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  #1   Report Post  
Mungo \two sheds\ Toadfoot
 
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Default Central heating Q

Hi peeps,

The thermostat that controls our central heating boiler is in the,
fairly small, hallway. Is this the best place for it?

If our living room and kitchen doors are closed and someone opens the front
door won't the stat think the house is freezing and fire up the heating? If
the stat's trying to get the hallway up to, say, 28 degrees, wouldn't the
rads in other parts of the house be getting hotter than they needed to?

Our last house had the stat in the living room, which sounds a much better
idea to me - if the main room is warm then the rest of the house is too,
surely?

Also, I'm thinking of putting TRVs on all the rads so that the bedroom rads
can be turned down in the daytime. I'm guessing that they can just be
swapped with the existing valves (after draining down of course)?

If I did this would it mean that I could leave the stat where it was? It'd
be a right pig to move and I'd rather not!

Any problems with this, or advice?

Ta,

Si


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Brian Reay
 
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Default Central heating Q

"Mungo "two sheds" Toadfoot" wrote in
message ...
Hi peeps,

The thermostat that controls our central heating boiler is in the,
fairly small, hallway. Is this the best place for it?

If our living room and kitchen doors are closed and someone opens the

front
door won't the stat think the house is freezing and fire up the heating?

If
the stat's trying to get the hallway up to, say, 28 degrees, wouldn't the
rads in other parts of the house be getting hotter than they needed to?

Our last house had the stat in the living room, which sounds a much better
idea to me - if the main room is warm then the rest of the house is too,
surely?

Also, I'm thinking of putting TRVs on all the rads so that the bedroom

rads
can be turned down in the daytime. I'm guessing that they can just be
swapped with the existing valves (after draining down of course)?

If I did this would it mean that I could leave the stat where it was? It'd
be a right pig to move and I'd rather not!


If the thermostat is in the living room and you have a gas fire- even for
'looks' - then the living room can be as warm as toast and the rest of the
house freezing.

In the hall, with a properly balanced system, you should be able to get a
acceptable temperature in the other rooms. If you them turn on the gas fire
in the living room (for that warm look or a roll in front of the fire with
the Mrs) you don't confuse the system.

Opening the front door etc will cause a 'burst' of the heating but that
inrush of could air will need warming or it can give cold draughts in the
other rooms.

On balance, I favour the thermostat in the hall.

Also, do a good job of draught excluding- that does wonders for the warm
'feel' of the house.

Regards

Brian
--
73
Brian
G8OSN
www.g8osn.org.uk
www.qsl.net/g8osn for FREE training material for the UK Foundation and
Intermediate Licences
www.phoenixradioclub.org.uk - a RADIO club specifically for those wishing
to learn more about amateur radio


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Mungo \two sheds\ Toadfoot
 
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Default Central heating Q


"Brian Reay" wrote in message
...

If the thermostat is in the living room and you have a gas fire- even for
'looks' - then the living room can be as warm as toast and the rest of the
house freezing.


The thinking was along those lines actually!

We didn't want the rest of the house "freezing", as such, but bits of it
could do with being a lot cooler than they are, the way things work at the
moment - the bedrooms and kitchen get too hot so we were thinking of ways to
a) lower the temps in those rooms which are not used a lot in the daytime
and b) lower the running costs a bit.

I assume TRVs would help? Are they as easy to fit as they look?

Opening the front door etc will cause a 'burst' of the heating but that
inrush of could air will need warming or it can give cold draughts in the
other rooms.


That's a good point.

On balance, I favour the thermostat in the hall.

Also, do a good job of draught excluding- that does wonders for the warm
'feel' of the house.


We've recently had double-glazing fitted, that should help a lot.

Thanks for the reply,

Si


  #4   Report Post  
Andy Hall
 
Posts: n/a
Default Central heating Q

On Tue, 29 Jul 2003 19:00:47 +0100, "Mungo \"two sheds\" Toadfoot"
wrote:

Hi peeps,

The thermostat that controls our central heating boiler is in the,
fairly small, hallway. Is this the best place for it?

If our living room and kitchen doors are closed and someone opens the front
door won't the stat think the house is freezing and fire up the heating?


Yes.

If
the stat's trying to get the hallway up to, say, 28 degrees, wouldn't the
rads in other parts of the house be getting hotter than they needed to?


Yes and no. There are two main components to heat loss - the first
being what is lost through the surfaces (walls, floor, ceiling, etc.)
and the second is heating the air. When you calculate heat losses
for radiator sizing (or use a program to do it), the surface losses
are accounted for by area, temperature difference and U value. The
heat required to warm the air is calculated on the basis that you are
heating the volume of air of the space at a certain number of air
changes per hour (generally 1-2 depending on the room, more for
kitchens and bathrooms.) Once the fabric of the building is warm,
the heat loss through the surfaces varies with the temperature
difference. If the building were completely cold and you turn on the
heating, you would also be putting heat into the thermal mass of the
building (mainly the bricks). However, once the fabric is warm,
opening the door for a short time is only going to mean that the air
needs to be reheated which does not require as long a run as the
initial start from totally cold. This would mean that the radiators
in the other rooms will run for longer than needed and the rooms will
overheat if you just have standard valves.



Our last house had the stat in the living room, which sounds a much better
idea to me - if the main room is warm then the rest of the house is too,
surely?


Again yes and no. Provided that you have no extra heat in there
such as a fire, you would get a reasonable result. Once you add
heat from another source, the effect will be to cause the room to be
warm enough and the CH only adding part of the heat. Its thermostat
will be satisfied earlier and the rest of the house will be cooler
than you may want. You can even get this effect if you have a
smallish but well insulated room and you get a number of visitors.
Each will add about 100W so 500W, which could be 25% of the heat
requirement would be enough to throw the system off.

