bank a neutral point. A great advantage.

Only in circumstances where

a) multiple heat sources are being combined or

b) when there is a need to store heat because of the requirement of
large amounts to heat water, or

c) when the boiler, because of its sizing and limited or no control
range would naturally cycle.

This is not any of those cases.


The boiler and rads operate
independently of each other. Constant flow can be through the boiler at all
times.

That's clearly nonsense. The only way that they can operate truly
independently is by having two heat banks. Are you advocating that
now?

The heat requirement into the cylinder will be quite different for DHW
vs. CH. In the former case, it will be maximum transfer after water
has been run. In the latter, either the heat will have to be fed in
at the rate of use (less than the boiler maximum output) or at full
power for short periods.

Where you have got the idea of constant flow from, goodness only
knows. If you mean constant water flow, regardless of demand, it is
going to be wasteful when neither CH nor DHW are demanding heat.


No silly pressure diif valves needed. Rads with TRVs can be
virtually off and the boiler doesn't know or care.

There aren't anyway. If the pump is integral to the boiler, the
boiler's controller can match it to the heat load. An exterior one
can sense the flow and pressure conditions and also reduce output.





The weather compensator, if integrated
with the boiler should move the
operating curve of the boiler up and down
to match the load.

This weather compensator is NOT
integrated with a boiler. This you can't
understand.

Oh good grief.

Sounds encouraging.

I am fully aware that this weather compensator is not integrated with
the boiler. That is why using this type with this application is
completely pointless.

Failed again.

I'm not repeating the obvious, and I'm certainly not about to educate
you about control systems.



There are three useful applications for weather compensation:

a) An external, simple one of the type you describe, like the BEM5000,
which has analogue input sensors and a switched output which cycles
the boiler on and off. This is useful wih conventional, especially
older and possibly overpowered boilers where the hysteresis of the
built in thermostat is large and the boiler has a tendency to cause
the room temperature to overshoot; and the thermal characteristics of
the house tend to cause the same. This type of device reduces the
average radiator temperature by switching the boiler on and off rather
than letting its thermostat do the job. It's a crude system and may
make an improvement in this environment.

b) An external temperature sensor connected to a modulating,
condensing boiler's microprocessor. This type of controller already
has analogue inputs from the flow and return temperatures and can
control burn rate and even the pump. This additional sensor gives
additional data from the environment outside the house which will
affect the internal temperature after a time. The boiler can then
adjust accordingly as well as maintaining minimum power level and
temperature.

It isn't possible to achieve the same levels of control and efficiency
using method a) as this.

It is. When using heat bank.

Not if the controller is operating the boiler by turning it on and
off, which it will have to do in the case of a non modulating one.
This is how the BEM5000 works.
All that the heatbank is doing is to add a lag in the control path.



c) A commercial system, where there is an external energy management
system having multiple analogue sensors inside and out, and able to
monitor the water temperatures. This type of controller is able to
control a boiler or boilers which are able to modulate, but by the use
of some kind of digital signal (PWM or coded), or via an analogue
control voltage or current (e.g. 4-20mA, 0-10v etc.)


Your proposal is for something that is basically a type a)
arrangement, but you are claiming that it is equivalent to or better
than type b) or c). This is patent nonsense.

None of your points has a heat bank incorporated, so squewed.

Again. All that the heatbank does is to introduce a lag in the
control system. You can either choose to keep it topped up with heat
on a tight setpoint window, in which case the boiler will have to be
cycled a lot, or you can let the heatbank temperature drop by the use
of a wide window in which case it will cycle less and the radiator
temperatures will drop.



If you switch to maintaining the temperature
of part of the heatbank to maintain a set point
according to the outside temperature, you
introduce a double control loop.

Nope.

Of course you do. One loop is from boiler to heatbank, the other
from heatbank via radiators to room.

Only one loop. Boiler to heat bank, dictated to by outsoide waether
conditions.

There is also the room thermostat or TRVs as an outer loop.


The heatbank is not representative of the characteristics of the
radiator heat load. All that you achieve at best is a rather poor
attempt at providing a heat source to the radiators, the temperature
of which is varied according to outside conditions. THe boiler energy
manager, will attempt to maintain the heatbank temperature by cycling
the boiler on and off.

There is no value in doing that in comparison with a true modulation
of the boiler.

In the piece between the heatbank
and the boiler, if you use the
typical separate box type of weather
compensator, you will have an
analogue sensor for outside

Yes.

and one for inside,

?? One to sense the temp of the heat bank

plus an input for a
switched room thermostat.

Uh! Switched? room temp trimming is analogue unless to have a cheapo.

take a look at the BEM5000. This is the common weather compensator
and is hardly cheap.

It is not the only model. It saves the cost of a 1.5K boiler.

Please provide an example of a suitable weather compensating
controller at the same or lower price than the BEM5000.

Please also explain how you believe that on/off controlling a simple
boiler is more efficient than a modulating, condensing one.

Please explain where the figure of £1.5k comes into this.
The discussion is around something like a WB Greenstar with price
point of £725. It's not good trying to justify your argument by
adding in £800 of cost which is irrelevant.

THe arithmetic is between a good quality modulating boiler at £725 vs.
the cost of some alleged "simple" boiler at £400 plus your controls at
£300.



It has a switched input for the room thermostat.

Not good if room influence is incorporated.

Exactly.


Contrast this to the Worcester Bosch Greenstar, which can have a
modulating room thermostat as an option for £42.

Only doe one zone. A heat bank can have two zones fed from it. Each zone
hits a neutral point.

This is irrelevant. The issue is still one of energy in vs. energy
out.

Microbore can be used when both go back to one
neutral point.

This is irrelevant as well. Microbore is simply a size of tube.
There is nothing magic about it.


The inside analogue sensor would
normally be used on the boiler return,

Or boiler flow, which most operate on.
Used on the heat bank here.

Er no.

Er yes, depending on application.

Sigh.....


The important temperature for condensing efficiency is the
boiler return temperature

Lower the flow and the return follows suit.

Well obviously. Most modulating boilers that I have seen have both
flow and return sensors.



For other control applications this
is also commonplace because it
gives an indication of what the thermal
load is doing.

Using a heat bank the thermal load is irrelevant. The boiler doesn't care
about it.

Oh dear. Of course it's relevant.

THe DHW load is an overdraft on the heatbank of anything up to 200kW
for short periods of time. Boiler requirement to recharge is full
power, for a short time.

The CH load is likely to be 20-80% of full load according to demand
and is continuous during short to medium time periods.




The BEM5000 uses the sensor on the return.

Just an option they use.

It's pretty critical to the operation of the operation of the unit.

From the instructions:

"The ESMA must be mounted on a pipe connected to the boiler return
tapping, between the bypass and the boiler, using the clamping band
provided, in a position where it will sense the temperature of the
water returning from the HEATING circuit"

ESMA is the return sensor. It doesn't say *may* but *must*.

Regarding the room thermostat it uses the words

"If a room thermostat is used....."

i.e. optional.



but could be used on the return
from the radiators to the heatbank.

Could be on the cylinder not far from
the boiler/rads returns pipes.

That makes it even worse.

failed. makes it better as it sense the mass of water, which is at the temp
the building requires.

The mass of water will be at some temperature. The controller should
be trying to measure the radiator return temperature in your example
because that represents something derived from the heat load into the
space. The temperature of the heatbank is not well related to that.


The temperature of the cylinder wall is
only vaguely related to the return pipes
and will have a time lag.

The boiler doesn't want to know the rads return temperature. I doesn't
care.

In the case of your external controller and full power switched boiler
set up, obviously not. The closest would be that the controller
wants to know the return temperature from the radiators.

However the exercise is pointless because it will be worse than
letting a controller in the boiler do the job.



Neither is ideal because
connecting it to the radiator
return means that the controlled device
(boiler) has the damping effect of the
heatbank in between which will
adversely influence the control loop.
Having it on the boiler return
means that the temperature being monitored
relates to heat use by the
heatbank and not the room space.

It is clear you do not understand.

It's clear that I do,

No. It is clear you do not understand.

It's behind you.......


and that your scheme gets more an more
complicated and less useful/

It is simple. It also works very well indeed.

Have you implemented and measured this in comparison to a modulating
condensing boiler connected to radiators directly?

If so, which boiler and controller did you use for each?



The rad circuits are off the bottom of
the heat bank and have their own pump. Easy.

An extra pump.

That will break the bank.

None of this breaks the bank.

The point is that you are proposing an unnecessarily complicated
system, which patently can't perform as well as one with analogue
sensing of water temperatures and modulation of the burner.

You are unable to provide types and prices of components for this that
will come in at under the price point for a modulating system.



The boilers flow and return
is off the heat bank, at the bottom of the heat bank. The compensator
has
a probe on the bottom section of the heat bank producing a mass of water
at
the temp the rads require. The lower temp at the bottom on part load
will
ensure low temp return for high efficient condenser operation, with an
expensive complex boiler.

I presume that you mean without an expensive complex boiler.

yep.

Do you think that the Greenstar at £725 is expensive?

Not bad for what it is. Others are cheaper. This is besides the point.

Not really. You can get modulating, condensing boilers for a bit
less than this, or a bit more.

What is the make and model number of your alleged "simple" boiler,
with equivalent build quality to this?



If you take off the £300 or so needed
to implement your scheme, plus
the poorer long term reliability because
of the extra components,

You have a simpler boiler with less components.

They are all external in various boxes, valves and extra pumps.



Since the external box weather
compensator is going to turn the boiler
on and off to maintain the temperature,
it will not run at its most efficient.

failed again.

You would be trying to match a (say) 30kW boiler into a
(say) 10kW load. The boiler cannot run efficiently like that.

You fail to understand. A mass of water is heated to a temp a compensator
dictates. The mass of water is heated and the rads take off as much heat as
they need. Wheh the mass of water needs heating the 30kW boiler reheats the
mass. The boiler know or care about loads of rad circuit.

No you fail to understand.

The equations are simple.

In the modulating, condensing boiler case, if the load to the
radiators needs to be 10kW, the boiler will drop down to that output
level and a low running temperature, continuously. There will be no
cycling at all and the boiler will be running well into into the
higher efficiency part of its operating curve.

In your simple boiler case, the 10kW load match will have to be
achieved (assuming a 30kW boiler) by running it at full power for a
third of the time. This is less efficient, a) because the boiler
is going on and off and b) because it is not operating on the most
efficient part of the curve.
You can make those on/off periods shorter or longer by how large you
make the allowable temperature drop in the heatbank, but it will
average to a 3:1 off/on.



You have to know what you are controlling
before you apply control. You
don't.

It is very obvious what is being controlled.
One part is the room temperature.

The room temp influence only trims.

