Hello all,

Just though I'd call in here to run this one past the more experienced...

I currently have a gravity fed hot water system. I'm about to build a small
extension and will replace the current boiler while doing so. I have
pondered for a while the idea of a mains pressure hot water system but am
really concerned about the lack of pressure at the upstairs shower. I
currently have a pressure pump installed and the shower is brilliant. I also
like the idea of a combi simply because of the fact that I'll never "run
out" of hot water.

Anyway, after reading loads of stuff on the web I have concluded (maybe
wrongly!!) that I should have a combi to feed everything but the showers and
retain the current hot water cylinder and pump just for the showers. I'd
obviously have to somehow plumb in the system to heat the water cylinder and
that will no doubt necessitate the use of motorised valves etc. I realise
that I'll still need to keep the loft tanks but don't mind that. I'll also
have two hot water supplies in case one fails and stored water in the loft
is always handy should there be a mains supply problem.

So, am I thinking right? and is there any where on the web where I can
source a plumbing & wiring diagram for this type of set up? I can plumb and
wire but haven't a clue where to start on this. I'll obviously need the
boiler to be on call for the central heating and the hot water and these
need to be independent.

Any other idea's appreciated too.

I have pondered for a while the idea of a mains pressure hot water system
but am really concerned about the lack of pressure at the upstairs shower.

Assuming that the mains pressure and flow is good, I'd do it the other way
round. Have the shower (and possibly kitchen tap) off the combi, and run the
bath from the cylinder, possibly using the pump.

Of course, you shouldn't rule out a mains pressure storage system which
gives the best of both worlds. I've just collected such a system this
morning, a 180l DPS Pandora. I'll let everyone know if it works once it is
finally connected up.

I'll obviously need the boiler to be on call for the central heating
and the hot water and these need to be independent.

You wire and plumb it just like you would a conventional heating system. You
will have to discard any boiler built in programmer, as it will only have
one channel. Either lose it, or set it to 24/7.

Decide on either Honeywell 'Y' or 'S' plan. Wire up in the conventional
fashion and lash up the final call for heat to the room thermostat
connection on the boiler. You'll probably need a volt free contact at the
end, so choose a programmer that has volt free contacts, as otherwise,
you'll need a relay, unless the boiler can accept a 230V call for heat.

Christian.

Christian McArdle wrote:

I have pondered for a while the idea of a mains pressure hot water system
but am really concerned about the lack of pressure at the upstairs shower.


Assuming that the mains pressure and flow is good, I'd do it the other way
round. Have the shower (and possibly kitchen tap) off the combi, and run the
bath from the cylinder, possibly using the pump.

Of course, you shouldn't rule out a mains pressure storage system which
gives the best of both worlds. I've just collected such a system this
morning, a 180l DPS Pandora. I'll let everyone know if it works once it is
finally connected up.


I've got one. Shoehorned the HW tank into the loft. Saves a lot of
space. Plumbing is more intricate - lots of safety pipes to dump
pressure outside etc, but overall performance is better than anything
else. Combis have pressure, but no flow rate IMHO, unless you go for a
really BIG one. Combis need to have heating capacity for peak hot water
flow. Mains pressure tank? You have three or four baths worth on tap all
teh time. Boiler needn't be as big.

I'd only use a combi on a strict budget, or in a small house with no
room for a HW tank.

I'd never use a gravity fed header tank unless teh local water supply
was known to be highly unreliable.

Here, water is 100% reliable, but electricity is not. No sparks means no
boiler. But HW tank is good for several baths, aga needs no psarks to
cook, and open fires take cxare of heating, and candles just about sort
out lighting. And battery radio allows local news coverage of 'national
electrical crisis'

AND I can recharge its batteris from the car.

I've just collected such a system this morning, a 180l DPS Pandora.

I've got one. Shoehorned the HW tank into the loft. Saves a lot of
space. Plumbing is more intricate - lots of safety pipes to dump
pressure outside etc,

The DPS Pandora is different from your system, though. Lower maximum flow
rates and won't work at all without electricity. However, it doesn't require
lots of safety pipes to dump pressure, which is the main reason I bought it.