I don't think that there is a perfect place. Kitchens and bathrooms
are out, so apart from hallways and stairs there isn't a huge choice.

Currently I have mine on an upstairs landing which is quite effective,
but I do also have an outside temperature sensor and I can program the
relative impact of one sensor vs. the other.



Also, I'm thinking of putting TRVs on all the rads so that the bedroom rads
can be turned down in the daytime. I'm guessing that they can just be
swapped with the existing valves (after draining down of course)?


Yes they can. Remember not to put one where the thermostat is going
to go or you will have two control systems fighting each other and the
system will likely run quite cold.


If I did this would it mean that I could leave the stat where it was? It'd
be a right pig to move and I'd rather not!


You could do. One solution you might like to consider is to use an
RF thermostat. The receiver can either go where the existing
thermostat is, or close to the wiring centre or boiler (i.e. where you
can tap into the wiring. With this arrangement you can take the
thermostat where you like and control that. In this case, having a
TRV on every radiator is more appropriate and then you simply turn the
one in the room where the thermostat is to fully open.

In any case, it is worth fitting a decent electronic type thermostat
because they operate more accurately and without the overshoot of the
bimetallic strip type. That would also have the effect of reducing
overheating in the rest of the house if the thermostat suddenly gets a
cool blast of air.









Any problems with this, or advice?

Ta,

Si


..andy

To email, substitute .nospam with .gl
  #5   Report Post  
Andy Hall
 
Posts: n/a
Default Central heating Q

On Tue, 29 Jul 2003 20:04:58 +0100, "Mungo \"two sheds\" Toadfoot"
wrote:


"Brian Reay" wrote in message
...

If the thermostat is in the living room and you have a gas fire- even for
'looks' - then the living room can be as warm as toast and the rest of the
house freezing.


The thinking was along those lines actually!

We didn't want the rest of the house "freezing", as such, but bits of it
could do with being a lot cooler than they are, the way things work at the
moment - the bedrooms and kitchen get too hot so we were thinking of ways to
a) lower the temps in those rooms which are not used a lot in the daytime
and b) lower the running costs a bit.

I assume TRVs would help? Are they as easy to fit as they look?


Yes they are. It used to be that you had to be sure to fit them so
that the flow went in a specific direction. Nowadays most are
reversible.

Otherwise, it's a fairly straightforward replacement exercise. One of
the biggest pains tends to be removing the olive from the existing
fitting to be able to put on the new nut and olive. From
experience, I do think it's worth buying decent TRVs like Drayton,
Invensys, Honeywell etc. A few pounds more but they do tend to last
more than proportionately longer IME. Generally the expanding
capsule in the head fails after a typical life of 7-10 years. You
can buy spare heads and change them if the body is still sound.



Another option if the plumbing is appropriate could be to fit a zone
valve with a timer/thermostat for the areas not wanted during the day.
You could then use a setback thermostat to just drop the temperature a
little.

I mentioned electronic thermostats in my other post. Another feature
of these is setback where you can drop the temperature at certain
times rather than off completely. Once adjusted suitably, you will
get greater comfort. Also it can be less expensive to run if you just
drop the temperature by 6 degrees or so overnight rather than
completely off. The reason is that you then don't need the massive
surge of heat in the morning to bring the building up to temperature
and the overshoot and waste that that can bring.
You do need to play around a little to set these effectively.



Opening the front door etc will cause a 'burst' of the heating but that
inrush of could air will need warming or it can give cold draughts in the
other rooms.


That's a good point.

On balance, I favour the thermostat in the hall.

Also, do a good job of draught excluding- that does wonders for the warm
'feel' of the house.


We've recently had double-glazing fitted, that should help a lot.


Yes it should, but you don't need to completely hermetically seal the
place or you will get other problems.




Thanks for the reply,

Si


..andy

To email, substitute .nospam with .gl


  #6   Report Post  
Mungo \two sheds\ Toadfoot
 
Posts: n/a
Default Central heating Q


"Roger Mills" wrote in
message ...

Having read all of this thread, I don't think you actually said whether
there is a radiator in the hall near to the thermostat.


No, I didn't, but there is so I won't fit a TRV to it - thanks.

If there *isn't*
then is hall is *not* a good place for the stat - because the system will

be
running open loop - and you'll get very random temperatures in all the
rooms.

If there *is* a rad near the stat, *don't* fit a thermostatic valve on

it -
even if you fit them to the rads in the other rooms - otherwise the 2

stats
will be fighting each other.

If you're prepared for something more major, I like the idea of zoning -
with a programmable stat controlling each zone. You can then have

different
zones coming on at different times (and can also have different

temperatures
at different times) to fit in with how you use your various rooms.


I fancy that too. Sounds a bit 'spensive though :O)

Si


  #7   Report Post  
IMM
 
Posts: n/a
Default Central heating Q


"Mungo "two sheds" Toadfoot" wrote in
message ...
Hi peeps,

The thermostat that controls our central heating boiler is in the,
fairly small, hallway. Is this the best place for it?

If our living room and kitchen doors are closed and someone opens the

front
door won't the stat think the house is freezing and fire up the heating?

If
the stat's trying to get the hallway up to, say, 28 degrees, wouldn't the
rads in other parts of the house be getting hotter than they needed to?

Our last house had the stat in the living room, which sounds a much better
idea to me - if the main room is warm then the rest of the house is too,
surely?

Also, I'm thinking of putting TRVs on all the rads so that the bedroom

rads
can be turned down in the daytime. I'm guessing that they can just be
swapped with the existing valves (after draining down of course)?