This depends on the thermal characteristics of the building.

It doesn't, it depends on what compensator you use.

Oh really. What kind of compensator do you have in mind?

It is possible to run a modulating boiler purely based on outside
temperature measurement, but the effect will be that the inside
temperature will tend to fluctuate.



The other part is controlling
the boiler firing level
most efficiently to match the room
requirement.

No. Get the boiler to heat a mass of
water all at one time, to what
temperature the room requires.

This is why your approach is nonsense.

failed again. See above

Sigh.


If you were to connect the
modulating boiler directly to the
radiators, an average flow temperature
will be in the 50 degree area.

Once the buildings heat demand is below the minimum of the boiler cycling
starts.

Obviously. However it is far better if it cycles between 0 and 20%
of full load than 0 and 100%


If you try to do this via part of a
heatbank and set that temperature,
there is relatively little energy storage -
the typical volume of
water is perhaps half of the radiator capacity.

You make sure the storage is at least x 2 of rads.

So let's see. My radiators and pipework have a capacity of about
100 litres.

So now you are saying that I need a 200 litre heatbank for this; and
the one for the hot water in addition to that?

Plus I get worse performance and efficiency than a boiler connected
directly to them?

Why would I want to do that?




Very soon, the water temperature in
the heatbank will have fallen and
the boiler has to come on again.

Getting it.

In effect, you are making it cycle
by having regular relatively short full power burns.

No. short power burns at lomng intervals.

The energy still has to be put in.

With a 200 litre cylinder that will be about 30 mins on - I wouldn't
call that short.

It is also not a practically good example because the heatbank has
been run to zero in the intervening time.


This is not as efficient as
letting the boiler run continuously at the
temperature required for the radiators.

failed again.

Do you have figures which demonstrate that running a condensing boiler
at full power with cycling is more efficient than running it on part
power continuously?

If your case were more efficient, why do you imagine that the
manufacturers of modulating boilers arrange them to drop the power and
temperature as the load reduces? Do you imagine that British Gas
sponsors them to use more energy??



In the case of a
modulating, condensing boiler,

No need for a modulating condensing boiler.

There are very few quality ones that don't.

Most do modulate, but heating
boilers modulate on flow setpoint temp.

... and also account for the return temperature.

As the boiler will be on full, when
heating the mass of water for CH
very rare will it modulate.

It will be cycling inefficiently instead.

failed again. Not so.

Not only that, the radiator temperatures
will be fluctuating as well.

Fluctuation of rad temps would be minimum.

Not if you run the temperature in the heatbank down.

What do you believe that the operating window of the heatbank should
be and why?


Fundamentally, you can either
let the heatbank cool right down and
reheat it at full power which causes
the boiler to run less efficiently

failed again. the boiler runs efficiently. as the mass of water is to the
temp the building requires.

So are you saying that you want to maintain the heatbank at close to
the setpoint temperature or allow it to fall?

If so, by how much?




it also screws up the primary purpose
of the heatbank, which is to
provide an energy store to deliver
large amounts of energy quickly to
a heat exchanger.

Primary?

And to prevent boiler cycling and giving on-demand mains pressure hot
water.
Eliminating cold water storage tanks.

That is implicit in what I said.

With a heat bank the DHW and CH
circuits don't care about the boiler.

They have totally different characteristics.

Which is a great advantage. Divide and rule.

That's your best argument so far. It's a pity that it bears no
relationship whatever to the subject matter.




The DHW application needs
large amounts of heat for relatively short
periods of time. That is why it is
called a heat *bank*.

failed again. It is called a heat bank because it is a bank of heat.

That's helpful :-)



It allows overdrafts relative to the
capabilities of the boiler.

The CH application requires much
smaller amounts of heat on a
continuous basis with quite slow rates of change of demand.

The boiler can be controlled more
efficiently by having it heat one mass of water very quickly and in one
long
efficient burn.

That is only true for the DHW case.

failed again. applicable to CH.

This depends on the temperature range that you are going to use.

Are you going to try to maintain the set point or allow the
temperature to fall?



We have already established for
a condensing boiler that it will run more
efficiently at lower temperatures

Good. getting better.

and power levels continuously than
by switching on and off.

Faile again. Continuous power levels when burning in one long efficient
burn.

It will be more efficient at lower temperatures and power levels.
With your proposed simple boiler, this doesn't happen.



For the DHW application, the main
purpose of a long burn at high power
level is to transfer as much energy as
possible back into the cylinder
as fast as possible.

Good.

Taken further it can heat two masses
of water at different
temperatures.

So now we have two heatbanks?

One split into two separte temperature zones.

With what? Some kind of divider or just relying on stratification?

If it's the latter, you are going to get a big interaction between the
performance requirement of the hot water vs. your desired control for
the CH part. Since the characteristics are completely different, you
will end up with a poor compromise.


High for DHW and low for CH.
Taken further again, the CH mass
of water can be at variable temperatures
to what the outside weather
dictates. When called to heat the CH
mass of water it does it in one long
burn no matter what temperature
the CH water mass is.

The burn and cycle time will vary
with the rate of use of energy and
the amount of temperature drop
allowed before reheating is initiated.
This is far from efficient.

Efficient for the boiler usage.

Whatever that means, which is not a lot.



A BEM5000 costs £188

A diverter valve costs £56

You forgot the extra pump to run the radiator circuit - £56 for a
Grundfos

All prices from Discounted Heating. Total cost is £311.

You can buy a Worcester Greenstar 28HE for £725 from them.

What 28kW condensing boiler you going to buy from Discounted Heating
for £410 that is any good?

But you save a wedge on a 1.5K load compensating boiler and much simpler.

Where did you get £1.5k from?

A load compensating modulation, outside waether compensating boioer is about
1K

You introduced the idea of weather compensation as a means to control
the heatbank temperature, just so that you could hook up the radiators
to it - a completely pointless exercise.


Using a heat bank load compensating modulation is not required.

You can equally argue that with a modulating boiler with a room
temperature analogue sensor that outside weather compensation isn't
required.




So you mean a non modulating boiler?

Yes.

These are not as efficient as
modulating types by definition,

failed again. They are. It depends on how it is controlled and what
conditions it is run in.

Certainly with your suggested method of on off control it is not going
to run at anything like the efficiency of a modulating model using its
own temperature sensing.


..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Sat, 4 Sep 2004 17:22:51 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .

Not so. It will prevent/reduce boiler cycling that is for certain.

In the case where the heatbank is sitting
between a modulating boiler
and the radiator load, it will screw up
the control loop and reduce
the efficiency of the boiler, simply
because the boiler is unable to
monitor the radiator load directly.

Nonsense. Thew boiler doesn't
need to know the return temp of the rads.

It does if it is going to be involved
in an efficient control system
where the heat output to the radiators
and the heating space are
measured

They are measured by the weather compensator, with any room temp influence
to drop the slope if need be.

and controlled without lag,
then it most certainly does.

No lag. A mass of water the temperature required is available.

If you use a non modulating boiler
and control it in some way based on
the heatbank temperature, that may
be better than a non modulating
boiler relying purely on its internal
thermostat.

You are getting there.

I said *may*, and it will only be in so
far as a difference between an
analogue sensor on the cylinder
and a thermostat with substantial
hysteresis on the boiler.

Thermostat on the boiler is on full, and will rarely cut out on this.

The whole thing is then wrecked by
the external controller driving the
boiler in on/off mode.

However, since the
burner is either full on or off,
it is a) cycling

Failed.

So are you saying that the external
controller doesn't control the
boiler by turning it on and off.

No.

You'll be telling me that it
operates a motor on the gas tap next.

Nope I will not.

and b) not operating
at the optimum temperature

Failed again.

If it is a condensing boiler, on/off control with full output or
nothing will not operate it efficiently.

You fail to understand condensing boilers, or boilers at all. A boiler will
only raise water a certain temperature with a given flowrate through the
heat exchanger. The flow through it can be constant, as no TRVs used. If
say at x flowrate it raises the water 25C, if the return is 30C only 55C
come out of the flow. Way below the boiler stat set to 82C. When the mass
of water is heated the boiler stat would have never have cut in to cycle the
boiler, so one long efficient burn.

- unless you are talking about a
non-condensing boiler as well, of course.

If you use a modulating boiler
and attempt to control it in an on/off
fashion as an external simple weather
compensator will try to do, then
the efficiency will be worsened as
compared with allowing the boiler
to monitor the radiator water temperature
directly.

Failed again. When on it heats a large
mass of water. This confuses you.
That is sad.

The trouble is that it doesn't.

You are rarther silly now.

On the one hand you are saying that you are going to have part of a
heatbank operating at a set point and being maintained that way by
controlling the heat going in. By definition, if you do that with a
non-modulating boiler with power output level larger, probably
substantially larger than the rate of use by the radiators, then you
will have to cycle the boiler.

The boiler does not cycle when re-heating the mass. Operation: heats the
mass of water mass cools - mass is reheated all at once with "no" boiler
cycling - heat extracted from the water mass by the rad circuit - mass is
reheated all at once with "no" boiler cycling .

That is unless you know some law of
physics whereby heat can be stored
in a different dimension.

You are mad.

On the other hand, you say that you want to have long burns on the
boiler to improve efficiency (which it only does by not having
cycling,


Mor failure. You have droped from 2/10 to 1/10.

not because of running temperatures). If you do that, you
are going to have to let the heatbank (or part thereof in use)
discharge all of its heat before running the boiler again.
This will result in cooling and heating of the radiators, a
fluctuation in heat output and a variation in room temperature.

Any fluctuation would be minimal. the mass of water takes time to cool. It
is not like hot water running though a rad circuit return pipe. very little
mass and less mass in the whole rad circuit than in the stored water mass by
at "least" half as much. The water mass stabilises operation. think hard
about that. Ermmm well don't bother.

You can't have it both ways.

The element that is intended to be
controlled is the room
temperature, not the water temperature
of the heatbank.

Your comprehension is poor. The boiler/heat bank
maintain the lowers section
of the heat bank at the temperature that
the rads require for optimum
performance. That is very simple.

It is very simple, and you have it wrong.

Failed again. It is right it is just above.

As I said, you can't have it both ways.

Failed again.

There is nothing to be
gained with partitioning a heatbank
when a gas condensing boiler is
the sole source of energy.

Lots to be gained. A cheaper simpler boiler
and vastly reduced/elimination
of cycling.

There's nothing to be gained.

failed again.

You have added a bunch of complexity and achieved poorer efficiency.

Less complexity, as simple cheaper boiler is used.

You haven't saved any money either

No expensive 1.5K bpoioer to be bought.

Please provide a make and model
number of one of these "simpler boilers"
at around £400 Discounted
Heating prices, that is anywhere near the
quality of a WB Greenstar.