Christian.

"Christian McArdle" wrote in message
et...
I've just collected such a system this morning, a 180l DPS Pandora.

I've got one. Shoehorned the HW tank into the loft. Saves a lot of
space. Plumbing is more intricate - lots of safety pipes to dump
pressure outside etc,

The DPS Pandora is different from your system,
though. Lower maximum flow rates

That can be sorted by installing another plate heat exchangers in parallel.
That's if you need very high flow rates of course.

and won't work at all without electricity. However, it doesn't require
lots of safety pipes to dump pressure,

Or an overflow pipe either, so can be fitted in the centre of a house, like
under the stairs , right out of the way. Large metals pipes penetrating
walls can be a large heat sink.

which is the main reason I bought it.




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At the risk of starting WW3.5, is it possible to add a mains storage system
to an existing (Bosch Worcester Greenstar) combi?

And if so any recomendations?

TIA

Bax


"Christian McArdle" wrote in message
et...
I have pondered for a while the idea of a mains pressure hot water system
but am really concerned about the lack of pressure at the upstairs
shower.

Assuming that the mains pressure and flow is good, I'd do it the other way
round. Have the shower (and possibly kitchen tap) off the combi, and run
the
bath from the cylinder, possibly using the pump.

Of course, you shouldn't rule out a mains pressure storage system which
gives the best of both worlds. I've just collected such a system this
morning, a 180l DPS Pandora. I'll let everyone know if it works once it is
finally connected up.

I'll obviously need the boiler to be on call for the central heating
and the hot water and these need to be independent.

You wire and plumb it just like you would a conventional heating system.
You
will have to discard any boiler built in programmer, as it will only have
one channel. Either lose it, or set it to 24/7.

Decide on either Honeywell 'Y' or 'S' plan. Wire up in the conventional
fashion and lash up the final call for heat to the room thermostat
connection on the boiler. You'll probably need a volt free contact at the
end, so choose a programmer that has volt free contacts, as otherwise,
you'll need a relay, unless the boiler can accept a 230V call for heat.

Christian.

"Baxter Basics" wrote in message
et...

At the risk of starting WW3.5, is it possible to add a mains storage
system
to an existing (Bosch Worcester Greenstar) combi?

Yes.

And if so any recomendations?

The Pandora, as below.

"Christian McArdle" wrote in message
et...
I have pondered for a while the idea of a mains pressure hot water
system
but am really concerned about the lack of pressure at the upstairs
shower.

Assuming that the mains pressure and flow is good, I'd do it the other
way
round. Have the shower (and possibly kitchen tap) off the combi, and run
the
bath from the cylinder, possibly using the pump.

Of course, you shouldn't rule out a mains pressure storage system which
gives the best of both worlds. I've just collected such a system this
morning, a 180l DPS Pandora. I'll let everyone know if it works once it
is
finally connected up.

I'll obviously need the boiler to be on call for the central heating
and the hot water and these need to be independent.

You wire and plumb it just like you would a conventional heating system.
You
will have to discard any boiler built in programmer, as it will only
have
one channel. Either lose it, or set it to 24/7.

Decide on either Honeywell 'Y' or 'S' plan. Wire up in the conventional
fashion and lash up the final call for heat to the room thermostat
connection on the boiler. You'll probably need a volt free contact at
the
end, so choose a programmer that has volt free contacts, as otherwise,
you'll need a relay, unless the boiler can accept a 230V call for heat.

Christian.






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Assuming that the mains pressure and flow is good, I'd do it the other way
round. Have the shower (and possibly kitchen tap) off the combi, and run
the
bath from the cylinder, possibly using the pump.

Eh?!

Assuming that the mains pressure and flow is good, I'd do it the other
way
round. Have the shower (and possibly kitchen tap) off the combi, and run
the
bath from the cylinder, possibly using the pump.

Eh?!

