room stat

[liljen]

hi guys
please can some one help me i have a potterton boiler and wall stat prt2 when i put the heating on it comes on fine it reaches temp it turns off . however when the temp in the room falls the stat isnt coming back on unless i turn it up more. ive had an enginer round and he said its not a stst its an on off switch i may be female but im not that daft . please if anyone could point me in the right way into solveing this i would be most greatful as im sick of being cold.
thanks

 

[mcmoby69]

could do with more details.
boiler model, type of system how old etc.....

 

[liljen]

Hi
Its a potterton promax HE. Its about 9 years old and the stst is a potterton prt 2 I do believe that the hot water has a seprate way of heating
Thanks

 

[Dan Robinson]

What valves have you got in the airing cupboard?

We may be men, but we're not psychic .

 

[liljen]

Lol. Its has a water tank that's all I could tell you I know the enginer said it was a gravity system that's all I can tell you. Sorry. Could the stat need replacing ?

 

[stem]

It could be the thermostat, particularly if it's a mechanical sort. (I don't know which type the PRT2 is but it's not an old model)

If you are feeling cold, and you turn up the thermostat, hear it click and the heating comes on then, the reason the heating is not on, is as a result of the thermostat.

As a test, try running it a few degrees higher than usual, you may find it a bit too warm before it switches off, but then it shouldn't be too cold before it comes on again, or, hang a thermometer from the thermostat and try different settings for a few hours starting at the lowest first (eg 18 degrees / 20 degrees / 22 degrees) and see if the temperature set on the thermostat is achieved and maintained.

Of course, thermostat location also plays a big part. If the thermostat is in the hallway, then the temperature may be warm enough in there and so the heating stays off. Meanwhile you may be in the lounge where it's cooler. This happens in my home at this time of year. The thermostat is in the hall which stays warmer and so the heating stays off. However the north facing lounge with open fireplace is cooler and so we feel cold. In the winter when the rads are on longer this effect is reversed, probably because the hall has a smaller radiator than the lounge.

The room thermostat is just a switch that turns the heating 'on' or 'off' at the set temperature. However, other things can effect 'how'warm you feel'. What tends to happen at this time of year, because it is not so cold outside, less heat is required to maintain the set air temperature in a room. This means the radiators can go completely cold, so you won't get any radiant heat from them and feel colder. This doesn't happen in the winter when they may never cool down completely before the thermostat turns them back on again. (The principle is the same as the effect of radiant heat from the sun shining directly on you when it pops out from behind a cloud. As a result you feel warmer although the air temperature hasn't changed)