You have a thing about £400.

Further to that there is nothing to be
gained by having a heatbank in the
radiator part of the load at all in
this instance.

A heat bank a neutral point. A great advantage.

Only in circumstances where

a) multiple heat sources are being combined or

b) when there is a need to store heat because of the requirement of
large amounts to heat water, or

c) when the boiler, because of its sizing and limited or no control
range would naturally cycle.

This is not any of those cases.

It is. Even a modulating boiler cycles when demand is below the minimum kW.
With a heat bank, no cycling.

The boiler and rads operate
independently of each other. Constant flow can be through the boiler at
all
times.

That's clearly nonsense.

Failed again. The boiler and rads operate independently of each other.

The only way that they can operate truly
independently is by having two heat banks.
Are you advocating that now?

failed again.

The heat requirement into the cylinder will be quite different for DHW
vs. CH. In the former case, it will be maximum transfer after water
has been run. In the latter, either the heat will have to be fed in
at the rate of use (less than the boiler maximum output) or at full
power for short periods.

failed again. Full power for the re-heat time in one burn.

Where you have got the idea of constant flow from, goodness only
knows. If you mean constant water flow, regardless of demand, it is
going to be wasteful when neither CH nor DHW are demanding heat.


More failure. Boilers have an optimum flow through the heat exchanger.

No silly pressure diif valves needed. Rads with TRVs can be
virtually off and the boiler doesn't know or care.

There aren't anyway. If the pump is integral to the boiler,

Heating boilers don't have them integrated, well most don't.

the boiler's controller can match
it to the heat load.

Heating boilers with minimum control are used.

An exterior one can sense the flow
and pressure conditions and also reduce output.

The weather compensator, if integrated
with the boiler should move the
operating curve of the boiler up and down
to match the load.

This weather compensator is NOT
integrated with a boiler. This you can't
understand.

Oh good grief.

Sounds encouraging.

I am fully aware that this weather compensator is not integrated with
the boiler. That is why using this type with this application is
completely pointless.

Failed again.

I'm not repeating the obvious, and I'm certainly not about to educate
you about control systems.

Be sure, you will not educate me on control systems.

There are three useful applications for weather compensation:

a) An external, simple one of the type you describe, like the BEM5000,
which has analogue input sensors and a switched output which cycles
the boiler on and off. This is useful wih conventional, especially
older and possibly overpowered boilers where the hysteresis of the
built in thermostat is large and the boiler has a tendency to cause
the room temperature to overshoot; and the thermal characteristics of
the house tend to cause the same. This type of device reduces the
average radiator temperature by switching the boiler on and off rather
than letting its thermostat do the job. It's a crude system and may
make an improvement in this environment.

b) An external temperature sensor connected to a modulating,
condensing boiler's microprocessor. This type of controller already
has analogue inputs from the flow and return temperatures and can
control burn rate and even the pump. This additional sensor gives
additional data from the environment outside the house which will
affect the internal temperature after a time. The boiler can then
adjust accordingly as well as maintaining minimum power level and
temperature.

It isn't possible to achieve the same levels of control and efficiency
using method a) as this.

It is. When using heat bank.

Not if the controller is operating
the boiler by turning it on and
off, which it will have to do in the
case of a non modulating one.

Switches on - one long bur to setpoint - switches off. Simple.

This is how the BEM5000 works.
All that the heatbank is doing is to
add a lag in the control path.

failed again. not so.

c) A commercial system, where there is an external energy management
system having multiple analogue sensors inside and out, and able to
monitor the water temperatures. This type of controller is able to
control a boiler or boilers which are able to modulate, but by the use
of some kind of digital signal (PWM or coded), or via an analogue
control voltage or current (e.g. 4-20mA, 0-10v etc.)


Your proposal is for something that is basically a type a)
arrangement, but you are claiming that it is equivalent to or better
than type b) or c). This is patent nonsense.

None of your points has a heat bank incorporated, so squewed.

Again. All that the heatbank does is to
introduce a lag in the control system.
You can either choose to keep it topped up with heat
on a tight setpoint window, in which case the boiler will have to be
cycled a lot, or you can let the heatbank temperature drop by the use
of a wide window in which case it will cycle less and the radiator
temperatures will drop.

drop by not much at all.

If you switch to maintaining the temperature
of part of the heatbank to maintain a set point
according to the outside temperature, you
introduce a double control loop.

Nope.

Of course you do. One loop is from boiler to heatbank, the other
from heatbank via radiators to room.

Only one loop. Boiler to heat bank, dictated to by outsoide waether
conditions.

There is also the room thermostat or TRVs as an outer loop.

room stat? no there is not. TRVs are not in the boioere control loop.

The heatbank is not representative of the characteristics of the
radiator heat load.

It provides a mass of water at the temperaure the rads want. The heat bank
doesn't care about the rad heat load, it just provides the mass of water for
the rads to use.

All that you achieve at best is a rather poor
attempt at providing a heat source to the
radiators, the temperature
of which is varied according to outside conditions. THe boiler energy
manager, will attempt to maintain the heatbank temperature by cycling
the boiler on and off.

more failure

There is no value in doing that in comparison with a true modulation
of the boiler.

In the piece between the heatbank
and the boiler, if you use the
typical separate box type of weather
compensator, you will have an
analogue sensor for outside

Yes.

and one for inside,

?? One to sense the temp of the heat bank

plus an input for a
switched room thermostat.

Uh! Switched? room temp trimming is analogue unless to have a
cheapo.

take a look at the BEM5000. This is the common weather compensator
and is hardly cheap.

It is not the only model. It saves the cost of a 1.5K boiler.

Please provide an example
of a suitable weather compensating
controller at the same or lower price
than the BEM5000.

All the big makers make compensators at low prices.

Please also explain how you believe that on/off controlling a simple
boiler is more efficient than a modulating, condensing one.

Please read all of this thread again.

Please explain where the figure of £1.5k comes into this.
The discussion is around something like a WB Greenstar with price
point of £725. It's not good trying to justify your argument by
adding in £800 of cost which is irrelevant.

biolers with built-in load compensation modulation and waether compensation
are well north of 1K

THe arithmetic is between a good quality modulating boiler at £725 vs.
the cost of some alleged "simple" boiler at £400 plus your controls at
£300.

You are making things up.

It has a switched input for the room thermostat.

Not good if room influence is incorporated.

Exactly.

Contrast this to the Worcester Bosch Greenstar, which can have a
modulating room thermostat as an option for £42.

Only does one zone. A heat bank can have two zones fed from it. Each
zone
hits a neutral point.

This is irrelevant.

failed again. It isn't

The issue is still one of energy in vs. energy
out.

In and out of what? less energy into the boiler for energy out.

Microbore can be used when both go back to one
neutral point.

This is irrelevant as well. Microbore is simply a size of tube.
There is nothing magic about it.

Look up how microbore operates.

The inside analogue sensor would
normally be used on the boiler return,

Or boiler flow, which most operate on.
Used on the heat bank here.

Er no.

Er yes, depending on application.

Sigh.....


The important temperature for condensing efficiency is the
boiler return temperature

Lower the flow and the return follows suit.

Well obviously. Most modulating boilers that I have seen have both
flow and return sensors.


For other control applications this
is also commonplace because it
gives an indication of what the thermal
load is doing.

Using a heat bank the thermal load is irrelevant. The boiler doesn't
care
about it.

Oh dear. Of course it's relevant.

Not as far as the boioer is concerned.

THe DHW load is an overdraft on the heatbank of anything up to 200kW
for short periods of time. Boiler requirement to recharge is full
power, for a short time.

The CH load is likely to be 20-80% of full load according to demand
and is continuous during short to medium time periods.




The BEM5000 uses the sensor on the return.

Just an option they use.

It's pretty critical to the operation of the operation of the unit.

From the instructions:

"The ESMA must be mounted on a pipe connected to the boiler return
tapping, between the bypass and the boiler, using the clamping band
provided, in a position where it will sense the temperature of the
water returning from the HEATING circuit"

ESMA is the return sensor. It doesn't say *may* but *must*.

Regarding the room thermostat it uses the words

"If a room thermostat is used....."

i.e. optional.



but could be used on the return
from the radiators to the heatbank.

Could be on the cylinder not far from
the boiler/rads returns pipes.

That makes it even worse.

failed. makes it better as it sense the mass of water, which is at the
temp
the building requires.

The mass of water will be at some temperature. The controller should
be trying to measure the radiator return temperature in your example
because that represents something derived from the heat load into the
space. The temperature of the heatbank is not well related to that.


The temperature of the cylinder wall is
only vaguely related to the return pipes
and will have a time lag.

The boiler doesn't want to know the rads return temperature. I doesn't
care.

In the case of your external controller and full power switched boiler
set up, obviously not. The closest would be that the controller
wants to know the return temperature from the radiators.

However the exercise is pointless because it will be worse than
letting a controller in the boiler do the job.



Neither is ideal because
connecting it to the radiator
return means that the controlled device
(boiler) has the damping effect of the
heatbank in between which will
adversely influence the control loop.
Having it on the boiler return
means that the temperature being monitored
relates to heat use by the
heatbank and not the room space.

It is clear you do not understand.

It's clear that I do,

No. It is clear you do not understand.

It's behind you.......


and that your scheme gets more an more
complicated and less useful/

It is simple. It also works very well indeed.

Have you implemented and measured this in comparison to a modulating
condensing boiler connected to radiators directly?

If so, which boiler and controller did you use for each?



The rad circuits are off the bottom of
the heat bank and have their own pump. Easy.

An extra pump.

That will break the bank.

None of this breaks the bank.

The point is that you are proposing an unnecessarily complicated
system, which patently can't perform as well as one with analogue
sensing of water temperatures and modulation of the burner.

You are unable to provide types and prices of components for this that
will come in at under the price point for a modulating system.



The boilers flow and return
is off the heat bank, at the bottom of the heat bank. The
compensator
has
a probe on the bottom section of the heat bank producing a mass of
water
at
the temp the rads require. The lower temp at the bottom on part load
will
ensure low temp return for high efficient condenser operation, with an
expensive complex boiler.

I presume that you mean without an expensive complex boiler.

yep.

Do you think that the Greenstar at £725 is expensive?

Not bad for what it is. Others are cheaper. This is besides the point.

Not really. You can get modulating, condensing boilers for a bit
less than this, or a bit more.

What is the make and model number of your alleged "simple" boiler,
with equivalent build quality to this?



If you take off the £300 or so needed
to implement your scheme, plus
the poorer long term reliability because
of the extra components,

You have a simpler boiler with less components.

They are all external in various boxes, valves and extra pumps.



Since the external box weather
compensator is going to turn the boiler
on and off to maintain the temperature,
it will not run at its most efficient.

failed again.

