Thermostats and TRVs - help! (Non smart)

caroline1973lefty

I’d like to understand my heating controls better. I’ve got a thermostat in the hall and TRVs on all radiators throughout flat. I tend to have the hall thermostat at 20 (or off). If I have the TRVs in other rooms higher, ie IV or V, which would prevail? Would the rooms with those settings keep heating up, even if the main flat thermostat was 20? (Have I been doing it all wrong?! I never really understood the TRV settings!)

Also am I correct in understanding I should have the TRV on the radiator in the hall (ie, near the thermostat) set to V (max)?

and is it better to have the flat thermostat in the living room ( where i spend most time)? I would have thought so, I don’t really care if the hall is heated. But a heating engineer told me it’s good to have the themostat in the coldest area like a hall but this confuses me.

grumbler

If heating is on AND the temperature in the hall is below 20, the boiler heats the water that is pumped though all radiators.

Each TVR controls the flow through a particular radiator and thus its temperature. The hotter it gets in the room, the lower the flow.

Ideally one radiator has to be without a TVR, so the the flow through the CH wouldn't be able to stop completely.  If all radiators have TVRs, then yes, at least one must be set to maximum.

Yes, it's better to have the thermostat in the place where you spend  most time. Or you can have a wireless portable thermostat.

FreeBear

The heating will be controlled entirely by the thermostat. So if the temperature in the hall reaches 20°C, the boiler will switch off regardless of where the TRV in the other rooms are set to.

Conventional wisdom says that the radiator nearest the thermostat is not fitted with a TRV (or if it is, set it to MAX). No reason why you couldn't have a wireless thermostat that you move from room to room - Just watch that the TRV isn't set too low though.

NSG666

Are you having any specific issues? If not and the system is reaching your desired temperatures then leave it alone.

For info though, the radiator in the room where the thermostat is shouldn't have a trv fitted to it - if it has then set it to maximum and never turn it down or it can create problems including banging noises.
I used to be of the opinion that the thermostat would be better in the main living area until I tried it and found, that for me in my home it did not work so I put it back in the hall - you and others might find it's better or worse.
If the trvs are bog standard then the only time they can do anything is when the timer and thermostat or programable thermostat turn the boiler on.

victor2

I have a wireless thermostat, but have fixed it to the wall in the hallway, where the old thermostat used to be.

Most of the radiators in the house have TRVs on them, but the hallway does not, and is permanently on. Just work out a balance you're happy with for the hallway temperature that allows the other radiators to be controlled by their individual TRVs. It might be warmer than you need in the hallway, as once that reaches the set temperature, all other radiators are effectively switched off.

ashe

The key thing to know with TRV's is it's the room temp not the rad temp. Here is a rough guide:

Numbers & temperatures

The numbers on the valve roughly correlate to the room temperatures below. When the room drops below these temperatures, the TRV will allow hot water to flow into the radiator:

• 0 = Off
• * = 7°C
• 1 = 10°C
• 2 = 15°C
• 3 = 20°C
• 4 = 25°C
• 5 = 30°C

Thermostat is king, but rads can turn off/on while thermostat is on depending on settings by stopping water flow. There are some smart ones that can call for heat on their own but thats a whole other game.

Bendy_House

Interesting that more than one person above has found that the 'stat is turning their heating off before they want it to. The answer to that is to slightly tweak down the rad in the room with the stat, so it heats up less - this will then allow the other rooms time to heat up properly.

If you don't have a room stat set up properly, ie to turn the boiler off at times when it has met demand, then you don't have an effective 'interlock', are non-compliant (who cares...), but are also wasting energy, with the boiler running for too long.

Caroline, it's a weird one to first get your head around. I think the idea is that the room stat is positioned in a room which is quite 'stable' in temp, and is representative of the whole house's demand; the hallway would usually be kept slightly cooler than living spaces, but it would still be kept at that temp - ie stable. I guess the hallway was traditionally chosen as it ain't a bedroom (which most folk would have cool during the day and eve), and is not a sitting room (which many folk would also be heating via fires and stuff). If you can imagine placing the 'stat in either of these rooms - in a cold bedroom, it would tell the boiler to keep running, so the rest of the house would have unnecessary heating. If placed in a secondary-heated living room, it would tell the boiler "Phew - it's too hot, man - turn off", and the rest of the house would then get cold.

It becomes a balancing act. The idea is that the hallway should be able to get to 18oC at roughly the same speed as the living areas get to 21+oC. You control the heating level in the living areas by setting their TRVs in there to 3-ish or a tad above, and you then adjust the manual control valve on the hallway rad (this should NOT be a TRV) to enable the hallway to heat up to 18oC at the same time as the sitting room hits 21oC, or fractionally slower.

If, when the boiler turns on, the hallway reaches 18oC (which will then turn off the 'stat) before the sitting room reaches the required temp (say 21oC), then it should be clear that the sitting room just ain't going to heat up properly before the stat tells the boiler to go back off. The answer is NOT to turn the sitting room TRV up higher, as this will make no difference - it'll still heat up at the same speed as before. The answer is actually to turn the hallway rad down a wee tweak so it takes longer to heat to 18oC, and that should now allow the living room more time to get to its required ~21oC at roughly the same time. At this point - hallway at 18, sitting at 21 - the boiler should turn off for a while. When the hallway temp drops a bit, the boiler comes back on.

You then check and play with these settings. If you find the boiler is still being turned off too quickly or too often by the hallway 'stat, then turn the rad in the hallway down a teeny bit more (the control will be very sensitive at near 'close' position, each part-turn likely having a strong effect.)

For the bedrooms and the rest of the house, you just run around turning their TRVs up and down as required - ie beds on a half-hour or so before bedtime.

Personally, I prefer to have my room stat in my living area as - quite simply - that's the most important room, and the one which I want to control the temp properly! Over winter, tho', when the sitting room got up to temp and turned off the boiler, this meant that the rest of the house cooled off, sometimes more than I wanted (the kids moaned as they practically lived in their bedrooms...), so I'd have to turn off a sitting room rad (to stop it becoming too warm) and turn up the stat to heat the rest of the house. In such a case, then, having the 'stat in the hall would have made more sense - the sitting room would not have been dictating the rest of the house, but the constant, 'stable' hallway would have. And my kids would still be talking to me...