Showers need pressure as much as they need flow. This means that an
excellent shower can be obtained by a combi, which uses mains pressure but
is limited in flow rate. It will also be less noisy, as no pump is needed.

The cylinder is capable of supplying much higher flow rates. However,
gravity feed might not be able to get sufficient flow rate at the taps, for
which a pump can be beneficial.

Christian.

At the risk of starting WW3.5, is it possible to add a mains storage
system
to an existing (Bosch Worcester Greenstar) combi?

Yes. You can add anything to a combi that could be added to a conventional
boiler. A combi is just a conventional boiler with an additional
instantaneous hot water heat exchanger and associated controls.

You'll need a pile of extra controls, programmers and valves, as would be
required for a heating system using a conventional boiler. These are
frequently packaged into convenient kits with substantial discounts.

And if so any recomendations?

There are two main contenders. Both are similar in purchase cost. Both
vastly superior to a combi boiler in performance, assuming your mains can
supply the water.

a) An unvented hot water cylinder. This provides the ultimate flow rate,
assuming your mains can supply it. It requires extra safety controls, which
mean that you need a specific safety inspection for building regulations or
a specifically qualified installer. Example: Heatrae Sadia Megaflo.

b) A heat bank (or thermal store, which is similar). This provides good flow
rates (again assuming good mains supply), but not as good as the unvented
cylinder. It is inherently safer as the hot water storage itself is at
atmospheric pressure, so is not subject to potentially dangerous pressure
rises when heated. This makes is much easier to install. Example: DPS
Pandora (also available with complete CH+DHW 'Y' or 'S' plan system controls
and 2 channel programmer ready mounted to the cylinder).

I've just bought a DPS Pandora, but it won't be connected for a week or two.
It looks the part, though. We've managed to hoist it into the loft, where
there is no convenient overflow or pressure relief outlet due to a planned
dormer extension.

Christian.

Christian, do the manufacturers of the Pandora have a web presence?

TIA

Bax


"Christian McArdle" wrote in message
et...
I have pondered for a while the idea of a mains pressure hot water system
but am really concerned about the lack of pressure at the upstairs
shower.

Assuming that the mains pressure and flow is good, I'd do it the other way
round. Have the shower (and possibly kitchen tap) off the combi, and run
the
bath from the cylinder, possibly using the pump.

Of course, you shouldn't rule out a mains pressure storage system which
gives the best of both worlds. I've just collected such a system this
morning, a 180l DPS Pandora. I'll let everyone know if it works once it is
finally connected up.

I'll obviously need the boiler to be on call for the central heating
and the hot water and these need to be independent.

You wire and plumb it just like you would a conventional heating system.
You
will have to discard any boiler built in programmer, as it will only have
one channel. Either lose it, or set it to 24/7.

Decide on either Honeywell 'Y' or 'S' plan. Wire up in the conventional
fashion and lash up the final call for heat to the room thermostat
connection on the boiler. You'll probably need a volt free contact at the
end, so choose a programmer that has volt free contacts, as otherwise,
you'll need a relay, unless the boiler can accept a 230V call for heat.

Christian.

Christian, do the manufacturers of the Pandora have a web presence?

www.heatweb.com

The website isn't quite up to date. AFAICT, the "2002" specification
heatbanks have been replaced with "5670" specification types referred to as
Pandoras (which are mentioned). However, the general principles and
specifications are similar and (I'm told) prices reduced. The prices aren't
listed on the website, but are very similar to equivalent Megaflos as listed
by discountedheating.com if you want some idea.

The company is of the a small friendly variety. This means that lead times
aren't that great (it isn't off the shelf at a plumber's merchant like a
Megaflo), but they are able to build the things to a precise specification,
if a standard model isn't quite right.

Christian.

"Christian McArdle" wrote in message
et...
Assuming that the mains pressure and flow is good, I'd do it the other
way
round. Have the shower (and possibly kitchen tap) off the combi, and
run
the
bath from the cylinder, possibly using the pump.

Eh?!

