I have two questions that I am sure you can help me with.

1. I have been told that it is a requirement to have a room thermostat on
the heating system even if every radiator has a thermostatic valve. Is this
the case? It would seem to be a nonsense.

2. Because of the proposed ground floor location of our new hot water
cylinder our Aga will not be able to heat it on a gravity thermosiphon. One
installer said a simple slow pumped system would work (with expansion tank
etc of course) - another said it would not. Any views?

Thanks

On Sat, 16 Jul 2005 22:13:45 +0000 (UTC), "Hzatph"
wrote:

I have two questions that I am sure you can help me with.

1. I have been told that it is a requirement to have a room thermostat on
the heating system even if every radiator has a thermostatic valve. Is this
the case? It would seem to be a nonsense.

There should be a lock-out for the boiler. The normal way is not to
have a TRV in one room and to put a room thermostat in there. The
boiler will then be turned off completely.


2. Because of the proposed ground floor location of our new hot water
cylinder our Aga will not be able to heat it on a gravity thermosiphon. One
installer said a simple slow pumped system would work (with expansion tank
etc of course) - another said it would not. Any views?


I have a natural gas Aga, although don't use it for hot water.

With a gravity arrangement, the heat transfer is relatively slow.
You don't say which fuel type that you have on the Aga, but the NG one
has a maximum input of around 5kW. My concern would be that pumping
the circuit would result in greater heat transfer rate than gravity
and that the heat in the cooker store would then be depleted.

You could call Aga-Rayburn's technical support in Telford. I have
found them pretty good.

The Aga is a great cooker, but if you have an alternative means other
than electricity to heat the water, then that would be better. You
could then go for a fast recovery cylinder which could take
substantially more heat transfer.




--

..andy

To email, substitute .nospam with .gl

Hzatph wrote:

I have two questions that I am sure you can help me with.

1. I have been told that it is a requirement to have a room thermostat on
the heating system even if every radiator has a thermostatic valve. Is this
the case? It would seem to be a nonsense.

You need an overall sta or a flow switch to stop the boiler when all the
rad stats have shut down..

2. Because of the proposed ground floor location of our new hot water
cylinder our Aga will not be able to heat it on a gravity thermosiphon. One
installer said a simple slow pumped system would work (with expansion tank
etc of course) - another said it would not. Any views?

Not sure on this pioint - aga themselves may know. I can't see why a
pump on a gravity system would not work tho.


Thanks

Andy Hall wrote:

On Sat, 16 Jul 2005 22:13:45 +0000 (UTC), "Hzatph"
wrote:


I have two questions that I am sure you can help me with.

1. I have been told that it is a requirement to have a room thermostat on
the heating system even if every radiator has a thermostatic valve. Is this
the case? It would seem to be a nonsense.


There should be a lock-out for the boiler. The normal way is not to
have a TRV in one room and to put a room thermostat in there. The
boiler will then be turned off completely.


2. Because of the proposed ground floor location of our new hot water
cylinder our Aga will not be able to heat it on a gravity thermosiphon. One
installer said a simple slow pumped system would work (with expansion tank
etc of course) - another said it would not. Any views?



I have a natural gas Aga, although don't use it for hot water.

With a gravity arrangement, the heat transfer is relatively slow.
You don't say which fuel type that you have on the Aga, but the NG one
has a maximum input of around 5kW. My concern would be that pumping
the circuit would result in greater heat transfer rate than gravity
and that the heat in the cooker store would then be depleted.

You could call Aga-Rayburn's technical support in Telford. I have
found them pretty good.

The Aga is a great cooker, but if you have an alternative means other
than electricity to heat the water, then that would be better. You
could then go for a fast recovery cylinder which could take
substantially more heat transfer.



I agree totally. The aga itself is a 24x7 room heater with a crude, but
effectoive cokker bolted into it.

It is NOT a water heater by any stretch of te imagination: Use oil boiler.

The only justification for using it for water heating is if you have an
electricfity supply problem and like hot baths by candlelight...

Interesting responses thank you. Giving Aga a call sounds a great idea and I
will do that. The pumped system will need to be turned right down so as not
to exceed the modest heat output capability of the Aga which is oil by the
way. I don't really want to run a 240,000 BTU boiler just to heat a water
cylinder in summer. The boiler will feed something like 28 radiators so the
prospect of all being shut down sounds unlikely - a no-flow switch closing
down the boiler sounds much more sensible than a room thermostat in one
room.

