uncontrollable radiator

[yewturner]

a weird one. any help greatly appreciated.
lounge radiator with thrmostatic valve, logburner in same room and i can't turn the rad valve off/control it when the burner lit. the rad ends up very hot. I have swapped the the valve for another and still no luck, it works ok when burner is not lit. the other isolation valve on radiator is open and appears to work. cheers

 

[stem]

Here are a couple of things to consider.

1. Log burners emit a lot of heat by radiation. Radiation does not heat the air directly, but rather solid things such as people that are in its path. The sun is similar. On a hot day if you are in direct sunlight, it will feel cooler when a cloud obscures the sun, or you move into the shade. The air temperature doesn't change, but you feel cooler because you are shielded from the sun's radiation.

In your home, your body will be heated by radiation from the log burner and you may feel hot, yet the air temperature could still be low enough to for the TRV to keep the radiator on.

2. Radiator thermostats shut down to reduce and eventually stop the flow of hot water into the radiator, however, it can take a long time for the radiator to cool, so the TRV can be off for a considerable time before the radiator cools.

 

[yewturner]

thanks for the reply
since i posted the question i have tried several things

i turned the thermostat off before i lit the burner and it still reached a temperature that was uncomfortable to touch when the boiler was on.

i have also shielded the thermostat from the lounge door - it may have been effected by a draft (a bit far fetched i know but i am trying everything i can think of

in desperation i have even checked the hot water feed was connected to the thermostat. (yes it was, so back to the start)

my next step is going to be to replace the whole thermostat valve but i will have to wait for a warmish day or i will get so stern looks of the rest of the family before i drain the system.

once again thanks for replying.

 

[Hugh Jaleak]

Did you just swap the head of the valve or the entire valve? Some Thermostatic valves are 'one way', if fitted the wrong way round they dont work too well. Check arrows on valve body, water must flow in direction of the arrows.

If replacing look for a 'bi-directional' valve, can be fitted on flow or return pipe.

 

[yewturner]

yes i did just swap the head of the valve (with a similar valve in the house)

i will look for a 'bi-directional' valve. cheers