If I did this would it mean that I could leave the stat where it was? It'd
be a right pig to move and I'd rather not!

Any problems with this, or advice?


If you are having TRVs on all rads (check with the boiler instructions that
you can do this), dispense with the wall stat. Install a Grundfoss Alpha
variable speed pump which are notably quieter than the old pumps as they
match their power to the heating load and flow especially if you have TRVs.
The regs say you must have a "control interlock" that cuts out the burner
when the house does not require heating. This can be done by having a flow
switch on the return pipe. If the TVRs all close down the pump switches
itself, the flowswitch say no flow and the burners is off too. One TVR
opens up and the pump switches on, the flow switch detects flow and the
burner lights.

The boiler may require a minimum flow through the heat exchanger. Insert a
by-pass with a gate valve in it from the flow to the return after the pump.
With all rads off the valve must be set to give minimum flow through the
boiler. The flow switch must be before the by-pass tee on the return.
Boiler - return pipe - by-pass tee - flowswitch.



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  #8   Report Post  
Jonathan@Home
 
Posts: n/a
Default Central heating Q


Another option if the plumbing is appropriate could be to fit a zone
valve with a timer/thermostat for the areas not wanted during the day.
You could then use a setback thermostat to just drop the temperature a
little.



I wanted to do this and asked Honeywell for advice, as I have a Honeywell
CM67 ChronoTherm (fancy thermostat). A very nice man at Honeywell sent me a
wiring diagram for three zones and hot water, I actually wanted 4 zones and
no HW control but it is easy to see how it is all wired up.

Cheers
Jonathan


  #9   Report Post  
David
 
Posts: n/a
Default Central heating Q

"IMM" wrote in message ...

If you are having TRVs on all rads (check with the boiler instructions that
you can do this), dispense with the wall stat.


You are a complete numpty.

Building regs require that you have a room thermostat and at least
TRV's on all radiators in sleeping areas (of course you can have
more).
They also state quite clearly that the use or TRV's alone are not
sufficient.

You are required to comply with the building regs if you make any
changes to your heating system to bring it up to standard.

Do you regularly fit systems like this? If so, the BCO would be very
interested I'm sure.
  #10   Report Post  
Christian McArdle
 
Posts: n/a
Default Central heating Q

Building regs require that you have a room thermostat and at least
TRV's on all radiators in sleeping areas (of course you can have
more).


Actually, much as I hate to say it, IMM is correct here.

The regulations don't specify that TRVs are used at all. The requirements
are that the rooms are individually controlled, which could be TRVs or a
separate zone with room programmer/thermostat.

They also state quite clearly that the use or TRV's alone are not
sufficient.


The regulations state that boiler interlock is required. Although
traditionally done using a room thermostat that controls the boiler
directly, it is not a requirement to do it this way. A flow switch on an
automatic bypass loop, for example, is perfectly adequete and compliant to
turn the boiler off when all the TRVs close.

Obviously, TRVs alone are not enough, as you say. However, TRVs with a
bypass loop and flow switch are. As long as the boiler switches off when the
heating load is satisfied, the building regulations requirement is met.

Some quotes of Approved Document L1:

1.38

Temperature control could be effected by room thermostats and/or
thermostatic radiator valves or any other suitable temperature sensing
devices, together
with appropriate control devices.

1.41 (b)
Where it is proposed to effect control by thermostatic radiator valves, a
room thermostat (or other device such as a flow switch) should also be
provided to switch off the boiler when there is no demand for heating or hot
water.

Christian.




  #11   Report Post  
IMM
 
Posts: n/a
Default Central heating Q


"Andy Hall" wrote in message
...

I mentioned electronic thermostats in my
other post. Another feature
of these is setback where you can drop
the temperature at certain
times rather than off completely.
Once adjusted suitably, you will
get greater comfort. Also it can be less
expensive to run if you just
drop the temperature by 6 degrees
or so overnight rather than
completely off.


Do have any figures to prove this? Unless it is sluggish UFH, setting the
temp back does not result in greater economy. In the 1960s the electricity
boards had a slogan "Lag It And Leave It", saying lag a cylinder and leave
the immersion heater on 24/7. Under tests this was slagged as highly
uneconomical. Switching the immersion on when needed or on a clock was
proven to be far more economical.

In commercial buildings a low temp limit of 10C is maintained as under this
temp the fabric of the building and its furnishings may be effected. A good
optimum start stat as the Honeywell CM76 is the best way. It works out the
right time to start the system to reach the target start temp.



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  #12   Report Post  
Andy Hall
 
Posts: n/a
Default Central heating Q

On Wed, 30 Jul 2003 08:44:05 +0100, "Jonathan@Home"
wrote:

Andy,

What thermostat are you using? I have an outside sensor for my CM67 but
haven't got round to connecting up, I do though have a natty little module
that gets the time from the Rugby radio clock signal; so I never ahve to
worry about the spring and autimn time changes. It connects via a couple of
pins internaly and I'm wondering if I can slave the other zone controllers
off this one with a bit if wiring to share it via a terminal box.


Cheers
Jonathan


My boiler (MAN Micromat) has its own control system and sensors.

The boiler itself modulates the burner via use of the fan speed and
will give an output from 4kW up to full power. THe pump is internal
and it modulates that as well, linearly. There are sensors for the
flow and return water temperatures and it will run quite well just
using those if you have a system with TRVs. As they adjust, it will
vary heat output accordingly.

The manufacturer supplies an outside temperature sensor with the
boiler which can be used to provide feedforward control. Since a
house as a fairly substantial thermal time constant, sensing a change
in outside temperature (especially if there is a relatively sudden
one) allows the boiler to begin to adjust for it rather than waiting
for the disturbance to show up in the house. This results in better
temperature control and economy than can be achieved with an inside
sensor alone.