You would be trying to match a (say) 30kW boiler into a
(say) 10kW load. The boiler cannot run efficiently like that.

You fail to understand. A mass of water is heated to a temp a
compensator
dictates. The mass of water is heated and the rads take off as much heat
as
they need. Wheh the mass of water needs heating the 30kW boiler reheats
the
mass. The boiler know or care about loads of rad circuit.

No you fail to understand.

The equations are simple.

In the modulating, condensing boiler case, if the load to the
radiators needs to be 10kW, the boiler will drop down to that output
level and a low running temperature, continuously. There will be no
cycling at all and the boiler will be running well into into the
higher efficiency part of its operating curve.

In your simple boiler case, the 10kW load match will have to be
achieved (assuming a 30kW boiler) by running it at full power for a
third of the time. This is less efficient, a) because the boiler
is going on and off and b) because it is not operating on the most
efficient part of the curve.
You can make those on/off periods shorter or longer by how large you
make the allowable temperature drop in the heatbank, but it will
average to a 3:1 off/on.



You have to know what you are controlling
before you apply control. You
don't.

It is very obvious what is being controlled.
One part is the room temperature.

The room temp influence only trims.

This depends on the thermal characteristics of the building.

It doesn't, it depends on what compensator you use.

Oh really. What kind of compensator do you have in mind?

It is possible to run a modulating boiler purely based on outside
temperature measurement, but the effect will be that the inside
temperature will tend to fluctuate.



The other part is controlling
the boiler firing level
most efficiently to match the room
requirement.

No. Get the boiler to heat a mass of
water all at one time, to what
temperature the room requires.

This is why your approach is nonsense.

failed again. See above

Sigh.


If you were to connect the
modulating boiler directly to the
radiators, an average flow temperature
will be in the 50 degree area.

Once the buildings heat demand is below the minimum of the boiler cycling
starts.

Obviously. However it is far better if it cycles between 0 and 20%
of full load than 0 and 100%


If you try to do this via part of a
heatbank and set that temperature,
there is relatively little energy storage -
the typical volume of
water is perhaps half of the radiator capacity.

You make sure the storage is at least x 2 of rads.

So let's see. My radiators and pipework have a capacity of about
100 litres.

So now you are saying that I need a 200 litre heatbank for this; and
the one for the hot water in addition to that?

Plus I get worse performance and efficiency than a boiler connected
directly to them?

Why would I want to do that?




Very soon, the water temperature in
the heatbank will have fallen and
the boiler has to come on again.

Getting it.

In effect, you are making it cycle
by having regular relatively short full power burns.

No. short power burns at lomng intervals.

The energy still has to be put in.

With a 200 litre cylinder that will be about 30 mins on - I wouldn't
call that short.

It is also not a practically good example because the heatbank has
been run to zero in the intervening time.


This is not as efficient as
letting the boiler run continuously at the
temperature required for the radiators.

failed again.

Do you have figures which demonstrate that running a condensing boiler
at full power with cycling is more efficient than running it on part
power continuously?

If your case were more efficient, why do you imagine that the
manufacturers of modulating boilers arrange them to drop the power and
temperature as the load reduces? Do you imagine that British Gas
sponsors them to use more energy??



In the case of a
modulating, condensing boiler,

No need for a modulating condensing boiler.

There are very few quality ones that don't.

Most do modulate, but heating
boilers modulate on flow setpoint temp.

... and also account for the return temperature.

As the boiler will be on full, when
heating the mass of water for CH
very rare will it modulate.

It will be cycling inefficiently instead.

failed again. Not so.

Not only that, the radiator temperatures
will be fluctuating as well.

Fluctuation of rad temps would be minimum.

Not if you run the temperature in the heatbank down.

What do you believe that the operating window of the heatbank should
be and why?


Fundamentally, you can either
let the heatbank cool right down and
reheat it at full power which causes
the boiler to run less efficiently

failed again. the boiler runs efficiently. as the mass of water is to
the
temp the building requires.

So are you saying that you want to maintain the heatbank at close to
the setpoint temperature or allow it to fall?

If so, by how much?




it also screws up the primary purpose
of the heatbank, which is to
provide an energy store to deliver
large amounts of energy quickly to
a heat exchanger.

Primary?

And to prevent boiler cycling and giving on-demand mains pressure hot
water.
Eliminating cold water storage tanks.

That is implicit in what I said.

With a heat bank the DHW and CH
circuits don't care about the boiler.

They have totally different characteristics.

Which is a great advantage. Divide and rule.

That's your best argument so far. It's a pity that it bears no
relationship whatever to the subject matter.




The DHW application needs
large amounts of heat for relatively short
periods of time. That is why it is
called a heat *bank*.

failed again. It is called a heat bank because it is a bank of heat.

That's helpful :-)



It allows overdrafts relative to the
capabilities of the boiler.

The CH application requires much
smaller amounts of heat on a
continuous basis with quite slow rates of change of demand.

The boiler can be controlled more
efficiently by having it heat one mass of water very quickly and in
one
long
efficient burn.

That is only true for the DHW case.

failed again. applicable to CH.

This depends on the temperature range that you are going to use.

Are you going to try to maintain the set point or allow the
temperature to fall?



We have already established for
a condensing boiler that it will run more
efficiently at lower temperatures

Good. getting better.

and power levels continuously than
by switching on and off.

Failed again. Continuous power levels when burning in one long efficient
burn.

It will be more efficient at lower temperatures and power levels.
With your proposed simple boiler, this doesn't happen.



For the DHW application, the main
purpose of a long burn at high power
level is to transfer as much energy as
possible back into the cylinder
as fast as possible.

Good.

Taken further it can heat two masses
of water at different
temperatures.

So now we have two heatbanks?

One split into two separte temperature zones.

With what? Some kind of divider or just relying on stratification?

If it's the latter, you are going to get a big interaction between the
performance requirement of the hot water vs. your desired control for
the CH part. Since the characteristics are completely different, you
will end up with a poor compromise.


High for DHW and low for CH.
Taken further again, the CH mass
of water can be at variable temperatures
to what the outside weather
dictates. When called to heat the CH
mass of water it does it in one long
burn no matter what temperature
the CH water mass is.

The burn and cycle time will vary
with the rate of use of energy and
the amount of temperature drop
allowed before reheating is initiated.
This is far from efficient.

Efficient for the boiler usage.

Whatever that means, which is not a lot.



A BEM5000 costs £188

A diverter valve costs £56

You forgot the extra pump to run the radiator circuit - £56 for a
Grundfos

All prices from Discounted Heating. Total cost is £311.

You can buy a Worcester Greenstar 28HE for £725 from them.

What 28kW condensing boiler you going to buy from Discounted Heating
for £410 that is any good?

But you save a wedge on a 1.5K load compensating boiler and much
simpler.

Where did you get £1.5k from?

A load compensating modulation, outside waether compensating boioer is
about
1K

You introduced the idea of weather compensation as a means to control
the heatbank temperature, just so that you could hook up the radiators
to it - a completely pointless exercise.

Using a heat bank load compensating modulation is not required.

You can equally argue that with a modulating boiler with a room
temperature analogue sensor that outside weather compensation isn't
required.

You should find out the advantage of weather compensation.

So you mean a non modulating boiler?

Yes.

These are not as efficient as
modulating types by definition,

failed again. They are. It depends on how it is controlled and what
conditions it is run in.

Certainly with your suggested method of on off control it is not going
to run at anything like the efficiency of a modulating model using its
own temperature sensing.

failed again. more efficient.

Poor show only 1/10.

IMM wrote:

2/10. very poor mark. You should feel ashamed of yourself.

Give up DIMM, you are so out of your depth it is comical.

--
Cheers,

John.

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| John Rumm - john(at)internode(dot)co(dot)uk |
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On Sat, 4 Sep 2004 21:53:07 +0100, "IMM" wrote:

..

It does if it is going to be involved
in an efficient control system
where the heat output to the radiators
and the heating space are
measured

They are measured by the weather compensator, with any room temp influence
to drop the slope if need be.

It should be the other way round of course. We are not trying to
control the weather here, but the temperature in the house.
The outside temperature is monitored to provide a correction to the
slope.



and controlled without lag,
then it most certainly does.

No lag. A mass of water the temperature required is available.

OK, so you don't understand the meaning of the term "lag" in a control
system. There is no point in discussing its influence in that case.




I said *may*, and it will only be in so
far as a difference between an
analogue sensor on the cylinder
and a thermostat with substantial
hysteresis on the boiler.

Thermostat on the boiler is on full, and will rarely cut out on this.

OK, so this means that you are relying on the external weather
compensator, which is controlling the boiler by switching.





So are you saying that the external
controller doesn't control the
boiler by turning it on and off.

No.

That's good. I just wanted to be clear on that.



You'll be telling me that it
operates a motor on the gas tap next.

Nope I will not.

That's a relief.


and b) not operating
at the optimum temperature

Failed again.

If it is a condensing boiler, on/off control with full output or
nothing will not operate it efficiently.

You fail to understand condensing boilers, or boilers at all.

It seems that I understand rather more than you do.

A boiler will
only raise water a certain temperature with a given flowrate through the
heat exchanger.

Correct - actually it's more like maximum temperature.

The flow through it can be constant, as no TRVs used. If
say at x flowrate it raises the water 25C, if the return is 30C only 55C
come out of the flow. Way below the boiler stat set to 82C. When the mass
of water is heated the boiler stat would have never have cut in to cycle the
boiler, so one long efficient burn.

Obviously the boiler won't be cycling on its internal thermostat,
assuming it is set high. It will be being switched by the fact
that the rate of heat production will exceed the use by the CH.
This cannot be as efficient as running the boiler continuously at the
level of the radiator heat load. You are also assuming an ideal
(in the engineering sense) heatbank where there is no mixing and
churning of the internal water. This will have the effect of
raising the temperature sensed by your controller higher than it would
otherwise be and reducing the run time. If the return were directly
from the radiators there would be much less mixing and the return
temperature is therefore much more indicative of the actual real load.




- unless you are talking about a
non-condensing boiler as well, of course.

If you use a modulating boiler
and attempt to control it in an on/off
fashion as an external simple weather
compensator will try to do, then
the efficiency will be worsened as
compared with allowing the boiler
to monitor the radiator water temperature
directly.

Failed again. When on it heats a large
mass of water. This confuses you.
That is sad.

The trouble is that it doesn't.

You are rarther silly now.

If that is your best reply, then there is no point in discussing the
point further.


On the one hand you are saying that you are going to have part of a
heatbank operating at a set point and being maintained that way by
controlling the heat going in. By definition, if you do that with a
non-modulating boiler with power output level larger, probably
substantially larger than the rate of use by the radiators, then you
will have to cycle the boiler.