On Sun, 17 Jul 2005 07:18:11 +0000 (UTC), "Hzatph"
wrote:

Interesting responses thank you. Giving Aga a call sounds a great idea and I
will do that. The pumped system will need to be turned right down so as not
to exceed the modest heat output capability of the Aga which is oil by the
way. I don't really want to run a 240,000 BTU boiler just to heat a water
cylinder in summer.

This probably wouldn't be too bad if a fast recovery cylinder is used.
These are able to take around 30kW of heat from a boiler, and this is
a 57kW boiler, so the cycling would not be too bad.


The boiler will feed something like 28 radiators so the
prospect of all being shut down sounds unlikely - a no-flow switch closing
down the boiler sounds much more sensible than a room thermostat in one
room.


I am not sure that this would work very well. TRVs tend to reduce
flow rather than cutting off completely unless the radiators are
oversized for the conditions. In effect, this would result in flow
continuing and the boiler cycling. By monitoring the temperature in
the room, the cycling period of the boiler will be much longer because
the room will cool slightly before the room thermostat signals heat
needed again.

It's difficult to say without trying it though. You could start with
the flow switch idea, putting a valve in line with the switch and
another bypassing this valve and the switch so that you can adjust the
flow rate through the switch and hence the sensitivity of the whole
thing.

If it doesn't work and a room stat is needed, you could use a wireless
one if you are bothered about the wiring. Initially this could be
just placed in the room that you think should be the monitored one and
the TRV full opened to disable its operation.



--

..andy

To email, substitute .nospam with .gl

On Sun, 17 Jul 2005 07:18:11 +0000 (UTC), "Hzatph"
wrote:

I don't really want to run a 240,000 BTU boiler just to heat a water
cylinder in summer.

Will you want a 1kW room heater on in the kitchen 24 hours a day in
summer? Only the most extreme Aganoughts leave the things running in
all summer.

--
Peter Parry.
http://www.wpp.ltd.uk/

Peter Parry wrote:

On Sun, 17 Jul 2005 07:18:11 +0000 (UTC), "Hzatph"
wrote:

I don't really want to run a 240,000 BTU boiler just to heat a water
cylinder in summer.

Will you want a 1kW room heater on in the kitchen 24 hours a day in
summer? Only the most extreme Aganoughts leave the things running in
all summer.

Indeed. I love my Rayburn, but it is turned off in the summer. I have an
immersion heater which I can use, and the open fire in the living room
(which is lit on coolish evenings) also heats water via the back boiler.

Sheila

Hzatph wrote:
Interesting responses thank you. Giving Aga a call sounds a great idea and I
will do that. The pumped system will need to be turned right down so as not
to exceed the modest heat output capability of the Aga which is oil by the
way. I don't really want to run a 240,000 BTU boiler just to heat a water
cylinder in summer. The boiler will feed something like 28 radiators so the
prospect of all being shut down sounds unlikely - a no-flow switch closing
down the boiler sounds much more sensible than a room thermostat in one
room.


Well I run a 10KW boiler in sumnmer just to heat the water.

Its very cheap as it comes on about once or twioce a day for 5-10
minutes, and it means I can switch the aga off, which is mandatory in
the summer otherwise it gets insufferably hot..

Will you want a 1kW room heater on in the kitchen 24 hours a day in
summer? Only the most extreme Aganoughts leave the things running in
all summer.

Not at all - I only know one person who switches theirs off! It depends on
the architecture, windows and all sorts of things. the last thing one needs
is a second cooker in the kitchen for when the Aga is off.

Hzatph wrote:

Interesting responses thank you. Giving Aga a call sounds a great idea and
I will do that. The pumped system will need to be turned right down so as
not to exceed the modest heat output capability of the Aga which is oil by
the way. I don't really want to run a 240,000 BTU boiler just to heat a
water cylinder in summer. The boiler will feed something like 28 radiators
so the prospect of all being shut down sounds unlikely - a no-flow switch
closing down the boiler sounds much more sensible than a room thermostat
in one room.

If your Aga heats water for the radiators/HW circuit continuously then the
standard system (as descriped by TNP and Andy H) is not applicable, since
the room stat cannot turn off the heat source (though it could operate the
circulating pump). OTOH if your Aga has a separate heating boiler inside it
(I don't know if Agas have this arrangement but I know that some Aga-like
ranges do) then you should treat it like a normal CH boiler with a room
stat arrangement.

"Hzatph" wrote in message
...
I have two questions that I am sure you can help me with.

1. I have been told that it is a requirement to have a room thermostat on
the heating system even if every radiator has a thermostatic valve. Is
this
the case? It would seem to be a nonsense.

Thermostatic radiator valves are a bodge.
They use a thermostat fitted to attempt to limit the amount of boiler
cycling that is need for the radiator valves to work.