One can also add an internal controller that is specific to the
boiler, (but made by Siemens (Landis & Gyr) ). This hooks into the
boiler and allows it to measure the actual room temperature. A
conventional on/off thermostat or a proportional control type work by
turning the heat demand on and off, albeit to good effect with a
proportional type if adjusted correctly.

On this controller, it's possible to do all of the normal setback
adjustments, and the boiler microprocessor begins to learn the heating
behaviour of the house. You can also adjust the relative sensitivity
and effect of the inside control and the outside control if you want
to optimise further. One effect, for example is that sometimes the
boiler will fire up at very low output just after sunset and the
radiators will become tepid - about 40 degrees - increasing if need
be. The boiler will also accept a conventional or proportional
controller, although control is then not as fine.

This article explains a little about the principles of feedforward in
a control system, albeit an industrial process. The concept is
similar for a CH system of this type.

http://www.pc-education.mcmaster.ca/...arlin_2002.pdf

There's an optional bullet type sensor for DHW cylinders which goes
into a pocket in the cylinder. This hooks directly to the boiler,
allowing it to sense water temperature directly rather than from an on
off thermostat. This allows it to detect rate of change of
temperature among other things. For example if the set point is 60
degrees and I am just drawing off little bits of water, the boiler
ignores it until the temperature reaches 55 degrees, at which point it
fires up and does a water reheat cycle at full power, cylinder only.
If I run a shower or draw a bath, it sees a rapid drop in temperature
and responds more quickly. There is also a mechanism whereby the
boiler begins to throttle back as the set point is approached so that
it doesn't overshoot.

The manufacturer even supplies optional PC software so that you can
log its every move and even display temperature, power level etc
graphs should you be so minded. I take the data from mine and use it
for energy consumption recording among other things.


For the CM67, have a look at this application note.

http://content.honeywell.com/uk/homes/files/pag106.pdf

It rather looks as though the outside sensor is there to display
temperature on the room thermostat as opposed to taking it into
account for control purposes. It may be worth asking Honeywell
though.

As regards sharing the clock module, I think it will depend on how it
interfaces with the rest of the logic of the controller.
If the module simply outputs the time based on the MSF signal (which
it could) then it may work. OTOH, if the main microprocessor has to
program the chip in the time module or send commands to tell the chip
to provide the time then it probably won't work to drive multiple
controllers from one time module.


..andy

To email, substitute .nospam with .gl
  #13   Report Post  
David
 
Posts: n/a
Default Central heating Q

"Christian McArdle" wrote in message .net...
Building regs require that you have a room thermostat and at least
TRV's on all radiators in sleeping areas (of course you can have
more).


Some quotes of Approved Document L1:

1.38

Temperature control could be effected by room thermostats and/or
thermostatic radiator valves or any other suitable temperature sensing
devices, together
with appropriate control devices.

1.41 (b)
Where it is proposed to effect control by thermostatic radiator valves, a
room thermostat (or other device such as a flow switch) should also be
provided to switch off the boiler when there is no demand for heating or hot
water.

Christian.


Gotcha. Mis-read the documentation I had (slightly) - my source
didn't have the line on 'flow switch'. I stand corrected, and promise
to check the source document in future and not something second hand.

Now I have a question - Maybe not in the regs, but I thought it was
considered 'best practice' to have the mix I went for - TRV's in some
places, and a room thermostat for overall control (along with a
conventional timer). And preferably a programmable stat. I just
can't find the reference for that information ATM.
  #14   Report Post  
IMM
 
Posts: n/a
Default Central heating Q

"David" wrote in message
om...
"Christian McArdle" wrote in message

.net...
Building regs require that you have a room thermostat and at least
TRV's on all radiators in sleeping areas (of course you can have
more).


Some quotes of Approved Document L1:

1.38

Temperature control could be effected by room thermostats and/or
thermostatic radiator valves or any other suitable temperature sensing
devices, together
with appropriate control devices.

1.41 (b)
Where it is proposed to effect control by thermostatic radiator valves,

a
room thermostat (or other device such as a flow switch) should also be
provided to switch off the boiler when there is no demand for heating or

hot
water.

Christian.


Gotcha. Mis-read the documentation I had (slightly) - my source
didn't have the line on 'flow switch'. I stand corrected, and promise
to check the source document in future and not something second hand.

Now I have a question - Maybe not in the regs, but I thought it was
considered 'best practice' to have the mix I went for - TRV's in some
places, and a room thermostat for overall control (along with a
conventional timer). And preferably a programmable stat. I just
can't find the reference for that information ATM.


The best is what I explained. Individual control in all rooms and a flow
switch to act the "interlock". The regs state "or other device such as a
flow switch". "Any other device" are the key words.




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  #15   Report Post  
Christian McArdle
 
Posts: n/a
Default Central heating Q

Now I have a question - Maybe not in the regs, but I thought it
was considered 'best practice' to have the mix I went for -
TRV's in some places, and a room thermostat for overall control
(along with a conventional timer). And preferably a programmable
stat. I just can't find the reference for that information ATM.


Not "best" practice, but probably the most common one, and compliant with
Part L. The regs seem to suggest you have to have independent control of
living and sleeping areas. It suggests that TRVs, room thermostats or other
devices can be used to achieve this. It doesn't say what method is best.

The "best" method that is easy to make from commonly available parts is to
zone off each room and have each have its own programmer/thermostat so that
each room can have its own time and temperature settings. (i.e. dining room
could be set to run on boost only before you eat (unless you eat religiously
at the same time every day), bedrooms off until 9pm, then warm, but getting
progressively colder through the night etc). Not a TRV in sight in such a
system. Outside temperature compensation is good too, if it can be made to
work with a multizone system.