Showers need pressure as much as they need flow. This means that an
excellent shower can be obtained by a combi, which uses mains pressure but
is limited in flow rate. It will also be less noisy, as no pump is needed.

The cylinder is capable of supplying much higher flow rates. However,
gravity feed might not be able to get sufficient flow rate at the taps,
for
which a pump can be beneficial.

You obviously mean just for a shower as a tank fed bath can supply very high
flow rates, but poor pressure.


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You obviously mean just for a shower as a tank fed bath can supply very
high
flow rates, but poor pressure.

That would depend on the pipe diameter and routing. Most gravity fed baths
I've used have had substandard flow rates, sometimes not much more than a
combi boiler. A pump is often quite an improvement. The problems occur when
the hot water cylinder is tucked away somewhere quite different from the
location of the bath and the cold water tank, leading to convoluted pipe
runs, sometimes even run in 15mm pipe. It is these situations that a pump is
often quite an improvement as far as baths are concerned. With showers, you
usually need a pump to improve the pressure so that the water can squeeze
through the holes.

Christian.

Christian McArdle wrote:

You obviously mean just for a shower as a tank fed bath can supply very

high

flow rates, but poor pressure.


That would depend on the pipe diameter and routing. Most gravity fed baths
I've used have had substandard flow rates, sometimes not much more than a
combi boiler. A pump is often quite an improvement. The problems occur when
the hot water cylinder is tucked away somewhere quite different from the
location of the bath and the cold water tank, leading to convoluted pipe
runs, sometimes even run in 15mm pipe. It is these situations that a pump is
often quite an improvement as far as baths are concerned. With showers, you
usually need a pump to improve the pressure so that the water can squeeze
through the holes.

Christian.




Thats right. One of the thngs they teach you at a snotty UNI is that
flow rate is a function of both pressure and bore diameter, and indeed
bore length..

I guess where IMM went they didn't even explain what 'function of' means
in the mathematical sense...its a bit beyond the Boys Bumper Book of How
Things Work.

"The Natural Philosopher" wrote in message
...
Christian McArdle wrote:

You obviously mean just for a shower as a tank fed bath can supply very

high

flow rates, but poor pressure.


That would depend on the pipe diameter and routing. Most gravity fed
baths
I've used have had substandard flow rates, sometimes not much more than
a
combi boiler. A pump is often quite an improvement. The problems occur
when
the hot water cylinder is tucked away somewhere quite different from the
location of the bath and the cold water tank, leading to convoluted pipe
runs, sometimes even run in 15mm pipe. It is these situations that a
pump is
often quite an improvement as far as baths are concerned. With showers,
you
usually need a pump to improve the pressure so that the water can
squeeze
through the holes.

Christian.




Thats right. One of the thngs they teach you at a snotty UNI is that
flow rate is a function of both pressure and bore diameter, and indeed
bore length..

I guess where IMM went they didn't even explain what 'function of' means
in the mathematical sense...its a bit beyond the Boys Bumper Book of How
Things Work.

You really don't know, do you?


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"Christian McArdle" wrote in message
et...
You obviously mean just for a shower as a tank fed bath can supply very
high
flow rates, but poor pressure.

That would depend on the pipe diameter and routing. Most gravity fed baths
I've used have had substandard flow rates, sometimes not much more than a
combi boiler. A pump is often quite an improvement. The problems occur
when
the hot water cylinder is tucked away somewhere quite different from the
location of the bath and the cold water tank, leading to convoluted pipe
runs, sometimes even run in 15mm pipe. It is these situations that a pump
is
often quite an improvement as far as baths are concerned. With showers,
you
usually need a pump to improve the pressure so that the water can squeeze
through the holes.

Most gravity systems are fitted with 22mm pipe and lately the cold feed to
the cylinder in 28mm. The really do flow.


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"Christian McArdle" wrote in message
et...
Christian, do the manufacturers of the Pandora have a web presence?

www.heatweb.com

What is your spec? Does it have a blending valve on the flow and return?