The boiler has no way of knowing if any radiator needs heat ( other than the
one in the room with the thermostat) so expect to waste a lot of energy
compared to a system with individual room stats and motorised valves.


Its odd that the government thinks my 84% efficient boiler with individual
stats and valves is less efficient than a condensing boiler with no proper
control system.
Maybe it needs some new advisors rather than the trade bodies it listens
too.

On Sun, 17 Jul 2005 12:52:36 +0100, Peter Parry
wrote:

On Sun, 17 Jul 2005 07:18:11 +0000 (UTC), "Hzatph"
wrote:

I don't really want to run a 240,000 BTU boiler just to heat a water
cylinder in summer.

Will you want a 1kW room heater on in the kitchen 24 hours a day in
summer? Only the most extreme Aganoughts leave the things running in
all summer.



It's between 500 and 700W steady state because the burner modulates
down.



--

..andy

To email, substitute .nospam with .gl

On Sun, 17 Jul 2005 13:36:53 +0000 (UTC), "Hzatph"
wrote:


Will you want a 1kW room heater on in the kitchen 24 hours a day in
summer? Only the most extreme Aganoughts leave the things running in
all summer.

Not at all - I only know one person who switches theirs off! It depends on
the architecture, windows and all sorts of things. the last thing one needs
is a second cooker in the kitchen for when the Aga is off.

Definitely....



--

..andy

To email, substitute .nospam with .gl

On Sun, 17 Jul 2005 14:00:31 GMT, wrote:

Hzatph wrote:

Interesting responses thank you. Giving Aga a call sounds a great idea and
I will do that. The pumped system will need to be turned right down so as
not to exceed the modest heat output capability of the Aga which is oil by
the way. I don't really want to run a 240,000 BTU boiler just to heat a
water cylinder in summer. The boiler will feed something like 28 radiators
so the prospect of all being shut down sounds unlikely - a no-flow switch
closing down the boiler sounds much more sensible than a room thermostat
in one room.

If your Aga heats water for the radiators/HW circuit continuously then the
standard system (as descriped by TNP and Andy H) is not applicable, since
the room stat cannot turn off the heat source (though it could operate the
circulating pump). OTOH if your Aga has a separate heating boiler inside it
(I don't know if Agas have this arrangement but I know that some Aga-like
ranges do) then you should treat it like a normal CH boiler with a room
stat arrangement.

The Aga has a boiler around the (single) burner, so in effect
transfers heat from the store to the water.

Rayburns have a separate CH/DHW boiler to the cooking piece.



--

..andy

To email, substitute .nospam with .gl

Andy Hall wrote:

On Sun, 17 Jul 2005 13:36:53 +0000 (UTC), "Hzatph"
wrote:


Will you want a 1kW room heater on in the kitchen 24 hours a day in
summer? Only the most extreme Aganoughts leave the things running in
all summer.

Not at all - I only know one person who switches theirs off! It depends on
the architecture, windows and all sorts of things. the last thing one needs
is a second cooker in the kitchen for when the Aga is off.


Definitely....



Why? It comes bolted to the side of the aga

Let's face it, in summer, the last thing you want are roasts and bakes,
which is what the Aga excels at..

We grill and stir fry on the electric part of it in summer.

Or BBQ outisde..

Andy Hall wrote:

On Sun, 17 Jul 2005 14:00:31 GMT, wrote:


Hzatph wrote:


Interesting responses thank you. Giving Aga a call sounds a great idea and
I will do that. The pumped system will need to be turned right down so as
not to exceed the modest heat output capability of the Aga which is oil by
the way. I don't really want to run a 240,000 BTU boiler just to heat a
water cylinder in summer. The boiler will feed something like 28 radiators
so the prospect of all being shut down sounds unlikely - a no-flow switch
closing down the boiler sounds much more sensible than a room thermostat
in one room.

If your Aga heats water for the radiators/HW circuit continuously then the
standard system (as descriped by TNP and Andy H) is not applicable, since
the room stat cannot turn off the heat source (though it could operate the
circulating pump). OTOH if your Aga has a separate heating boiler inside it
(I don't know if Agas have this arrangement but I know that some Aga-like
ranges do) then you should treat it like a normal CH boiler with a room
stat arrangement.


The Aga has a boiler around the (single) burner, so in effect
transfers heat from the store to the water.

Rayburns have a separate CH/DHW boiler to the cooking piece.



Some agas had a separet burner for CH/DHW. But I don't think they do
anymore. They have a fairly poor gravity fed system bolted to the back.

Since its not very flexible, and one needs a separate hot water CH
boiler anyway, I didn't bother, and got the electric companion instead.