The boiler does not cycle when re-heating the mass. Operation: heats the
mass of water mass cools - mass is reheated all at once with "no" boiler
cycling - heat extracted from the water mass by the rad circuit - mass is
reheated all at once with "no" boiler cycling .

This is physically impossible. If the heat input from the boiler is
greater than the heat use and you are not modulating the boiler
output, by definition your controller has to cycle it off and then
back on again. This is less efficient than matching the boiler
output accurately to the load.




not because of running temperatures). If you do that, you
are going to have to let the heatbank (or part thereof in use)
discharge all of its heat before running the boiler again.
This will result in cooling and heating of the radiators, a
fluctuation in heat output and a variation in room temperature.

Any fluctuation would be minimal.

That will depend on how you set the operating window of the heatbank.

the mass of water takes time to cool.

It will cool at the rate determined by the use through the radiator
circuit.


It
is not like hot water running though a rad circuit return pipe. very little
mass and less mass in the whole rad circuit than in the stored water mass by
at "least" half as much. The water mass stabilises operation.

It simply causes control lag, but I know that you don't understand the
concept. I know that you don't know what "mass" means.

Your supposition assumes that the volume of water in the heatbank is
twice that of the radiators and pipes. Are you seriously suggesting
installing a 200l heat bank just to run the radiators?


You can't have it both ways.

The element that is intended to be
controlled is the room
temperature, not the water temperature
of the heatbank.

Your comprehension is poor. The boiler/heat bank
maintain the lowers section
of the heat bank at the temperature that
the rads require for optimum
performance. That is very simple.

It is very simple, and you have it wrong.

Failed again. It is right it is just above.

As I said, you can't have it both ways.

Failed again.

It seems that you have,



You have added a bunch of complexity and achieved poorer efficiency.

Less complexity, as simple cheaper boiler is used.

Plus an extra controller, an extra pump, valves and sensors.



You haven't saved any money either

No expensive 1.5K bpoioer to be bought.

The only person who raised the subject of £1500 or £1000 boilers was
you in an attempt to divert attention away from your farcical idea.
Sorry, but it won't wash.

You also introduced the idea of an external boiler controller using an
outside sensor and applied in a way for which it wasn't designed and
controlling a boiler in an inappropriate way. You can't even find
one that is suitable for what you think you are trying to do.


Please provide a make and model
number of one of these "simpler boilers"
at around £400 Discounted
Heating prices, that is anywhere near the
quality of a WB Greenstar.

You have a thing about £400.

I do, because that is the comparison point; not your £1500 figure.




Further to that there is nothing to be
gained by having a heatbank in the
radiator part of the load at all in
this instance.

A heat bank a neutral point. A great advantage.

Only in circumstances where

a) multiple heat sources are being combined or

b) when there is a need to store heat because of the requirement of
large amounts to heat water, or

c) when the boiler, because of its sizing and limited or no control
range would naturally cycle.

This is not any of those cases.

It is. Even a modulating boiler cycles when demand is below the minimum kW.

Yes of course it does, but at that point - usually around 4-7kW, it
doesn't matter anyway. In practice, this only happens for a very
short period anyway.


With a heat bank, no cycling.

It is cycling because the controller is switching it off and on, and
as part of the normal operation. It *always* does this.


The boiler and rads operate
independently of each other. Constant flow can be through the boiler at
all
times.

That's clearly nonsense.

Failed again. The boiler and rads operate independently of each other.

Once again your normal MO when you don't understand something -
selectively clip.

It is anyway irrelevant if the flow is continuous through the boiler -
there aren't any sensors as there are with a modulating boiler.



The only way that they can operate truly
independently is by having two heat banks.
Are you advocating that now?

failed again.

So is it two heatbanks or one?



The heat requirement into the cylinder will be quite different for DHW
vs. CH. In the former case, it will be maximum transfer after water
has been run. In the latter, either the heat will have to be fed in
at the rate of use (less than the boiler maximum output) or at full
power for short periods.

failed again. Full power for the re-heat time in one burn.

Sigh.... Until the heatbank depletes, the thermostat on the cylinder
comes on and the boiler runs again, then goes off because the
thermostat is satisfied, ad infinitum. This is cycling.


Where you have got the idea of constant flow from, goodness only
knows. If you mean constant water flow, regardless of demand, it is
going to be wasteful when neither CH nor DHW are demanding heat.


More failure. Boilers have an optimum flow through the heat exchanger.

Which is obviously dependent on the rate of heat production for
optimised results and why some modulating boilers also modulate the
pump.

You have not only a switched boiler, but one which always runs at full
power and with the same flow rate. Three efficiency reducing factors.


No silly pressure diif valves needed. Rads with TRVs can be
virtually off and the boiler doesn't know or care.

There aren't anyway. If the pump is integral to the boiler,

Heating boilers don't have them integrated, well most don't.


The term is semantic, which is why I was careful to say "integral
pump".




I'm not repeating the obvious, and I'm certainly not about to educate
you about control systems.

Be sure, you will not educate me on control systems.

Believe me, I reached that conclusion a very long time ago!!.




Not if the controller is operating
the boiler by turning it on and
off, which it will have to do in the
case of a non modulating one.

Switches on - one long bur to setpoint - switches off. Simple.

Yep. Simple cycling.


This is how the BEM5000 works.
All that the heatbank is doing is to
add a lag in the control path.

failed again. not so.

There's little else



c) A commercial system, where there is an external energy management
system having multiple analogue sensors inside and out, and able to
monitor the water temperatures. This type of controller is able to
control a boiler or boilers which are able to modulate, but by the use
of some kind of digital signal (PWM or coded), or via an analogue
control voltage or current (e.g. 4-20mA, 0-10v etc.)


Your proposal is for something that is basically a type a)
arrangement, but you are claiming that it is equivalent to or better
than type b) or c). This is patent nonsense.

None of your points has a heat bank incorporated, so squewed.

Again. All that the heatbank does is to
introduce a lag in the control system.
You can either choose to keep it topped up with heat
on a tight setpoint window, in which case the boiler will have to be
cycled a lot, or you can let the heatbank temperature drop by the use
of a wide window in which case it will cycle less and the radiator
temperatures will drop.

drop by not much at all.

It will drop by what you want it to drop by. Either you can maintain
the temperature near the set point and the boiler will cycle more
frequently, or you can allow a larger drop and the radiator
temperatures will drop.




If you switch to maintaining the temperature
of part of the heatbank to maintain a set point
according to the outside temperature, you
introduce a double control loop.

Nope.

Of course you do. One loop is from boiler to heatbank, the other
from heatbank via radiators to room.

Only one loop. Boiler to heat bank, dictated to by outsoide waether
conditions.

There is also the room thermostat or TRVs as an outer loop.

room stat? no there is not. TRVs are not in the boioere control loop.

The TRVs are in the second control loop. If you remember, you
earlier said that there was only one loop. In fact in your scheme,
there are at least three.




The heatbank is not representative of the characteristics of the
radiator heat load.

It provides a mass of water at the temperaure the rads want. The heat bank
doesn't care about the rad heat load, it just provides the mass of water for
the rads to use.

You're running round in ever decreasing circles now. Earlier you
made a big point about the external weather compensator maintaining an
appropriate temperature for the radiators. Now you are saying that
it doesn't matter. You can't make up your mind whether you want the
heatbank temperature to be maintained or rise and fall dramatically.

In short you are guessing.


es.

It is not the only model. It saves the cost of a 1.5K boiler.

Please provide an example
of a suitable weather compensating
controller at the same or lower price
than the BEM5000.

All the big makers make compensators at low prices.

I see. Please name some and provide the prices.


Please also explain how you believe that on/off controlling a simple
boiler is more efficient than a modulating, condensing one.

Please read all of this thread again.

You have got to be joking.



Please explain where the figure of £1.5k comes into this.
The discussion is around something like a WB Greenstar with price
point of £725. It's not good trying to justify your argument by
adding in £800 of cost which is irrelevant.

biolers with built-in load compensation modulation and waether compensation
are well north of 1K

This is not the comparison that we are making. The simple solution
was of a modulating boiler running the radiators directly. You have
added in all the complexity of weather compensators hooked up to
external controllers whose purpose is to switch cycle old
non-modulating boilers in an attempt to make them a bit more efficient
in the system.

Clearly a modulating boiler with an external temperature sensor
directly hooked in is going to outperform one without and certainly
your scheme. Therefore there is little point in doing a comparison
on this basis.



THe arithmetic is between a good quality modulating boiler at £725 vs.
the cost of some alleged "simple" boiler at £400 plus your controls at
£300.

You are making things up.

You're looking in the wrong place. You're trying to alter the basis
of the discussion to a different price point and different
functionality and efficiency.

Stick to the question. Where are these simple £400 good quality
boilers?




The issue is still one of energy in vs. energy
out.

In and out of what? less energy into the boiler for energy out.

The heatbank, obviously.


Microbore can be used when both go back to one
neutral point.

This is irrelevant as well. Microbore is simply a size of tube.
There is nothing magic about it.

Look up how microbore operates.

I know full well how microbore operates. It's copper tube. End of
story.



The inside analogue sensor would
normally be used on the boiler return,

Or boiler flow, which most operate on.
Used on the heat bank here.

Er no.

Er yes, depending on application.

Sigh.....


The important temperature for condensing efficiency is the
boiler return temperature

Lower the flow and the return follows suit.

Well obviously. Most modulating boilers that I have seen have both
flow and return sensors.


For other control applications this
is also commonplace because it
gives an indication of what the thermal
load is doing.

Using a heat bank the thermal load is irrelevant. The boiler doesn't
care
about it.

Oh dear. Of course it's relevant.

Not as far as the boioer is concerned.

Not directly because your boiler has no sensors. Taking the system as
a whole, it is highly relevant.





You introduced the idea of weather compensation as a means to control
the heatbank temperature, just so that you could hook up the radiators
to it - a completely pointless exercise.

Using a heat bank load compensating modulation is not required.

You can equally argue that with a modulating boiler with a room
temperature analogue sensor that outside weather compensation isn't
required.

You should find out the advantage of weather compensation.

I know the advantages of weather compensation, properly implemented,
quite well, thanks. I have such an arrangement, remember.
I also have the ability to log precisely what the boiler is doing in
terms of burn rate, fan operation, pump operation and 6 different
system temperatures.



So you mean a non modulating boiler?

Yes.

These are not as efficient as
modulating types by definition,

failed again. They are. It depends on how it is controlled and what
conditions it is run in.

Certainly with your suggested method of on off control it is not going
to run at anything like the efficiency of a modulating model using its
own temperature sensing.

failed again. more efficient.


