Thermostats with TRVs

[croydoncorgi]

Because the roomstat is set to (say) 18 it will switch off the whole CH system when the temperature reaches 18. By setting the nearby TRV just below 18 (by turning it down in small steps until the room warms up slowly enough) the roomstat will stay on long enough for the rest of the building to heat up under the control of the other TRVs).

The key problem is when the roomstat really is in the warmest room in the house: that is, not only 'warm' but also slow to cool when the roomstat switches off the heating. Then, by the time the roomstat calls for heat again, other parts of the house will be overly cold. I sort-of assumed that the builders in this case could not REALLY have been so dumb as to put the roomstat in such a place. If they did, and other parts of the building show big swings of temperature, then the only thing to do is move the roomstat. The presence or absence of a TRV in the same room is irrelevant.

Just because a room is 'warm' relative to others does not necessarily mean that the roomstat will not work in it. For example, the original postings described an upstairs room with two rads - I'm getting the impression of the living room of a town house - and the roomstat. OK - the roomstat will presumably be set to (say) 20. Turn down the TRVs on both rads a bit and delay the switch-off of the roomstat. Rad downstairs in kitchen (with TRV wide open) keeps going and warms up kitchen and corridor. Warm air rises up the stairs and helps warm the living room, at which point the roomstat switches off.

But if the kitchen and corridor downstairs are cold because the (single) rad in the kitchen is actually undersized - that's a whole different and much more expensive problem. That can easily be checked by just doing the sums.

 

[Multiplex]

Well I guess I should post about the practicalities of having a roomstat in the warmest room in the house. First this is a townhouse with three floors, and the living room is on the middle floor. The living room is not huge, but still has two radiators. It also has doors that are kept closed.

When we moved in we put the roomstat to 22 and found the kitchen was stone cold because it never had a chance to heat up. The kitchen has a concrete floor and has twice the windows of the living room, yet only one radiator. To get the kitchen to heat up quickly we had to open the window in the living room to get cold air in.

Now we've balanced it by turning the TRVs down in the living room to 2 or 3 and the kitchen rad is on MAX. The roomstat is on 21.

The problem is the kitchen gets colder quicker than the living room. So the living room gets to 21, and maintains that heat and then even gets a bit hotter with the TV and computer being on. So no call for heat and the kitchen gets cold again.

So because the living room is very well insulated and the kitchen isn't it's pretty difficult to balance.

The hallway off the kitchen has a small rad without a TRV and would be perfect location for the roomstat.

Thanks for all the replies. Unfortunately I don't know where blahblah got his building regs quote from but part L regs on the odpm website don't spell it out quite so clearly. And yes all I want is a stick to beat this builder with...!

Simon

 

[blahblah]

From The Domestic Heating and Hot Water Guide to the Building Regulation 2002 Part L1. The Regs themselves don't (I believe) say not to put them in the same room - nor do they tell you not to slam your bolx in a door. Its assumed you would know better. But they follow up with the guides because people show they don't know better!
Disconnect roomstat and invest in a wireless one in the hall. Should solve all.

 

[kevplumb]

nor do they tell you not to slam your bolx in a door

thats where i went wrong then

 

[blahblah]

Do you type in a really high voice then?

 

[kevplumb]

yeeeeees

 

[croydoncorgi]

Sounds to me like the builder DID get the CH design wrong, with undersized rads downstairs, so the siting of the thermostat is the lesser problem!

Putting a radio stat in the downstairs corridor (not too close to the rad there!) is probably the cheapest solution, rather than putting in bigger rads downstairs! Tell him that and he'll probably see sense without the need to quote Regs.