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What is your spec? Does it have a blending valve on the flow and return?

No blending valve. The indirect coil comes unadorned. There is a
thermostatic mixing valve on the DHW outlet, though.

I'm certainly interested in anything that can reduce the return temperature,
though. I wouldn't mind reducing the radiator flow temperature, too, for
safety reasons. I have a five year old, whose bed is adjacent to a radiator.
Can blending valves achieve this?

Christian.

On Wed, 1 Oct 2003 09:18:20 +0100, "Christian McArdle"
wrote:

What is your spec? Does it have a blending valve on the flow and return?

No blending valve. The indirect coil comes unadorned. There is a
thermostatic mixing valve on the DHW outlet, though.

I'm certainly interested in anything that can reduce the return temperature,
though. I wouldn't mind reducing the radiator flow temperature, too, for
safety reasons. I have a five year old, whose bed is adjacent to a radiator.
Can blending valves achieve this?

Christian.


Are you running the radiators from the store as well, Christian?

Otherwise, if it's a condensing boiler, does it have separate
temperatures of operation when in DHW mode vs. CH?

On mine, there are zone valves on the feed from the boiler - there
being one quite close to it for a new radiator. There is then the
original 22mm feed to the airing cupboard where there is one zone
valve for CH and one for the cylinder.

When the CH demands, the valves for that open and the flow is limited
to 70 degrees. When the cylinder demands, these valves close and
the DHW one opens. Then the boiler will run at 82 or even 85 degrees
flow.

If your boiler doesn't do this but modulates based on the return
temperature, then adding a blending valve to the radiator circuit to
feed some water back to the return, the effect would be to reduce the
heat output because the boiler will see it as reduced load.

Then you have to think about whether the radiator sizes are adequate
at the reduced temperature to give the heat output you need.


..andy

To email, substitute .nospam with .gl

Are you running the radiators from the store as well, Christian?

No.

Otherwise, if it's a condensing boiler, does it have separate
temperatures of operation when in DHW mode vs. CH?

The boiler is a Worcester-Bosch Greenstar HE System. Does this have the
ability to have call for heat signals at different nominal flow
temperatures?

The system will be a Honeywell 'S' plan. Initially, it will have 3 zones,
upstairs, downstairs and water heating. This will ultimately be expanded to
5 zones, for the loft conversion and conservatory. As planned, there is no
hot water priority. Although I could possibly contrive such a system, it
might require relays or similar to disable the heating circuits when the
water valve is open. I'd prefer to avoid this, unless it will significantly
improve performance.

Then you have to think about whether the radiator sizes are adequate
at the reduced temperature to give the heat output you need.

Probably. I can turn the blending valve up in cold weather. If I install a
blending valve, do I need an additional pump on the heating circuits?

Christian.

As planned, there is no hot water priority.

I suppose I could implement priority simply using a 3 way diverter valve and
then subdividing the heating port later on. I don't know if Honeywell have a
letter for this type of system. Although I've already got the three 2 port
valves, I'll have needed a couple more later on anyway, so the one freed up
won't be wasted.

Christian.

"Christian McArdle" wrote in message
et...
What is your spec? Does it have a blending valve on the flow and return?

No blending valve. The indirect coil comes unadorned. There is a
thermostatic mixing valve on the DHW outlet, though.

I'm certainly interested in anything that can reduce the return
temperature,
though. I wouldn't mind reducing the radiator flow temperature, too, for
safety reasons. I have a five year old, whose bed is adjacent to a
radiator.
Can blending valves achieve this?

Christian.

This is a DHW only heat bank. So you will be having a diverter valve for
either CH & DHW, with the CH running directly from the condensing boiler. A
condensing boiler with load compensation control will reduce the rad temps
for the vast majority of operation, except on warm up in winter which will
be rather high. You can have a high temp limit on some boilers, so no over
hot rad temps.