Then please explain why the boiler manufacturers engineer their
products to modulate the burner down and reduce temperature and pump
speed when less energy is required. Clearly you know something that
they don't.

Go away and do some reading up on condensing boiler technology and
control systems. Come back when you've understood it and we can run a
short test. Shall we set the date in 2014 now?




..andy

To email, substitute .nospam with .gl

"John Rumm" wrote in message
...
IMM wrote:

2/10. very poor mark. You should feel ashamed of yourself.

Give up DIMM, you are so out of your depth it is comical.

What is this, are you trying to take Maxies bird Dimm Lin the faa eastern
luscious lovely? 0/10 for you, you third worlder.

In message , IMM writes

"John Rumm" wrote in message
...
IMM wrote:

2/10. very poor mark. You should feel ashamed of yourself.

Give up DIMM, you are so out of your depth it is comical.

What is this, are you trying to take Maxies bird Dimm Lin the faa eastern
luscious lovely? 0/10 for you, you third worlder.

I don't think DIMMs out of his depth, he's already drowned

--
geoff

"raden" wrote in message
...
In message , IMM writes

"John Rumm" wrote in message
...
IMM wrote:

2/10. very poor mark. You should feel ashamed of yourself.

Give up DIMM, you are so out of your depth it is comical.

What is this, are you trying to take Maxies bird Dimm Lin the faa eastern
luscious lovely? 0/10 for you, you third worlder.

I don't think DIMMs out of his depth, he's already drowned

Maxie, how are you? When are you off into the wild blue yonder?

"Andy Hall" wrote in message
...
On Sat, 4 Sep 2004 21:53:07 +0100, "IMM" wrote:

It does if it is going to be involved
in an efficient control system
where the heat output to the radiators
and the heating space are
measured

They are measured by the weather
compensator, with any room temp influence
to drop the slope if need be.

It should be the other way round of course.

failed again.

We are not trying to
control the weather here, but the
temperature in the house.

You don't say.....

The outside temperature is monitored
to provide a correction to the slope.

failed again. I'm fed up marking you as it's always a poor score. The
outside weather gives the slope and the internal temp sensor (if one fitted.
Many internal temp sensors can be fitted and the temps averaged on large
buildings) raise or lowers it to suit.

For you:

1. With heat bank and a weather compensator, a mass of water is heated at
the bottom of a heat bank to the temperature what the building requires (the
rads). The temp can be anything from 25C to 80C depending on the outside
conditions. The temp of the lower mass of water is dictated by the weather
compensator, which is near enough the correct temperature that the rads will
require.

2. A load compensating modulating boiler generally goes down to about
5-7kW, any lower than that it cycles on-off. Some super expensive boilers
go down to 3kW. As most of the time buildings are up to temp (part load on
the heating system) this will be significant cycling in most modulating
boilers. These boilers tend to be complex and expensive and have more
expensive parts and servicing to go wrong on them.

- With a heat bank the rad circuit(s) can draw-off only 1 kW of heat from
the heat bank and no cycling from the boiler. Only when the whole mass of
water cools does the boiler come in and re-heat the mass of water in one
long efficient no boiler cycling burn.

- The temp of the mass of water is not totally fixed as the temp will drop
slightly as the mass of water is cooling. This is insignificant and TRVs
trim off local temps. Weather compensating slopes are never fully accurate
and may out by +-5%. The slope is a best fit at the best of times. An
internal temp sensor (if one fitted), raise or lowers the slope it to suit.
Many internal temp sensors can be fitted and the temps averaged on large
buildings for greater accuracy..

- A simpler, and cheaper, condensing boiler can be used, similar to any
regular heating boiler, that can have the optimum flow through the boiler
at all times for greater efficiency and boiler longevity.

- A variable speed Alpha pump can be used on the rad circuits reducing noise
electricity consumption.

- If having a heat bank for DHW, then increasing the size to provide:
* a cheaper, simpler and more reliable boiler,
* a neutral point for all circuits,
* weather compensation
* elimination of boiler cycling when on part load, which gives far greater
boiler longevity on all components.
* oversized rads to cope with a condensing boiler giving lower return
temperatures.
* Variable speed pumps(s) on rad circuits.
* instant heat available first things in the mornings. Rads are fully
heated with afew minutes.

Now understand this if you can. It is not difficult. If there are parts
you are confused about, just accept it as right.

"raden" wrote in message
...
In message , IMM writes

"John Rumm" wrote in message
...
IMM wrote:

2/10. very poor mark. You should feel ashamed of yourself.

Give up DIMM, you are so out of your depth it is comical.

What is this, are you trying to take Maxies bird Dimm Lin the faa eastern
luscious lovely? 0/10 for you, you third worlder.

I don't think DIMMs out of his depth, he's already drowned

Maxie, has Dimm Lin the far eastern luscious lovely been involved in beach
accident? I am sorry to hear this.

On Sun, 5 Sep 2004 10:51:52 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Sat, 4 Sep 2004 21:53:07 +0100, "IMM" wrote:

It does if it is going to be involved
in an efficient control system
where the heat output to the radiators
and the heating space are
measured

They are measured by the weather
compensator, with any room temp influence
to drop the slope if need be.


It should be the other way round of course.



The outside temperature is monitored
to provide a correction to the slope.

failed again. I'm fed up marking you as it's always a poor score.

That's good. You weren't invited to in the first place.

The
outside weather gives the slope and the internal temp sensor (if one fitted.
Many internal temp sensors can be fitted and the temps averaged on large
buildings) raise or lowers it to suit.

We are talking about a simple domestic system here, not a commercial
one



For you:

1. With heat bank and a weather compensator, a mass of water is heated at
the bottom of a heat bank to the temperature what the building requires (the
rads). The temp can be anything from 25C to 80C depending on the outside
conditions. The temp of the lower mass of water is dictated by the weather
compensator, which is near enough the correct temperature that the rads will
require.

So the boiler will be put into a situation where it will cycle
frequently when the heatbank temperature is low.

You still haven't suggested a suitable controller.


2. A load compensating modulating boiler generally goes down to about
5-7kW, any lower than that it cycles on-off. Some super expensive boilers
go down to 3kW.
As most of the time buildings are up to temp (part load on
the heating system) this will be significant cycling in most modulating
boilers.

This is based on a bunch of assumptions which in practice are not the
case.

Also, any cycling that does happen will be at the bottom of the
modulating range and not full power as in your example.
This makes a substantial difference.

These boilers tend to be complex and expensive and have more
expensive parts and servicing to go wrong on them.

This is untrue. The extra complexity is in the firmware of the
controlling microprocessor. There are no additional mechanical
components



- With a heat bank the rad circuit(s) can draw-off only 1 kW of heat from
the heat bank and no cycling from the boiler. Only when the whole mass of
water cools does the boiler come in and re-heat the mass of water in one
long efficient no boiler cycling burn.

Of course there will be cycling.

You still haven't said whether you are going to maintain the heatbank
at the setpoint or allow the temperature to drop to practically room
temperature.



- The temp of the mass of water is not totally fixed as the temp will drop
slightly as the mass of water is cooling.

How much is "slightly"?


This is insignificant and TRVs
trim off local temps.

Only if the heat being provided by the water is within the range
required and controllable by the TRV. Since you haven't indicated
what that will be, this suggestion is guesswork.

Weather compensating slopes are never fully accurate
and may out by +-5%. The slope is a best fit at the best of times.

5% accuracy on a system for domestic use is pretty good/

It may well be like this or worse on an external box controller such
as you describe because the controlled device is an unknown

If you have an external sensor connected to a boiler designed with
weather compensation and for use with a nominated sensor, then all the
pieces can be matched together as a system and will produce a much
better result than can be achieved by throwing bits and pieces
together - especially cheap ones as you are suggesting.

By the way, what about that controller?


internal temp sensor (if one fitted), raise or lowers the slope it to suit.
Many internal temp sensors can be fitted and the temps averaged on large
buildings for greater accuracy..

We are talking about a house, not a commercial building.


- A simpler, and cheaper, condensing boiler can be used, similar to any
regular heating boiler, that can have the optimum flow through the boiler
at all times for greater efficiency and boiler longevity.

Where is this cheaper boiler? Where is the £400 model that you are
dying to tell us about?

How are you going to control the flow to optimise it?



- A variable speed Alpha pump can be used on the rad circuits reducing noise
electricity consumption.

A modulating pump is always a good idea to match heat source and load.
Better yet if incorporated into the boiler and controlled by its
microprocessor.



- If having a heat bank for DHW, then increasing the size to provide:
* a cheaper, simpler and more reliable boiler,

Which one? I'm still waiting.

How big is this heatstore going to be?

At least 100 litres is needed for the DHW, and 200litres for the space
heating. What about the space for these cylinders?

Normally you are squeaking about space saved by combis. Now you are
proposing a half baked, unreliable system with huge space
requirements.

* a neutral point for all circuits,

Only a benefit if there are multiple heat sources.

* weather compensation

Except that your suggestion does it poorly in comparison with a full
integrated modulating boiler.


* elimination of boiler cycling when on part load, which gives far greater
boiler longevity on all components.

It does not eliminate boiler cycling because the damned thing is being
switched on and off.


* oversized rads to cope with a condensing boiler giving lower return
temperatures.

If possible one should always do that with condensing boilers if
possible.

How is your system going to cope with heat output required for
different radiator design schemes? It is not monitoring the return
temperature.


* Variable speed pumps(s) on rad circuits.

Even better if one is integrated with the boiler and controlled by it.


* instant heat available first things in the mornings. Rads are fully
heated with afew minutes.

The same happens with a modulating boiler.

It is better if th control system can monitor the room temperature and
back off the heat supply at the right time.

If you dump heat from a store directly into radiators when it has been
a cold night and presumably the heatbank temperature is high, you are
going to get huge overshoot and waste of heat.



Now understand this if you can. It is not difficult. If there are parts
you are confused about, just accept it as right.

I am not and have never been confused.

Perhaps you would like to answer the questions that you have been
avoiding.


..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Sun, 5 Sep 2004 10:51:52 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Sat, 4 Sep 2004 21:53:07 +0100, "IMM" wrote:

It does if it is going to be involved
in an efficient control system
where the heat output to the radiators
and the heating space are
measured

They are measured by the weather
compensator, with any room temp influence
to drop the slope if need be.


It should be the other way round of course.



The outside temperature is monitored
to provide a correction to the slope.

failed again. I'm fed up marking you as it's always a poor score.

That's good. You weren't invited to in the first place.

The
outside weather gives the slope and the internal temp sensor (if one
fitted.
Many internal temp sensors can be fitted and the temps averaged on large
buildings) raise or lowers it to suit.