"Hzatph" wrote in message
...
Interesting responses thank you. Giving Aga a call sounds a great idea and
I will do that. The pumped system will need to be turned right down so as
not to exceed the modest heat output capability of the Aga which is oil by
the way. I don't really want to run a 240,000 BTU boiler just to heat a
water cylinder in summer. The boiler will feed something like 28 radiators
so the prospect of all being shut down sounds unlikely - a no-flow switch
closing down the boiler sounds much more sensible than a room thermostat
in one room.

Where did the 240,000 BTU boiler come from? What size is your house? or has
an extra nought crept in here?

Where did the 240,000 BTU boiler come from? What size is your house? or
has
an extra nought crept in here?

To answer some confusion, the room stat etc would be on the boiler heating
system - not the Aga.

At present we have two 110,000 boilers on two separate heating circuits and
I want to rationalise with a single circuit and efficient modern boilers -
we have a rambling Victorian place with 28 radiators. Both installers I have
spoken to think we will need a boiler of up to 240,000 BTU capacity.

HTH

"Hzatph" wrote in message
...

Where did the 240,000 BTU boiler come from? What size is your house? or
has
an extra nought crept in here?

To answer some confusion, the room stat etc would be on the boiler heating
system - not the Aga.

At present we have two 110,000 boilers on two separate heating circuits
and I want to rationalise with a single circuit and efficient modern
boilers - we have a rambling Victorian place with 28 radiators. Both
installers I have spoken to think we will need a boiler of up to 240,000
BTU capacity.


Ah so IMHO perhaps what you should think about is a large hot water cylinder
with two indirect coils. One fed from the Aga output and one fed from the
heating system. During especially hot weather an immersion heater might be a
useful extra also. In this way the Aga could heat the water in the cylinder
with its slow but useable heat, The main heating system could under
time/temperature control supply any additional requirement and you have the
option of an immersion if and when needed. If the cylinder is sized
appropriately your Aga should be able to look after all your needs except
under occasional heavy demand periods.
I'm surprised by the loading you suggest for the house even if it is
rambling. Have you done any calcs or tried a heatloss program yourself? I
have done a fair amount of work on a house which did have a 210,000 BTU
boiler installed by others but it was never running for any appreciable
length of time before its stat was satisfied. The house pipework was left
over from a coke boiler and under the ground floor was in 4" Cast iron pipe,
reducing to 3" & 2" branches around the (three) floors and serving big old
cast iron school type rads. The house was bloody huge and could have been a
stately home if out in the country rather than in a town. Draining down was
an all day job as was filling up again so the boiler may have been
deliberately (grossly) oversized simply to speed up the time taken to raise
the water temp from cold to working.
I think the old pile would have benefitted vastly from repiping to seperate
the floors into independent controlled zones with smaller pipe and new rads
to reduce volume and speed up the response times but client (as usual in
these cases) wasn't interested in changing

"John" wrote in message
...

"Hzatph" wrote in message
...

Where did the 240,000 BTU boiler come from? What size is your house? or
has
an extra nought crept in here?

To answer some confusion, the room stat etc would be on the boiler
heating system - not the Aga.

At present we have two 110,000 boilers on two separate heating circuits
and I want to rationalise with a single circuit and efficient modern
boilers - we have a rambling Victorian place with 28 radiators. Both
installers I have spoken to think we will need a boiler of up to 240,000
BTU capacity.


Ah so IMHO perhaps what you should think about is a large hot water
cylinder with two indirect coils. One fed from the Aga output and one fed
from the heating system. During especially hot weather an immersion heater
might be a useful extra also. In this way the Aga could heat the water in
the cylinder with its slow but useable heat, The main heating system could
under time/temperature control supply any additional requirement and you
have the option of an immersion if and when needed. If the cylinder is
sized appropriately your Aga should be able to look after all your needs
except under occasional heavy demand periods.
I'm surprised by the loading you suggest for the house even if it is
rambling. Have you done any calcs or tried a heatloss program yourself? I
have done a fair amount of work on a house which did have a 210,000 BTU
boiler installed by others but it was never running for any appreciable
length of time before its stat was satisfied. The house pipework was left
over from a coke boiler and under the ground floor was in 4" Cast iron
pipe, reducing to 3" & 2" branches around the (three) floors and serving
big old cast iron school type rads. The house was bloody huge and could
have been a stately home if out in the country rather than in a town.
Draining down was an all day job as was filling up again so the boiler may
have been deliberately (grossly) oversized simply to speed up the time
taken to raise the water temp from cold to working.
I think the old pile would have benefitted vastly from repiping to
seperate the floors into independent controlled zones with smaller pipe
and new rads to reduce volume and speed up the response times but client
(as usual in these cases) wasn't interested in changing

John,

You must have been reading my mind - A large cylinder is exactly what I have
in mind so there is lashings of hot water and the Aga can reheat take all
night to reheat it if it needs to. We have a normal size cylinder at the
moment and if we a large amount of water it causes the Aga temperature to
plummet which is annoying at the same time as one is trying to cook.

