Room Stat for boiler?

AnotherMakes3

I just read on another thread that room stats should be fitted as standard. Can anyone please tell me when this came into force?

We got a new boiler fitted back in 2006 and we have thermostat valves on all the radiators in each room. Do we still need a room stat?

I cant help but think we should still have something that stops the house from getting too hot. We have an ideal isar a+ boiler and i have the thermostat on the front sitting at half way.

ariba10

We have TRVs on all but one of our radiators, but no room stat.

Personally I do not see what use they are in those circumstances.

AnotherMakes3

Thanks. Do the TRV's tell the boiler to stop firing though? I am a bit clueless on this!

closed

if they are set properly, they will close off when the room gets to temp, which will mean the boiler will fire less. If you have them set to max, they do nothing

penrhyn

If you rely totally on TRV's then the pump will never switch off during the heating period, there is usually one radiator usually in the bathroom without a TRV.
Personally I prefer to have a programmable room stat in the main living area.

Cardew

I actually have a room stat and TRVs on all radiators and towel rail(with an Automatic Bypass Valve(ABV) it is not necessary to have a one without a TRV)

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

I appreciate that it is not perfect in that the pump is running when the CH is on; however a stat in a cool hall is not ideal to determine temperature of other rooms. Similarly if I move the stat into a reception room, why should that determine if heating is off in other rooms?

Don't forget that the boiler stops firing when the water temperature reaches the set level.

ariba10

If you have a room stat, when it is satisfied it will shut all the heating down.

Making the TRVs useless.

penrhyn

Tend to agree about them being useless, or am I missing the irony.
At mothers we had the programmable room stat in the lounge, which was the warmest room, and the TRVs in the bedrooms set to regulate at a lower temperature.

Pincher

At the boiler end, there is a wire called the demand line. You put 230V on it, and the boiler fires up.

The TRVs has no such connection to the boiler, they just switch off the radiator when the room it's in gets warm.

The programmer, hot water cylinder thermostat and room thermostat(s) combine to turn the demand line on and off according to your settings.

So when all the radiators are closed, the boiler can still be on, the water in the heat exchanger gets hotter and hotter, going round the short circuit through the bypass valve. The boiler sensor tells it to turn down the gas, and if it gets too hot, the boiler will shutdown, disregarding the demand line.

If the sensor fails, and the water gets superheated, it will spurt out of the pressure relief valve (8 bars), like a steam engine.

I myself always have a non-TRV radiator that I make sure is never closed, after a flow pipe rupture due to a failed flow sensor about 20 years ago. Fortunately nobody was standing in front of the pipe at the time. The bang was terrifying.

These days, of course, plumbers always fit valves the right way round, and sensors hardly ever fail.