We are talking about a simple domestic system here, not a commercial
one



For you:

1. With heat bank and a weather compensator, a mass of water is heated
at
the bottom of a heat bank to the temperature what the building requires
(the
rads). The temp can be anything from 25C to 80C depending on the outside
conditions. The temp of the lower mass of water is dictated by the
weather
compensator, which is near enough the correct temperature that the rads
will
require.

So the boiler will be put into a situation where it will cycle
frequently when the heatbank temperature is low.

You still haven't suggested a suitable controller.


2. A load compensating modulating boiler generally goes down to about
5-7kW, any lower than that it cycles on-off. Some super expensive
boilers
go down to 3kW.
As most of the time buildings are up to temp (part load on
the heating system) this will be significant cycling in most modulating
boilers.

This is based on a bunch of assumptions which in practice are not the
case.

Also, any cycling that does happen will be at the bottom of the
modulating range and not full power as in your example.
This makes a substantial difference.

These boilers tend to be complex and expensive and have more
expensive parts and servicing to go wrong on them.

This is untrue. The extra complexity is in the firmware of the
controlling microprocessor. There are no additional mechanical
components



- With a heat bank the rad circuit(s) can draw-off only 1 kW of heat from
the heat bank and no cycling from the boiler. Only when the whole mass
of
water cools does the boiler come in and re-heat the mass of water in one
long efficient no boiler cycling burn.

Of course there will be cycling.

You still haven't said whether you are going to maintain the heatbank
at the setpoint or allow the temperature to drop to practically room
temperature.



- The temp of the mass of water is not totally fixed as the temp will
drop
slightly as the mass of water is cooling.

How much is "slightly"?


This is insignificant and TRVs
trim off local temps.

Only if the heat being provided by the water is within the range
required and controllable by the TRV. Since you haven't indicated
what that will be, this suggestion is guesswork.

Weather compensating slopes are never fully accurate
and may out by +-5%. The slope is a best fit at the best of times.

5% accuracy on a system for domestic use is pretty good/

It may well be like this or worse on an external box controller such
as you describe because the controlled device is an unknown

If you have an external sensor connected to a boiler designed with
weather compensation and for use with a nominated sensor, then all the
pieces can be matched together as a system and will produce a much
better result than can be achieved by throwing bits and pieces
together - especially cheap ones as you are suggesting.

By the way, what about that controller?


internal temp sensor (if one fitted), raise or lowers the slope it to
suit.
Many internal temp sensors can be fitted and the temps averaged on large
buildings for greater accuracy..

We are talking about a house, not a commercial building.


- A simpler, and cheaper, condensing boiler can be used, similar to any
regular heating boiler, that can have the optimum flow through the
boiler
at all times for greater efficiency and boiler longevity.

Where is this cheaper boiler? Where is the £400 model that you are
dying to tell us about?

How are you going to control the flow to optimise it?



- A variable speed Alpha pump can be used on the rad circuits reducing
noise
electricity consumption.

A modulating pump is always a good idea to match heat source and load.
Better yet if incorporated into the boiler and controlled by its
microprocessor.



- If having a heat bank for DHW, then increasing the size to provide:
* a cheaper, simpler and more reliable boiler,

Which one? I'm still waiting.

How big is this heatstore going to be?

At least 100 litres is needed for the DHW, and 200litres for the space
heating. What about the space for these cylinders?

Normally you are squeaking about space saved by combis. Now you are
proposing a half baked, unreliable system with huge space
requirements.

* a neutral point for all circuits,

Only a benefit if there are multiple heat sources.

* weather compensation

Except that your suggestion does it poorly in comparison with a full
integrated modulating boiler.


* elimination of boiler cycling when on part load, which gives far
greater
boiler longevity on all components.

It does not eliminate boiler cycling because the damned thing is being
switched on and off.


* oversized rads to cope with a condensing boiler giving lower return
temperatures.

If possible one should always do that with condensing boilers if
possible.

How is your system going to cope with heat output required for
different radiator design schemes? It is not monitoring the return
temperature.


* Variable speed pumps(s) on rad circuits.

Even better if one is integrated with the boiler and controlled by it.


* instant heat available first things in the mornings. Rads are fully
heated with afew minutes.

The same happens with a modulating boiler.

It is better if th control system can monitor the room temperature and
back off the heat supply at the right time.

If you dump heat from a store directly into radiators when it has been
a cold night and presumably the heatbank temperature is high, you are
going to get huge overshoot and waste of heat.

Now understand this if you can. It is not difficult. If there are parts
you are confused about, just accept it as right.

I am not and have never been confused.

Perhaps you would like to answer the questions that you have been
avoiding.

1/10 Very sad. A very poor score as you failed on all points. Now read
the post again and do a bit of thinking.

On Sun, 5 Sep 2004 12:49:56 +0100, "IMM" wrote:


"Andy Hall" wrote in message

Perhaps you would like to answer the questions that you have been
avoiding.

1/10 Very sad. A very poor score as you failed on all points. Now read
the post again and do a bit of thinking.


So, basically, in a completely predictable way, you can't come up with
a boiler for £400 or an external controller for your harebrain
scheme..... Not that it was worth doing in the first place.






..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Sun, 5 Sep 2004 12:49:56 +0100, "IMM" wrote:


"Andy Hall" wrote in message

Perhaps you would like to answer the questions that you have been
avoiding.

1/10 Very sad. A very poor score as you failed on all points. Now read
the post again and do a bit of thinking.


So, basically, in a completely predictable way, you can't come up with
a boiler for £400 or an external controller for your harebrain
scheme..... Not that it was worth doing in the first place.

Stop making things up. The scheme works with number in operation.

On Sat, 4 Sep 2004 21:53:07 +0100, "IMM" wrote:

It is. Even a modulating boiler cycles when demand is below the minimum kW.
With a heat bank, no cycling.
Hi,

How much heat is lost when a modulating condensing boiler cycles? Not
much I would have thought, as the heat exchanger probably has low
thermal mass and operates at a lower temperature.

Another way of doing it would be to connect the lower half of the heat
bank/thermal store in line with a differential bypass valve and 2 port
valve in parallel.

Then as the system gets up to temperature and the TRVs close, the
thermal store would take the excess heat. When that reaches
temperature and the burner switches off, the 2 port valve would open
to release the heat back into the system.

cheers,
Pete.

"Pete C" wrote in message
...
On Sat, 4 Sep 2004 21:53:07 +0100, "IMM" wrote:

It is. Even a modulating boiler cycles when demand is below the minimum
kW.
With a heat bank, no cycling.
Hi,

How much heat is lost when a modulating condensing boiler cycles? Not
much I would have thought, as the heat exchanger probably has low
thermal mass and operates at a lower temperature.

The controls can take a battering, raising the likelihood of breakdown.

Another way of doing it would be to
connect the lower half of the heat
bank/thermal store in line with a differential
bypass valve and 2 port
valve in parallel.

Then as the system gets up to temperature
and the TRVs close, the
thermal store would take the excess heat.
When that reaches
temperature and the burner switches
off, the 2 port valve would open
to release the heat back into the system.

I'm not sure if I'm with you. A buffer to take excess heat. Fine. Heat
from where? A better description of the pipe layout would be nice.

On Sun, 5 Sep 2004 22:17:29 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Sun, 5 Sep 2004 12:49:56 +0100, "IMM" wrote:


"Andy Hall" wrote in message

Perhaps you would like to answer the questions that you have been
avoiding.

1/10 Very sad. A very poor score as you failed on all points. Now read
the post again and do a bit of thinking.


So, basically, in a completely predictable way, you can't come up with
a boiler for £400 or an external controller for your harebrain
scheme..... Not that it was worth doing in the first place.

Stop making things up. The scheme works with number in operation.


I think that the boot is on the other foot here.

You are the one who introduced the notion of a simpl, cheap boiler.
Until then, the boiler under discussion was the WB modulating model
that I mentioned.

You then introduced the notion of an inappropriately applied weather
controller. The Danfoss Randall BEM5000 was mentioned but is not
really designed for your application, so goodness knows what it would
do. Presumably you would advocate splasjing out the money just to
find out....

So... Where is this £400 boiler and where is the controller to go with
it?


..andy

To email, substitute .nospam with .gl

On Sun, 05 Sep 2004 22:49:02 +0100, Pete C
wrote:

On Sat, 4 Sep 2004 21:53:07 +0100, "IMM" wrote:

It is. Even a modulating boiler cycles when demand is below the minimum kW.
With a heat bank, no cycling.
Hi,

How much heat is lost when a modulating condensing boiler cycles? Not
much I would have thought, as the heat exchanger probably has low
thermal mass and operates at a lower temperature.

Precisely - and it will be running at very low power anyway.



Another way of doing it would be to connect the lower half of the heat
bank/thermal store in line with a differential bypass valve and 2 port
valve in parallel.

Then as the system gets up to temperature and the TRVs close, the
thermal store would take the excess heat. When that reaches
temperature and the burner switches off, the 2 port valve would open
to release the heat back into the system.

The problem is that for DHW, the heatbank needs to have very different
characteristics.

If you segment the heatbank into two and deliberately run the lower
half at a lower operating temperature, you are cutting into the
storage for the DHW application. This implies either a larger or a
separate heatbank to do the job.

This is why it is far better to treat the CH and the DHW as the two
totally different systems that they are in terms of thermal
characteristics and time constants and to simply drive the radiators
from the modulating boiler. This is the intent of the manufacturer's
design and without a more sophisticated set of sensors and controller
than is inside the boiler, and a boiler that can be analogue
controlled, if the gas boiler is the only source of energy, you won't
improve on it.




cheers,
Pete.

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Sun, 5 Sep 2004 22:17:29 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Sun, 5 Sep 2004 12:49:56 +0100, "IMM" wrote:


"Andy Hall" wrote in message

Perhaps you would like to answer the questions that you have been
avoiding.

1/10 Very sad. A very poor score as you failed on all points. Now
read
the post again and do a bit of thinking.


So, basically, in a completely predictable way, you can't come up with
a boiler for £400 or an external controller for your harebrain
scheme..... Not that it was worth doing in the first place.

Stop making things up. The scheme works with number in operation.


I think that the boot is on the other foot here.

You are the one who introduced the notion of a simpl, cheap boiler.
Until then, the boiler under discussion was the WB modulating model
that I mentioned.

You then introduced the notion of an inappropriately applied weather
controller. The Danfoss Randall BEM5000 was mentioned but is not
really designed for your application, so goodness knows what it would
do. Presumably you would advocate splasjing out the money just to
find out....

So... Where is this £400 boiler and where is the controller to go with
it?

You mentioned £400 not me. You make thing up. I never introduced notions.
I introduced facts based on working models.

1/10 Very poor score.