A blending valve can reduce max rad temps, but there is other ways of doing
it. What you want is the boiler at full temp when DHW is being called and
then a lower temp for the CH mode. In a simple boiler this is achieved by
having the boiler stat on full, and a pipe thermostat on the boiler flow.
When calling for DHW the pipe stat is switched out, when CH is called it is
switched in. Very simple, and very effective.

To keep the return temps cool you could have:

1. Oversized rads
2. Install a plate heat exchangers on the return to the boiler with the
cold water mains entering this first. It will act a pre-warmer when the
boiler is operational either for DHW or CH and hot water is being drawn off.
It will also reduce the return temp into the boiler. It will also impove
the flow rate when the boiler is operational. You could have the control
system so that the boioer always fires on DHW when water is drawn-off, as a
combi does. Plate heat exchangers are not that expensive.

What make & model of cylinder thermostat is DPS using on the Pandora heat
bank?
What kW rating is the coil?



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"Christian McArdle" wrote in message
et...
As planned, there is no hot water priority.

I suppose I could implement priority simply using a 3 way diverter valve
and
then subdividing the heating port later on. I don't know if Honeywell have
a
letter for this type of system. Although I've already got the three 2 port
valves, I'll have needed a couple more later on anyway, so the one freed
up
won't be wasted.

Christian.

Drayton do a 3-port diverter valve with an end switch using the normal
syncron motor. Most do not have the end switch. Also the mid-position
Honeywell can have a 2-port actuator fitted to convert it to a diverter.
May be a little too expensive for you to buy two valves, but easy enough to
convert a system from mid-position to priority diverter. But it may have
been better for you to buy the Y plan and convert.



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On Wed, 1 Oct 2003 11:47:12 +0100, "Christian McArdle"
wrote:

Are you running the radiators from the store as well, Christian?

No.

Otherwise, if it's a condensing boiler, does it have separate
temperatures of operation when in DHW mode vs. CH?

The boiler is a Worcester-Bosch Greenstar HE System. Does this have the
ability to have call for heat signals at different nominal flow
temperatures?

The system will be a Honeywell 'S' plan. Initially, it will have 3 zones,
upstairs, downstairs and water heating. This will ultimately be expanded to
5 zones, for the loft conversion and conservatory. As planned, there is no
hot water priority. Although I could possibly contrive such a system, it
might require relays or similar to disable the heating circuits when the
water valve is open. I'd prefer to avoid this, unless it will significantly
improve performance.

Then you have to think about whether the radiator sizes are adequate
at the reduced temperature to give the heat output you need.

Probably. I can turn the blending valve up in cold weather. If I install a
blending valve, do I need an additional pump on the heating circuits?

Christian.


OK.

I am not sure about this boiler - it was not one that I looked at when
I was searching.

I wonder whether otherwise you could alter the behaviour of the boiler
by arranging a zone valve and bypass in effect across the flow and
return of the CH circuits - i.e. to open when any of the CH zone
valves open.

..andy

To email, substitute .nospam with .gl

This is a DHW only heat bank. So you will be having a diverter valve for
either CH & DHW, with the CH running directly from the condensing boiler.

My original intention was to use no diverter valve, just 2 ports on every
circuit. Now, I'm not so sure. I may install a diverter valve for the hot
water and use 2 port valves for the heating sub circuits.

What kW rating is the coil?

I don't know. However, the cylinder appears to be made by Telford, so I
might have a look to see what their standard coils are rated at. I suspect
it will be less than the boiler's maximum output, hence why I wasn't too
concerned about priority operation.

Christian.

I wonder whether otherwise you could alter the behaviour of the boiler
by arranging a zone valve and bypass in effect across the flow and
return of the CH circuits - i.e. to open when any of the CH zone
valves open.

Not quite sure I get you. Do you mean mix some flow water into the return so
fooling the boiler to modulate down?

To be honest, I'm surprised boiler manufacturers don't have facilities to
control the flow temperature programmatically. It seems a common
requirement, particularly for underfloor heating and now that condensing
technology promotes lower radiator temperatures (but still requires nice hot
water in the cylinder).

Christian.

