Is our room thermostat working correctly?

[Lottie4]

We moved house in the summer and the heating could only come on if the room thermostat was set to 21c and that's the temp it would warm up to before turning off boiler.

Anyway, have had a new thermostat put in as we like to run the heating on low 17/18. Whether the new one is set to 16, 17 or 18 it continues to warm up to 19/20, at which point some of the radiators then start to cool down as they're obviously registering the room is warm enough - they are set to 2.5 or 3. Boiler continues to run keeping run keeping radiators in two colder rooms on and the one where the thermostat is.As this point we're certainly warm enough so have been switching off heating, usually after 90 mins or so. Should we leave it running and it will then lower and adjust to whatever is set? I was expecting the heating to turn off myself when the desired temperature was reached.

The thermostat is in the hall and I know this is a colder area, but I've put three thermometers in there and they are all confirming the hall is hotter than the temperature set on the thermostat, sometimes by 3 degrees. It's about as far away from front door as can be, not in sun light, on an internal wall, away from heat sources, so there is nothing unusual to interfere.

[PigletJohn]

If you have Thermostatic Radiator Valves, and they work, then you should not be manually turning off the heating. The automatic controls will stop the rooms getting too hot.

If the room where the wall stat is positioned is still too cold, then it is correctly trying to heat that room until it is up to temperature. It is correct for that room to heat up slowest, othewise it would be turning off the heating while other parts of the house were still cold.

There should be no TRV in the room with the wall stat.

It is preferable to have the wall stat in the living room where you spend most of your time, but the "stat in hall" idea was very popular in the 1950's.

[Lottie4]

Thanks for your reply.

Basically, we have set the room thermostat to various temps between 16 and 18c and even though the room where it's based has exceeded that temperature (confirmed by thermometers I've put in that room), the boiler is not turning off. I appreciate dial thermostats can be out a degree or so, but as I say if it's set at 16c, it still carries on heating up to 19/20c and at that point we normally switch it off. If we set it lower than 16c it's not coming on as obviously not cold enough.

[PigletJohn]

it might be that the wall on which it is mounted is still cold, and takes a while to heat up, which will chill the thermostat. Some dial thermostats have an accelerator heater to try to overcome that. Dial stats have quite big hysteresis and do not control temperature very accurately. Try blu-tacking a thermometer to the wall next to the stat.

If you can afford it, I'd swap to a programmable thermostat such as a Honeywell CM907. It has much more precise temperature control, and you can set it for different temperatures according to time of day and day of week. It fits onto the existing wiring for your knob thermostat.

[Lottie4]

Thanks. Have put a thermometer on the wall and it was 2c above set temperature, so something not quite right. I think I'll have to phone the chap who installed it and see if he can replace it, it is a Honeywell but not a programmable one.

[PigletJohn]

is it like this? This one has a Heat Anticipator (a small heating element) but not all do.

See what he would charge to swap it for a Honeywell CM907, which is very good.

[Lottie4]

Thanks. It's actually a Honeywell T6360 (so similar to one you've sent details of). I've spoken to the chap who installed it and he's gone through a number of things with me. Said he's never heard of this before. Anyway, there's something in the thermostat he's going to double check, but he'll bring another thermostat (same model) and replace for free, so we're going with that for now (money is very tight at the moment). However, if problem continues, I'll ask about the Honeywell you suggest.

[PigletJohn]

I expect he will check if it has the accelerator, and if it works.

The other one costs between about £60 and about £100.

[PigletJohn]

it looks like only the 6360B has the accelerator. IMO if the wall is cold that's the one you need.

see table blobs on page 2 www.aee.com.tr/pdf/t6360.pdf

[TheGirlFromIpanema]

My honeywell one does this too Op.

It's like it jumps up 3 or 4 degree's quite quickly and the thermostat hasn't caught up with itself yet.

I've started just knocking it off myself or I find it gets too hot in the evenings. Annoying I agree.

I also thought I could take the thermostat off the wall and move it into the front room at the back of the house where we usually watch TV or whatever in the evevnings.

[PigletJohn]

you can get a wireless stat and carry it round, but I am not keen as they have additional potential points of failure.

[TheGirlFromIpanema]

Mine is wireless PJ - is this a bad thing?

Should I just leave it in the hall where it is then do you think?

[PigletJohn]

You may be perfectly happy with the wireless one. In the main living room is usually the best place, because that's where you want to be most comfortable. If you have TRVs you can adjust all the rooms to be comfortable, with the room stat turning off the boiler once the whole house is warm. The room with the wall stat should have no TRV, or it should be set fully open.

If you have one room that is slowest to heat up, and you can't correct it by balancing, put your wireless stat in there.

[TheGirlFromIpanema]

Aah right, thanks!

I'm not that happy with it as it doesn't turn off quick enough (in the hall - no TVR), like OP's. But if it's ok to move to the main living room thats what I thought I'd try - I'll leavethe TVR fully on though

[TheGirlFromIpanema]

TRV

I take it these are the valves to control them individually though?!

[PigletJohn]

Thermostatic Radiator Valve

[Lottie4]

TheGirlFromIpanema - I'll let you know if a new thermostat solves my problems (might be a few days though as the chap I use is very well thought of, and consequently you have to wait if it's not an emergency!). I've even tried turning down the temperature on the boiler itself a little, so the house doesn't warm up so quick but that hasn't made a difference