The absolute best system would have analogue temperature sensors in each
room, an analogue outside temperature sensor, analogue valve actuators on
each radiator, analogue power request signal to the boiler and pump,
analogue sensors on the flow and return lines, and a little computer box to
take the inputs, compare with your required temperature profiles for each
room and drive the actuators, boiler and pump as required by a very
complicated set of algorithms (probably neural net based learning type) that
predict temperature changes, pre-empt required temperature changes, prevent
boiler cycling and keep each room precisely at its individually selected
temperature, within the capability of the system to do so.

Christian.





  #16   Report Post  
IMM
 
Posts: n/a
Default Central heating Q


"Christian McArdle" wrote in message
. net...

The best is what I explained. Individual
control in all rooms and a flow switch to
act the "interlock". The regs state "or other
device such as a flow switch". "Any other
device" are the key words.


Reasonable, but not best, surely.


Not the best of course, but cheap and effective individual control in each
room. The best will be complicated and expensive.

Although you get individual temperature
control in each room using that method,
it is better to have individual time
control in each room as well, as rooms
in a house have very different usage
profiles.


This is true, but expensive and more complexity.

This could be done with seperate
programmer thermostats in each
room, which could drive conventional
2 port valves with microswitch boiler
interlock,


A CM67 and zone valve for each room? Nice but expensive.

or modified TRVs that take a control
signal, with boiler interlock provided by
flow switches,


Very expensive as a controller will be required to mosulate the TVR valve,
and then a timer for that room too. Ouch!

or the logically ORed
outputs from the programmers.


The second approach (i.e. logically
ORed outputs) gets past the problems
associated with flow switch interlocks,
which although good at stopping the
flow, aren't so good at noticing that
TRVs have opened again without pulsing
the pump regularly.


That is why you use an Alpha pump.

(Obviously an automatic bypass valve
is essential if the interlock has the
possibility of not corresponding directly with TRV
position).


I suppose you could combine the two
methods and pulse the pump when the
logical signal indicates the valves should
be open (given a minute's delay
for the TRV to respond). That way, the
interlock operation might be more
reliable in the event of a TRV's failure to
respond to its signal, but will
prevent pump pulsing when the system
"knows" that no heat is required
already.


You are delving into the realms of commercial systems, where say a large
conference room would have its own controls. In a domestic house? Not
likely.

The cheapest and more practical is what is suggested: Alpha pump, by-pass,
flowswitch and TRVs all around. Then split the system into two zones,
probably up and down, using a stat/programmer in each zone and one zone
valve. Cheap, easy, simple, economical to run and will satisfy most peoples
needs.



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  #17   Report Post  
Christian McArdle
 
Posts: n/a
Default Central heating Q

The cheapest and more practical is what is suggested: Alpha pump,
by-pass, flowswitch and TRVs all around. Then split the system
into two zones,


Obviously, the system would have been overspecified, but it was an example
of the "best" rather than "best value". The system I'm just doing myself
will be converted to up and down zones with a 2 port valve and programmable
controller each in the lounge and master bedroom. The other rooms will have
to fend for themselves on TRVs.

A system like that is pretty cheap, easy to install (or even modify an
existing system to) and allows separate timing for the sleeping and living
room areas as a whole, which is quite an advantage when the time usage
profiles are so different between the two. The differences between 2
bedrooms, though, aren't quite so great, so might not justify the provision
of additional zoning.

BTW, how does the Alpha know when to restart? Does it "poll" at a certain
frequency to check the resistance?

Christian.


  #18   Report Post  
Andy Hall
 
Posts: n/a
Default Central heating Q

On Wed, 30 Jul 2003 12:15:43 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .

I mentioned electronic thermostats in my
other post. Another feature
of these is setback where you can drop
the temperature at certain
times rather than off completely.
Once adjusted suitably, you will
get greater comfort. Also it can be less
expensive to run if you just
drop the temperature by 6 degrees
or so overnight rather than
completely off.


Do have any figures to prove this?


Actually yes, but first let me make the point that I did say *can* be
less expensive, not *would* be. It would depend on the circumstances
I am sure.

Remember that I said that I can gather all of the boiler data to a log
on a PC. This includes fan speed (which relates to power level and
gas usage), pump speed, flow and return temperatures and inside and
outside temperatures, as well as whether the boiler is driving CH or
DHW..

Last winter I did experiments over a few week-long periods with a 5
degree setback from 21 to 16 degrees and without setback at all.
I took out the DHW use and looked at the CH only and matched 24 hour
periods when the outside temperature pattern was similar.

There was, on average, a 3-5% lower use of gas when setback was used.


Unless it is sluggish UFH, setting the
temp back does not result in greater economy.


It isn't, but UFH is towards the extreme end of the scale in terms of
thermal inertia. A house with conventional system and masonry walls
still has a thermal inertia, albeit not as great.

In the 1960s the electricity
boards had a slogan "Lag It And Leave It", saying lag a cylinder and leave
the immersion heater on 24/7. Under tests this was slagged as highly
uneconomical. Switching the immersion on when needed or on a clock was
proven to be far more economical.


At that point it probably did. WIth today's insulation, and I have a
100mm layer around my cylinder, the heat loss is negligible - a few
watts. I therefore leave the hot water on 24*7 because it makes no
sense to turn it off. It is very rare that the boiler does a hot
water cycle between 2300 and 0700 unless hot water is drawn.
Before you ask the question, yes I have data for that as well.



