thermostatic valves

cajef

helaus wrote: »

because the rads have got to required heat - the valve closes and therefore no more hot water is required - so boiler switches off

But the pump is still running, pumping water round via a bypass loop, when the water cools down the boiler fires up again even though you do not need heat as the radiator valves have closed, so you are wasting electricity and fuel.

helaus wrote: »

its not possible to have room thermostats and radiator thermostats - either the rad valves turn off the boiler or room stat - they would just be a conflict with such thermostats

Of course you can have thermostatic radiator valves and a room thermostat, that is the recommended system nowadays which is why the energy report recommends you have one fitted, you use a combination of the two to control the boiler, the pump and overall temperature.

Cardew

However I never use my room stat; it is situated in a large hall with stairs leading off. I just turn it up to 28C and the temperature of each room is controlled by the TRV and obviously never reach 28C

bob_a_builder wrote: »

I have always liked the sound of this approach for a more even consistent temp around the house, but fear (possibly incorrectly) that the system would cost quite a bit more to run that way, but have always meant to have an experiment with that way of operating ( i have all the TRVs fitted, just never got round to it)
pumps probably not rated for near continues operation though, but easy enough to replace

Well I have just replaced my second pump in over 22 years, so if they average 11 years life with far more running we can't complain.

It is quite correct that the way I run my system causes the pump to run longer and the boiler to fire up more often.

However where does the heat(energy) from that firing up of the boiler(as the water cools), and pump running, go other than into the house?

I do it for reasons of convenience as I have a largish house and I don't want any one location(where the stat is situated) determining the heating in other locations.

victor2

Cardew wrote: »

It is quite correct that the way I run my system causes the pump to run longer and the boiler to fire up more often.

However where does the heat(energy) from that firing up of the boiler(as the water cools), and pump running, go other than into the house?

I do it for reasons of convenience as I have a largish house and I don't want any one location(where the stat is situated) determining the heating in other locations.

The unrequired hot water presumably goes round the pipework, exchanging heat with the brickwork, ground or wherever the pipe travels, certainly not the radiators.
Agreed it is for convenience, but I would see the main thermostat as being a "master" control, set accordingly so that it only switches the pump off when the house is warm enough not to require any heating. If a programmable thermostat then it's much more flexible - you could have your heating on all night but with the thermostat set low when you are in bed, so that regardless of what the TRVs demand, the radiators will only get hot water if the thermostat temperature drops below its night setting.

Cardew

victor2 wrote: »

The unrequired hot water presumably goes round the pipework, exchanging heat with the brickwork, ground or wherever the pipe travels, certainly not the radiators.
Agreed it is for convenience, but I would see the main thermostat as being a "master" control, set accordingly so that it only switches the pump off when the house is warm enough not to require any heating. If a programmable thermostat then it's much more flexible - you could have your heating on all night but with the thermostat set low when you are in bed, so that regardless of what the TRVs demand, the radiators will only get hot water if the thermostat temperature drops below its night setting.

A couple of points.

Firstly the heat from any pipes will go into the 'fabric' of the house so is not 'wasted' i.e. if they dissipate xkWh(BTu) that is still xkWh that the radiators will not have to eventually provide.

As said previously, my wall stat is in a large hall with a staircase leading upstairs. Although it has radiators, they are rarely on as it is pointless heating such a large area.

If I moved the stat to a reception room, then that room would effectively control the heat in other rooms. If that room is not being used, if I turn the stat down it turns off the pump and the other rooms get no heat. If I turned down the TRVs when the room was not occupied(which I do currently) then we are back to square one, with the pump running all the time.

I am certainly not arguing that my way of operating is the most efficient, it clearly isn't. My gut feeling though is that it doesn't make a huge difference.

reeac

Cardew wrote: »

A couple of points.


As said previously, my wall stat is in a large hall with a staircase leading upstairs. Although it has radiators, they are rarely on as it is pointless heating such a large area.


I am certainly not arguing that my way of operating is the most efficient, it clearly isn't. My gut feeling though is that it doesn't make a huge difference.

Why not set the wall thermostat at, say, 15C and have all the relevant TRV s open? That offset will compensate for the naturally cooler hall.

Cardew

reeac wrote: »

Why not set the wall thermostat at, say, 15C and have all the relevant TRV s open? That offset will compensate for the naturally cooler hall.

Because if the hall reaches 15C, the pump will stop and there is no heating in the other rooms.

What is the point of the hall temperature dictating if there is to be heat in the other rooms?

If I set it to, say, 18C and the hall doesn't reach 18C then we have exactly the same situation as if it were set to 28C.

It is difficult to quantify how much extra gas 'my' method will use, but given the heat from pipes etc is not wasted, I suspect it isn't a great deal.

Don't forget there are many older CH systems without any form of wall stat to control the pump.

There also was a discussion on this subject on a forum, with several heating engineers contributing, complaining about the compromise needed in siting and using a wall stat and a couple use exactly the same method as myself.

However to re-iterate I am not recommending this course of action.

reeac

Personally, Ive always been doubtful about the efficacy of a TRV in controlling the temperature of a room. The sensor is so close to the source of heat [the radiator surface] that the valve will be influenced by the temperature of the radiator rather than that of the room. I agree that there will be a correlation between the two temperatures but it's not a good way to control things. It's all a bit indirect like controlling your cars speed by reference to the instantaneous mpg figure displayed by the fuel computer ...er. .. maybe not THAT bad.

Pincher

You can put in a thermostat per room, and demand heat from the boiler if any of the rooms need more heat. It's just more expensive, more effort and the one room thermostat with TRVs is more cost effective.

With under floor heating, the time lag between adding heat and temperature rise is so long, that one wall thermostat per room is almost unnecessary. It is much simpler to check the temperature at the manifold, and maintain the return flow temperature.

Cardew

reeac wrote: »

Personally, Ive always been doubtful about the efficacy of a TRV in controlling the temperature of a room. The sensor is so close to the source of heat [the radiator surface] that the valve will be influenced by the temperature of the radiator rather than that of the room.

Logic would support your contention, but in my experience they do work effectively.

I have a fairly large reception room(approx 36' x15') where because of the layout with doors etc, both radiators and TRVs are behind settees with only a couple of inches between them. Logic would suggest this would render the TRVs ineffective.

Using a thermometer in the middle of the room with both set to 20C the room remains close to that temperature - with less than 1C variation.

I suspect the convection in rooms is better than we think!!!

mike323

Hi. Not sure if this the right place to post to, but here goes anyway.
I very recently had a new boiler installed by British Gas, Now the thing is that the radiators are old though they were flushed and they sure pump out the heat, but what i am bothered about is that a friend of mine who is a fully qualified plumber has told me that they should have fitted thermostats on all but one of my 7 radiators and that they have broken building regs in not fitting them, so (A) what do i do, and (B) is my home safe.