With regard to heat loss, I do have the Myson program but I have not run it.
We do not have the cast iron pipes you encountered, but one of the boilers
runs 18 radiators and struggles, plus the response time is slow. The other
with only nine and a hot water tank (not all our water is from the Aga!) is
more responsive. I am advised that they may install a smaller jet so the
240,000 BTU unit is throttled back a little - for example the Worcester
Danesmoor Utility 50/70 can be configured from 170-240,000 BTU. I would also
like to create some zones and the heating is configured so some can be
fairly easy way to do

Thanks for your advice - it is much appreciated.

1. I have been told that it is a requirement to have a room thermostat on
the heating system even if every radiator has a thermostatic valve. Is
this
the case? It would seem to be a nonsense.

The requirement is for a "boiler interlock". This means that the boiler
should entirely shut down when there is no call for heat. It isn't allowed
to keep the circulating water hot. This is what would happen if you have
TRVs on every rad and no signal to tell the boiler not to bother.

In 95% of cases, the requirement means that systems are designed to have one
room without a TRV, with a room thermostat in this room. The room thermostat
turns off the boiler completely, which is much more energy efficient.
However, there is another solution suggested in the regs, which is to have a
flow switch on the circuit. This detects when the TRVs are largely closed
and turns the boiler off.

The regs are not prescriptive in any sense. Provided your solution prevents
any gas being burnt at all when the rooms are up to temperature, then it
would be acceptable. The room stat and flow switch solutions are only
suggestions as to how to achieve this.

2. Because of the proposed ground floor location of our new hot water
cylinder our Aga will not be able to heat it on a gravity thermosiphon.

Speak to Aga. It may be that a reliable gravity circulation is required for
safety reasons. This is commonly the case with solid fuel appliances. On
gas/oil, secondary safety systems (i.e. manual reset overheat protection)
may allow fully pumped operation. However, I'm not an expert on Agas, so
don't know what systems they have installed.

Christian.

"Christian McArdle" wrote in message
. net...
1. I have been told that it is a requirement to have a room thermostat
on
the heating system even if every radiator has a thermostatic valve. Is
this
the case? It would seem to be a nonsense.

The requirement is for a "boiler interlock". This means that the boiler
should entirely shut down when there is no call for heat. It isn't allowed
to keep the circulating water hot. This is what would happen if you have
TRVs on every rad and no signal to tell the boiler not to bother.

In 95% of cases, the requirement means that systems are designed to have
one
room without a TRV, with a room thermostat in this room. The room
thermostat
turns off the boiler completely, which is much more energy efficient.
However, there is another solution suggested in the regs, which is to have
a
flow switch on the circuit. This detects when the TRVs are largely closed
and turns the boiler off.

The regs are not prescriptive in any sense. Provided your solution
prevents
any gas being burnt at all when the rooms are up to temperature, then it
would be acceptable. The room stat and flow switch solutions are only
suggestions as to how to achieve this.

2. Because of the proposed ground floor location of our new hot water
cylinder our Aga will not be able to heat it on a gravity thermosiphon.

Speak to Aga. It may be that a reliable gravity circulation is required
for
safety reasons. This is commonly the case with solid fuel appliances. On
gas/oil, secondary safety systems (i.e. manual reset overheat protection)
may allow fully pumped operation. However, I'm not an expert on Agas, so
don't know what systems they have installed.

Christian.


Thank you - that is great advice. In our case a room thermostat solution
would not work as it would be a completely unreliable method of determining
whether there would be a need for heat. Low flow does make sense -
presumably it switches off the boiler but not the pump otherwise there is no
means to generate a flow and switch heat back on when the TRVs open again.

Low flow does make sense - presumably it switches off the boiler but
not the pump otherwise there is no means to generate a flow and
switch heat back on when the TRVs open again.

Yes. However there are some possibilities to avoid the wastage of too much
pump energy. Firstly, run the pump on a clock. Secondly, use a pump like the
Grundfos Alpha, which reduces flow automatically and avoids noise and
excessive electricity consumption. Thirdly, a device that pulses the pump
every ten minutes or so could be good, although I haven't seen an out of the
box solution for this.

Christian.