..andy

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  #19   Report Post  
IMM
 
Posts: n/a
Default Central heating Q


"Christian McArdle" wrote in message
. net...

The cheapest and more practical is what
is suggested: Alpha pump, by-pass,
flowswitch and TRVs all around. Then
split the system into two zones,


Obviously, the system would have been
overspecified, but it was an example
of the "best" rather than "best value".


Best, yes. Over engineered, probably yeas for an average home.

The system I'm just doing myself
will be converted to up and down
zones with a 2 port valve and programmable
controller each in the lounge and master
bedroom. The other rooms will have
to fend for themselves on TRVs.


I did this 10 years ago for a relative, except they had the downstairs stat
in the hall, which acted more as a high limit rather than a comfort control.
The upsairs is only on in tgemmornings and evenings, and if heat is wanted
outside these times, just flick the override switch. Now I would have two
simple timers for each zone, TVRs all around and an Alpha.

A system like that is pretty cheap,
easy to install (or even modify an
existing system to)


The pipework to split the system may be quite a task in some homes.

and allows separate timing for the
sleeping and living room areas as
a whole, which is quite an advantage
when the time usage profiles are so
different between the two.


The one I did saved about 20-30% in fuel. It was a big house, so made all
the difference. having two separate zones is a cheap undertaking, yet saves
more than fitting a condensing boiler.

The differences between 2
bedrooms, though, aren't quite
so great, so might not justify the provision
of additional zoning.

BTW, how does the Alpha know when
to restart? Does it "poll" at a certain
frequency to check the resistance?


It starts up occasionally to detect the pressure. On start up they can make
a stammering sound. This is normal as it judders by switching off and on to
dislodge any debris in the pipework.

A normal pump can be used except that a timer would have to be activated to
turn the pump when the flowswitch cuts out. A cheap one can got from RS,
Maplin, etc, and some thought into the operation and wiring. using an Alpha
and flowswitch is simple and easy.




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  #20   Report Post  
IMM
 
Posts: n/a
Default Central heating Q


"Andy Hall" wrote in message
...
On Wed, 30 Jul 2003 12:15:43 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .

I mentioned electronic thermostats in my
other post. Another feature
of these is setback where you can drop
the temperature at certain
times rather than off completely.
Once adjusted suitably, you will
get greater comfort. Also it can be less
expensive to run if you just
drop the temperature by 6 degrees
or so overnight rather than
completely off.


Do have any figures to prove this?


Actually yes, but first let me make the point that I did say *can* be
less expensive, not *would* be. It would depend on the circumstances
I am sure.


There was, on average, a 3-5% lower
use of gas when setback was used.


What about comparison to optimised start and stop?

In the 1960s the electricity
boards had a slogan "Lag It And Leave It", saying lag a cylinder and

leave
the immersion heater on 24/7. Under tests this was slagged as highly
uneconomical. Switching the immersion on when needed or on a clock was
proven to be far more economical.


At that point it probably did. WIth today's insulation, and I have a
100mm layer around my cylinder,


The point is that the older cylinders can be equated to heating systems. Not
so much today.


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  #21   Report Post  
Andy Hall
 
Posts: n/a
Default Central heating Q

On Wed, 30 Jul 2003 17:22:21 +0100, "Christian McArdle"
wrote:

The cheapest and more practical is what is suggested: Alpha pump,
by-pass, flowswitch and TRVs all around. Then split the system
into two zones,


Obviously, the system would have been overspecified, but it was an example
of the "best" rather than "best value". The system I'm just doing myself
will be converted to up and down zones with a 2 port valve and programmable
controller each in the lounge and master bedroom. The other rooms will have
to fend for themselves on TRVs.

A system like that is pretty cheap, easy to install (or even modify an
existing system to) and allows separate timing for the sleeping and living
room areas as a whole, which is quite an advantage when the time usage
profiles are so different between the two. The differences between 2
bedrooms, though, aren't quite so great, so might not justify the provision
of additional zoning.

BTW, how does the Alpha know when to restart? Does it "poll" at a certain
frequency to check the resistance?



The Alpha doesn't stop and start of its own accord, it simply winds
down to a lower power with increasing resistance.
The purpose of the flow switch would have to be to detect when TRVs
had closed to a sufficient point that an automatic valve on a bypass
opens - i.e. flow starts through the bypass and the switch operates.

This would need a relay, since the logic is wrong, and also I wonder
how the bypass needed for the boiler would work. That would need an
extra time switch or relays to work properly I think since it needs to
run uncondtionally vis-a-vis what the CH is doing.


..andy

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  #22   Report Post  
Andy Hall
 
Posts: n/a
Default Central heating Q

On Wed, 30 Jul 2003 16:25:10 +0100, "Christian McArdle"
wrote:

Now I have a question - Maybe not in the regs, but I thought it
was considered 'best practice' to have the mix I went for -
TRV's in some places, and a room thermostat for overall control
(along with a conventional timer). And preferably a programmable
stat. I just can't find the reference for that information ATM.


Not "best" practice, but probably the most common one, and compliant with
Part L. The regs seem to suggest you have to have independent control of
living and sleeping areas. It suggests that TRVs, room thermostats or other
devices can be used to achieve this. It doesn't say what method is best.

The "best" method that is easy to make from commonly available parts is to
zone off each room and have each have its own programmer/thermostat so that
each room can have its own time and temperature settings. (i.e. dining room
could be set to run on boost only before you eat (unless you eat religiously
at the same time every day), bedrooms off until 9pm, then warm, but getting
progressively colder through the night etc). Not a TRV in sight in such a
system. Outside temperature compensation is good too, if it can be made to
work with a multizone system.