"Christian McArdle" wrote in message
et...
This is a DHW only heat bank. So you will be having a diverter valve for
either CH & DHW, with the CH running directly from the condensing boiler.

My original intention was to use no diverter valve, just 2 ports on every
circuit. Now, I'm not so sure. I may install a diverter valve for the hot
water and use 2 port valves for the heating sub circuits.

What kW rating is the coil?

I don't know. However, the cylinder appears to be made by Telford, so I
might have a look to see what their standard coils are rated at. I suspect
it will be less than the boiler's maximum output, hence why I wasn't too
concerned about priority operation.

Coil areas:

80 litre Telford Typhoon cylinder has: 1.2 squ metres coil surface area.
120 litre Telford Typhoon cylinder has: 1.55 squ metres coil surface area.
Calculated to give 12-16 minutes recovery time.

125 litre Tornado unvented cylinder has: 0.704 squ. metres coil surface
area.



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120 litre Telford Typhoon cylinder has: 1.55 squ metres coil surface area.
Calculated to give 12-16 minutes recovery time.

It is a 180L, so it couldn't be a Typhoon. I'll need to examine further to
see what it might be. It could just be a standard indirect cylinder, or a
special order item for them.

Christian.

"Christian McArdle" wrote in message
et...
120 litre Telford Typhoon cylinder has: 1.55 squ metres coil surface
area.
Calculated to give 12-16 minutes recovery time.

It is a 180L, so it couldn't be a Typhoon. I'll need to examine further to
see what it might be. It could just be a standard indirect cylinder, or a
special order item for them.

It probably uses standard coil sizes, so the next one up from the 120 it may
be. I can't see DPS using a Part L coil.



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It probably uses standard coil sizes, so the next one up from the 120
it may be. I can't see DPS using a Part L coil.

They say they use coils in excess of that required by the British Standard,
which is pretty meaningless really. TBH, I don't really care. I'm sure it
should be well overspecced for my storage needs. I'm pretty close to running
two baths simultaneously with a 180L with no regeneration at all. I'm going
to be running the hot water circuit 24/7. I've never run out of hot water
with a 120L gravity indirect cylinder, so I'm not planning to start now.

Christian.

On Wed, 1 Oct 2003 13:53:50 +0100, "Christian McArdle"
wrote:

I wonder whether otherwise you could alter the behaviour of the boiler
by arranging a zone valve and bypass in effect across the flow and
return of the CH circuits - i.e. to open when any of the CH zone
valves open.

Not quite sure I get you. Do you mean mix some flow water into the return so
fooling the boiler to modulate down?

Exactly. If you think about it in terms of an electrical circuit,
it becomes clear.


To be honest, I'm surprised boiler manufacturers don't have facilities to
control the flow temperature programmatically. It seems a common
requirement, particularly for underfloor heating and now that condensing
technology promotes lower radiator temperatures (but still requires nice hot
water in the cylinder).


I know. It would make sense, wouldn't it.

At this point, heat banks are not that common, but the idea of being
able to transfer maximum energy into even a conventional cylinder via
coil so that the boiler is off line with respect to the CH for the
minimum time is pretty obvious and a common scenario.

The CH might have a max allowed temp. of 82 degrees if you are
replacing an old boiler and not the radiators - it will still modulate
down when the weather is warm enough not to need full output (and this
is virtually all the time); 70 degrees if you increased radiator
capacity so that there is enough heat output even when it's very cold
and as you say UFH with max temperature of 50 degrees.
Since there are cases where at least two of these might be in use plus
DHW, controllers should really be more flexible. After all, with a
decent controller, essentially firmware based, there is zero
incremental cost to do this.

I suspect that the reason it isn't widely done is because the average
installer is conservative anyway and often does not make three digits
regarding IQ.




Christian.


..andy

To email, substitute .nospam with .gl

"Christian McArdle" wrote in message
et...
Christian, do the manufacturers of the Pandora have a web presence?

www.heatweb.com

The website isn't quite up to date. AFAICT, the "2002" specification
heatbanks have been replaced with "5670" specification types referred to
as
Pandoras (which are mentioned). However, the general principles and
specifications are similar

Christian,

Who sized your 180 litre heat bank?