"Andy Hall" wrote in message
...
On Sun, 05 Sep 2004 22:49:02 +0100, Pete C
wrote:

On Sat, 4 Sep 2004 21:53:07 +0100, "IMM" wrote:

It is. Even a modulating boiler cycles when demand is below the minimum
kW.
With a heat bank, no cycling.
Hi,

How much heat is lost when a modulating condensing boiler cycles? Not
much I would have thought, as the heat exchanger probably has low
thermal mass and operates at a lower temperature.

Precisely - and it will be running at very low power anyway.



Another way of doing it would be to connect the lower half of the heat
bank/thermal store in line with a differential bypass valve and 2 port
valve in parallel.

Then as the system gets up to temperature and the TRVs close, the
thermal store would take the excess heat. When that reaches
temperature and the burner switches off, the 2 port valve would open
to release the heat back into the system.

The problem is that for DHW, the heatbank needs to have very different
characteristics.

If you segment the heatbank into two and deliberately run the lower
half at a lower operating temperature, you are cutting into the
storage for the DHW application. This implies either a larger or a
separate heatbank to do the job.

A taller heat bank that's all.

This is why it is far better to treat the CH and the DHW as the two
totally different systems that they are in terms of thermal
characteristics and time constants and to simply drive the radiators
from the modulating boiler.

Not cheap to do this. and the boiler will cycle anyway. Better ways of
doing it.

This is the intent of the manufacturer's
design

The boiler manufacturers design you mean.

and without a more sophisticated set of sensors and controller
than is inside the boiler, and a boiler that can be analogue
controlled, if the gas boiler is the only source of energy, you won't
improve on it.

What tripe. Stop making things up.

On Mon, 6 Sep 2004 00:10:43 +0100, "IMM" wrote:




You mentioned £400 not me. You make thing up. I never introduced notions.
I introduced facts based on working models.


A WB Greenstar modulating boiler was introduced and priced at £725.

You then introduced the notion of an allegedly simpler and cheaper
solution using a simple boiler.

You described the solution and I costed it at just over £300 of
incremental components.

In order to come in at a lower cost, this gives you about £400 to
spend on a simple condensing boiler.

Which model is it and from where?

Alternatively, please list out your complete working model solution
with costings for each component.


..andy

To email, substitute .nospam with .gl

On Mon, 6 Sep 2004 00:14:08 +0100, "IMM" wrote:


"Andy Hall" wrote in message


If you segment the heatbank into two and deliberately run the lower
half at a lower operating temperature, you are cutting into the
storage for the DHW application. This implies either a larger or a
separate heatbank to do the job.

A taller heat bank that's all.

In order to achieve your solution, we are at a 300 litre minimum
heatbank.

From somebody who normally makes such a huge issue about airing
cupboard space as a justification for combis, this is hilarious.


This is why it is far better to treat the CH and the DHW as the two
totally different systems that they are in terms of thermal
characteristics and time constants and to simply drive the radiators
from the modulating boiler.

Not cheap to do this.

Of course it is. You simply need a system boiler and a diverter
valve.

When the boiler gets a signal from the DHW, it can wind up to full
power for the short suration required.

During CH operation, it will modulate down to the heat requirement
directly required by the radiators. A simple, efficient and
effective solution.



and the boiler will cycle anyway.

For a corner case around the lower modulting limit of the boiler.
Would you like mw to do the sums for you to show that this is a
non-issue.

Better ways of
doing it.

Not with a heatbank when a condensing boiler is the sole source of
energy.




This is the intent of the manufacturer's
design

The boiler manufacturers design you mean.

Of course. In the absence of a sophisticated external controller
with full instrumentation and analogue control of the boiler, having
the intelligence in the boiler is the obvious and correct place.


and without a more sophisticated set of sensors and controller
than is inside the boiler, and a boiler that can be analogue
controlled, if the gas boiler is the only source of energy, you won't
improve on it.

What tripe. Stop making things up.

Go and do some reading on control systems and condensing boiler
technology - none of these are complicated concepts for most people.


..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Mon, 6 Sep 2004 00:10:43 +0100, "IMM" wrote:




You mentioned £400 not me. You make thing up. I never introduced
notions.
I introduced facts based on working models.


A WB Greenstar modulating boiler was introduced and priced at £725.

You then introduced the notion of an allegedly simpler and cheaper
solution using a simple boiler.

You described the solution and I costed it at just over £300 of
incremental components.

In order to come in at a lower cost, this gives you about £400 to
spend on a simple condensing boiler.

Which model is it and from where?

A boiler with full load compensation modulating control within integral
weather compensator, the sort you keep going on about is well north of
£1000, more like £1,300-1,500. A £700 W-B appears super cheap in
comparison. Ideals are quite cheap. Other makes are well priced if you
look around. Halstead, BIASI, etc, etc. are all doing condensers and are
available a decent prices, that are well south of £1,500.

Alternatively, please list out your complete working model solution
with costings for each component.

Do you want my shoe size too?

"Andy Hall" wrote in message
...
On Mon, 6 Sep 2004 00:14:08 +0100, "IMM" wrote:


"Andy Hall" wrote in message


If you segment the heatbank into two and deliberately run the lower
half at a lower operating temperature, you are cutting into the
storage for the DHW application. This implies either a larger or a
separate heatbank to do the job.

A taller heat bank that's all.

In order to achieve your solution, we are at a 300 litre minimum
heatbank.

From somebody who normally
makes such a huge issue about airing
cupboard space as a justification for
combis, this is hilarious.

If you have a cylinder taking a foot higher is no big deal. It can always go
in the loft.

This is why it is far better to treat the CH and the DHW as the two
totally different systems that they are in terms of thermal
characteristics and time constants and to simply drive the radiators
from the modulating boiler.

Not cheap to do this.

Of course it is.

It isn't. When installing a heat bank you may as well take advantage of
what it can offer. A simple boiler and a weather compensator transforms it,
and very cheaply too.

What tripe. Stop making things up.

Go and do some reading on control
systems and condensing boiler
technology - none of these are
complicated concepts for most people.

Unfortunately you have only read about these. As you lack focus with a poor
attention span the results will be skewed.

On Mon, 6 Sep 2004 09:45:20 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Mon, 6 Sep 2004 00:10:43 +0100, "IMM" wrote:




You mentioned £400 not me. You make thing up. I never introduced
notions.
I introduced facts based on working models.


A WB Greenstar modulating boiler was introduced and priced at £725.

You then introduced the notion of an allegedly simpler and cheaper
solution using a simple boiler.

You described the solution and I costed it at just over £300 of
incremental components.

In order to come in at a lower cost, this gives you about £400 to
spend on a simple condensing boiler.

Which model is it and from where?

A boiler with full load compensation modulating control within integral
weather compensator, the sort you keep going on about is well north of
£1000, more like £1,300-1,500.

I am fully aware of that, but as you well know, it was not the
question.


A £700 W-B appears super cheap in
comparison. Ideals are quite cheap. Other makes are well priced if you
look around. Halstead, BIASI, etc, etc. are all doing condensers and are
available a decent prices, that are well south of £1,500.

I know, but where is your simple boiler at £400?



Alternatively, please list out your complete working model solution
with costings for each component.

Do you want my shoe size too?


Nope. Just the costings to justify your project.


..andy

To email, substitute .nospam with .gl

On Mon, 6 Sep 2004 09:50:38 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Mon, 6 Sep 2004 00:14:08 +0100, "IMM" wrote:


"Andy Hall" wrote in message


If you segment the heatbank into two and deliberately run the lower
half at a lower operating temperature, you are cutting into the
storage for the DHW application. This implies either a larger or a
separate heatbank to do the job.

A taller heat bank that's all.

In order to achieve your solution, we are at a 300 litre minimum
heatbank.

From somebody who normally
makes such a huge issue about airing
cupboard space as a justification for
combis, this is hilarious.

If you have a cylinder taking a foot higher is no big deal. It can always go
in the loft.


You know, I was always told that when you're in a hole, stop digging.

However.......

A 300 litre heatbank on a standard footprint will be approximately 2m
high and weigh over 300kg.

This is going to require a loft with this much headroom in a place
that will support this weight.

Of course you could always put the 200 litre one in the loft and the
100 litre DHW one in the airing cupboard I suppose.

Now what was the point about space in houses being precious?



This is why it is far better to treat the CH and the DHW as the two
totally different systems that they are in terms of thermal
characteristics and time constants and to simply drive the radiators
from the modulating boiler.

Not cheap to do this.

Of course it is.

It isn't. When installing a heat bank you may as well take advantage of
what it can offer. A simple boiler and a weather compensator transforms it,
and very cheaply too.

So is this a large combined heatbank, two smaller ones or ...??

Please give model numbers and prices for the simple boiler and the
weather compensator.




What tripe. Stop making things up.

Go and do some reading on control
systems and condensing boiler
technology - none of these are
complicated concepts for most people.

Unfortunately you have only read about these. As you lack focus with a poor
attention span the results will be skewed.

Oh I see.

Now who is it that meanders around adding bits as they go and being
able to stick to and answer the questions on prices and models for the
components for their scheme?

Did you say that you were a plumber or a heating engineer?


..andy

To email, substitute .nospam with .gl

"IMM" wrote in message ...
"Andy Hall" wrote in message
...
On Wed, 1 Sep 2004 17:58:59 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Wed, 1 Sep 2004 15:47:49 +0100, "IMM" wrote:


"Andy Hall" wrote in message

Also making the primary pressurised
with a direct heatbank (i.e. the
bulk contents of the cylinder are pressurised)
means that for Building
Regulations section G purposes it counts as a
sealed storage system and must therefore be
installed by a certified installer.

These are available, but rare and termed directly pressurised.

I wanted to make the point because there are direct heatbanks on
the
market and it is not always immediately obvious that they are not
suitable for pressurised primary operation.

They are suitable.

From the DPS site:

"GX units are only suitable for a vented boiler / heating systems with
a Feed & Expansion Tank."

You were on about the whole cylinder and primary circuit being
pressurised.

Exactly, and this one is not suitable for that.

So?

Having the primary vented, whether with an integral F&E tank or
not
means that this can be a DIY job, although is still subject to a
Building Notice because of part L1.

However, some boilers will not accept
having an open vented primary,

Few and far between.

I've got one.

You have not got a heat bank.

That's not the point.

You have NOT Got a heat bank.!

That's irrelevant. You haven't got a hundred acres.

It does not change the fact that you haven't got a heat bank and you say you
have and say because you actually haven't it doesn't matter. You need
therapy

There are boilers around that are designed for
sealed system use. Vaillant ecoMAX is one example in addition to the
Micromat that I have,Viessmann is another.

You are confused.

I'm seldom confused and certainly not here.

Imagine your post on ripped paper and written in crayon and the scene is
set.

LOL!