The absolute best system would have analogue temperature sensors in each
room, an analogue outside temperature sensor, analogue valve actuators on
each radiator, analogue power request signal to the boiler and pump,
analogue sensors on the flow and return lines, and a little computer box to
take the inputs, compare with your required temperature profiles for each
room and drive the actuators, boiler and pump as required by a very
complicated set of algorithms (probably neural net based learning type) that
predict temperature changes, pre-empt required temperature changes, prevent
boiler cycling and keep each room precisely at its individually selected
temperature, within the capability of the system to do so.

Christian.


I'm in the middle of implementing just such an arrangement of
controls. It's helpful to be able to take data from the boiler to
determine what it is doing, since I want to take advantage of its
capabilities rather than fighting them.

The algorithms are certainly the most complex part, especially when
you have rooms used quite variably.

Temperature sensing is very easy as is the analogue valve actuating
part.


..andy

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  #23   Report Post  
IMM
 
Posts: n/a
Default Central heating Q


"Andy Hall" wrote in message
...

BTW, how does the Alpha know when to restart? Does it "poll" at a certain
frequency to check the resistance?


The Alpha doesn't stop and start of
its own accord, it simply winds
down to a lower power with increasing resistance.


I was informed by a Grundfos rep when they first came out that is stopped.
Maybe he didn't know too much as it was a brand new product.

The purpose of the flow switch would
have to be to detect when TRVs
had closed to a sufficient point that an
automatic valve on a bypass
opens - i.e. flow starts through the bypass
and the switch operates.


An auto by-pass would not be opened by an Alpha. The valve requires pump
pressure to open it. When the Alpha detects pressure it reduced the speed
thinking TRVs are cloosed down. A permanent by-pass is the best option.
The flow switch detecting if the TRVs are closed should not be in the
circuit of the by-pass.

This would need a relay, since the logic is wrong, and also I wonder
how the bypass needed for the boiler would work. That would need an
extra time switch or relays to work properly I think since it needs to
run uncondtionally vis-a-vis what the CH is doing.


A flow switch would switch off the boiler/burner, maybe via thermostat
terminals. The Alpha can be left to run as



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  #24   Report Post  
Andy Hall
 
Posts: n/a
Default Central heating Q

On Wed, 30 Jul 2003 18:05:49 +0100, "IMM" wrote:



Actually yes, but first let me make the point that I did say *can* be
less expensive, not *would* be. It would depend on the circumstances
I am sure.


There was, on average, a 3-5% lower
use of gas when setback was used.


What about comparison to optimised start and stop?


That was with optimised start and stop. The controller does that
anyway when ramping between two temperatures whether it has been
completely off or just at a lower set point.


In the 1960s the electricity
boards had a slogan "Lag It And Leave It", saying lag a cylinder and

leave
the immersion heater on 24/7. Under tests this was slagged as highly
uneconomical. Switching the immersion on when needed or on a clock was
proven to be far more economical.


At that point it probably did. WIth today's insulation, and I have a
100mm layer around my cylinder,


The point is that the older cylinders can be equated to heating systems. Not
so much today.


Probably. Really with decent insulation on the cylinder, whether the
timer would allow the water to be heated 24*7 or just 16*7 becomes
largely irrelevant.


..andy

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  #25   Report Post  
Andy Hall
 
Posts: n/a
Default Central heating Q

On Wed, 30 Jul 2003 18:25:49 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .

BTW, how does the Alpha know when to restart? Does it "poll" at a certain
frequency to check the resistance?


The Alpha doesn't stop and start of
its own accord, it simply winds
down to a lower power with increasing resistance.


I was informed by a Grundfos rep when they first came out that is stopped.
Maybe he didn't know too much as it was a brand new product.


Possibly it did to begin with. I have one for my workshop circuit and
it definitely doesn't stop, although it it does drop power level
considerably. I tested it using the ball valves that I have to
isolate it.

One thing that it does do is to pulse a few times when starting.
Apparently this is to help clear any accumulated air.




The purpose of the flow switch would
have to be to detect when TRVs
had closed to a sufficient point that an
automatic valve on a bypass
opens - i.e. flow starts through the bypass
and the switch operates.


An auto by-pass would not be opened by an Alpha. The valve requires pump
pressure to open it.


When the Alpha detects pressure it reduced the speed
thinking TRVs are cloosed down.

I believe it will still deliver enough to open an auto bypass on its
bottom end setting.


A permanent by-pass is the best option.
The flow switch detecting if the TRVs are closed should not be in the
circuit of the by-pass.


The trouble is that flow switches (apart from expensive industrial
process control ones) are not that accurate in terms of operating at a
certain rate. They tend to be either a gravity or spring assisted
mechanism. I have one on the secondary side of my workshop
circuit. The pump is located in the workshop and operated by a
thermostat. When water flows, the flow switch detects it and
operates a 2 port zone valve to the primary side of the heat
exchanger, and of course fires up the boiler. This way, I don't need
any electrical control signals between the locations.



..andy

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  #26   Report Post  
IMM
 
Posts: n/a
Default Central heating Q


"Andy Hall" wrote in message
...
On Wed, 30 Jul 2003 18:25:49 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .

BTW, how does the Alpha know when to restart? Does it "poll" at a

certain
frequency to check the resistance?

The Alpha doesn't stop and start of
its own accord, it simply winds
down to a lower power with increasing resistance.


I was informed by a Grundfos rep when they first came out that is

stopped.
Maybe he didn't know too much as it was a brand new product.


Possibly it did to begin with. I have one for my workshop circuit and
it definitely doesn't stop, although it it does drop power level
considerably. I tested it using the ball valves that I have to
isolate it.