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"Christian McArdle" wrote in message
et...
120 litre Telford Typhoon cylinder has: 1.55 squ metres coil surface
area.
Calculated to give 12-16 minutes recovery time.

It is a 180L, so it couldn't be a Typhoon. I'll need to examine further to
see what it might be. It could just be a standard indirect cylinder, or a
special order item for them.

Christian,

You should be able to see the coil inside the cylinder through the
immersion, or other, tappings. The quick recovery coil has about 4 soft
copper coils.


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Who sized your 180 litre heat bank?

Me, supported by the simple table on their website and a quick chat with
their sales director. It is based on having a bath and a shower
simultaneously.

Christian.

"Christian McArdle" wrote in message
t...
Who sized your 180 litre heat bank?

Me, supported by the simple table on their website and a quick chat with
their sales director. It is based on having a bath and a shower
simultaneously.

Christian,

A 140-150 will do a bath. Arrange the system so that the boilers output is
combined with the heat banks and a greater flowrate with a smaller cylinder
and then the cylinder is exhausted it will revert to the boilers output,
which in your case will give around 10 litres/min.





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Arrange the system so that the boilers output is combined with the heat
banks and a greater flowrate with a smaller cylinder

It is an indirect coil, so it won't have this ability. It needed to be
indirect, because I needed a pressurised sealed CH circuit, which obviously
isn't possible with a direct cylinder with atmospheric pressure water.

It is sized so I don't need to rely on recovery for it to work. The sizes
only affect the height of the cylinder, so there is no space implication in
going for a 180L instead of a 150L or a 120L. It's going in the loft.

Christian.

In article , cmcardle75
@nospam.yahooxxxx.co.uk says...
Who sized your 180 litre heat bank?

Me, supported by the simple table on their website and a quick chat with
their sales director. It is based on having a bath and a shower
simultaneously.

You take your personal hygene seriously! :-)

--
http://www.beluga.freeserve.co.uk

"Christian McArdle" wrote in message
t...

Arrange the system so that the boilers
output is combined with the heat
banks and a greater flowrate with a
smaller cylinder

It is an indirect coil, so it won't have this
ability. It needed to be indirect, because
I needed a pressurised sealed CH circuit,
which obviously isn't possible with a direct
cylinder with atmospheric pressure water.

That doesn't make any difference. Put a 3-way diverter valve on the flow
from the boiler to the coil of the cylinder, and take a pipe from one port
to another plate heat exchanger. Have the cold water coming into the
boilers plate and then out into the heat banks plate.

The outputs are combined. The heat bank assists the boilers output, which
will be at full belt. This way the stored water is kept long. When the
heat bank runs out of hot water an electronic quick acting pipe stat with an
insert pocket will cut out the heat banks plate heat exchanger pump
preventing the cool heat bank water cooling the boiler heated water, then
only the boiler will provide DHW, meaning you can never run out of DHW
whatsoever. When there is no flow the boiler immediately starts to re-heat
the heat bank. The boiler should be full on and the heat bank will top up
the shortfall. This way you will get around an extra 10-11 litres per
minute of flowrate, never run out of hot water and a smaller cylinder can be
used.

There is also backup in case the heat banks DHW pump fails. All for the cost
of a plate heat exchanger, pipe stat and a 3-way valve. You have to arrange
the control system of course.

BTW, did DPS leave the CH tappings on the heat bank?

It is sized so I don't need to rely on
recovery for it to work. The sizes
only affect the height of the cylinder,
so there is no space implication in
going for a 180L instead of a 150L or
a 120L. It's going in the loft.




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Me, supported by the simple table on their website and a quick chat with
their sales director. It is based on having a bath and a shower
simultaneously.

You take your personal hygene seriously! :-)

Oh yes. It's a great way of washing your hair. ;-)

Christian.