How slow does it get to? If it is very slow pumping nothing it is probably
OK.

When the Alpha detects pressure it reduced the speed
thinking TRVs are cloosed down.


I believe it will still deliver enough to open
an auto bypass on its bottom end setting.


If that is the case then all soved by inserting an auto by-pass. The pump
just keeps turning until a TVR opens up, the the auyto by-pass will slowly
close.

A permanent by-pass is the best option.
The flow switch detecting if the TRVs are closed should not be in the
circuit of the by-pass.


The trouble is that flow switches (apart from expensive industrial
process control ones) are not that accurate in terms of operating at a
certain rate. They tend to be either a gravity or spring assisted
mechanism.


The unit sold by DPS uses a magnetic switch. They are quite accurate in
detecting 2 litres flow per min. I have used them and they are fine.

I have one on the secondary side of my workshop
circuit. The pump is located in the workshop and operated by a
thermostat.


A pipe stat detecting heat?

When water flows, the flow switch detects it and
operates a 2 port zone valve to the primary side of the heat
exchanger, and of course fires up the boiler. This way, I don't need
any electrical control signals between the locations.




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  #27   Report Post  
Andy Hall
 
Posts: n/a
Default Central heating Q

On Wed, 30 Jul 2003 23:31:20 +0100, "IMM" wrote:



I was informed by a Grundfos rep when they first came out that is

stopped.
Maybe he didn't know too much as it was a brand new product.


Possibly it did to begin with. I have one for my workshop circuit and
it definitely doesn't stop, although it it does drop power level
considerably. I tested it using the ball valves that I have to
isolate it.


How slow does it get to? If it is very slow pumping nothing it is probably
OK.


I haven't measured it, but the pump certainly backs right off as the
flow is restricted by closing the valve. The data sheet says that
the minimum level is around 0.4 cu.m/hr






The trouble is that flow switches (apart from expensive industrial
process control ones) are not that accurate in terms of operating at a
certain rate. They tend to be either a gravity or spring assisted
mechanism.


The unit sold by DPS uses a magnetic switch. They are quite accurate in
detecting 2 litres flow per min. I have used them and they are fine.


This is what I'm using, although I did have an issue with DPS. They
originally sent a duff one that had obviously been used before in
something. Admittedly they did immediately send a new replacement,
but I don't appreciate receiving secondhand items. I am not sure
that I would do business with them again.

The switch is certainly sensitive so does its job as I require it.
However, it has no form of adjustment, so in an application where the
need was to control something based on a specific flow rate I am not
sure how successful it would be. Also, if the switch were used to
control the pump, you would create positive feedback. The switch
operates to stop the pump when the flow stops. However when the flow
does stop the switch operates again and the pump starts. Some form
of logic using relays such that the flow switch triggers the pump
going off and it stays off until some other event starts it again.
Something like the thermostat causing heat demand might have to be the
means to reset everything.



I have one on the secondary side of my workshop
circuit. The pump is located in the workshop and operated by a
thermostat.


A pipe stat detecting heat?


No, the logic is the other way round. The thermostat in the
workshop is a room type . In fact I did rather well. I happened to
be in Homebase one day (I don't normally use them because of their
poor customer service) and they had a table of clearance items. I
picked up a Landis & Staefa REV100 controller with time setting, set
back, proportional control and LCD touch screen for £12. List price
is nearly £100. There's even a set of auxiliary switch contacts so
that you can override the heating to off. Apparently the Germans use
this feature connected to a window switch so that when they take the
bedclothes and hang them over the balcony rail of the apartment in the
morning, leaving the window open, the heating is cut off.
For me it's ideal because I can automatically turn off the heating
when I open the door of the workshop for any length of time.

The controller simply turns the pump in the workshop on and off as
required. This causes water to flow in the secondary circuit.
This is picked up by the flow switch in the house and that in turn
operates the motorised valve controlling flow from the primary circuit
through the heat exchanger.

It works quite effectively. Ultimately I'll tie it in to the rest of
the house system probably using some form of RF telemetry.




..andy

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  #28   Report Post  
IMM
 
Posts: n/a
Default Central heating Q

"Andy Hall" wrote in message
...
On Wed, 30 Jul 2003 18:25:49 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .

BTW, how does the Alpha know when to restart? Does it "poll" at a

certain
frequency to check the resistance?

The Alpha doesn't stop and start of
its own accord, it simply winds
down to a lower power with increasing resistance.


I was informed by a Grundfos rep when they first
came out that it stopped.
Maybe he didn't know too much as it was a
brand new product.


Possibly it did to begin with. I have one for my workshop circuit and
it definitely doesn't stop, although it it does drop power level
considerably. I tested it using the ball valves that I have to
isolate it.


Polyplumb and Speedfit use the Grundfos Alpha in their UFH systems. When
all the zones are closed by electric actuators the pump is still running.
The pump clearly can pump against a total stop when wound down to its
minimum speed without any adverse affects. Having an auto by-pass valve or
a fixed by-pass will make no difference. Just insert a flow switch on the
return and all rads can have TRVs and no electric room stat.



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  #29   Report Post  
Rob
 
Posts: n/a
Default


From: "Andrew Gabriel"
Subject: Central heating Q.
Date: 09 February 2005 23:42


If one end is a thermostatic radiator valve, then just turning
that off probably isn't good enough -- they don't usually have
an 'off' position, just a low or frost position. You need to
remove the thermostatic head and replace it with the blind cap
which comes with the valve, and will seal it off regardless of
the temperature.


Good advice. I took a radiator off, turned the TRV off (as I thought)
and went away for Christmas. Cold snap, TRV opens, new wood floor
flooded. Not a Happy New Year. :-(

Rob




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