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Central Heating

Radiator trv on full or it wont come on

We recently had new radiators put on but kept all the old angle valves lockshields and just changed the radiator and thermostatic valves on the radiator. The radiators don't warm up at all just the pipes get hot but not the rad unless we have it on 5-6 any lower and the radiator just stays cold. also the room thermostat in hall (hall rad has no trv) wont go off less than 10 and you only hear the heating kick in if that put upto 25+ so essentially we can only have the house boiling or freezing no in-between?

extra info: its a drayton so deffo not a cheapie we just screwed it on the old angled valve rather than putting on new one supplied for ease n quickness. also how can it be on wrong side when only one side has a pin? thats the side its on top of the pin side. the other side which has nothing over just a little plastic cap I think its called a lockshield can only be twisted with a mole grip. obviously i dont really have a clue but any more help or detail would be great.

2 Answers from MyBuilder Heating Engineers

Sounds like you have the valve on the wrong side, it must be put on the flow side of the radiator.


Answered 30th Jan 2015


Cheap TRVs can be troublesome with regard to flow regulation. Unfortunately I would be looking at replacing the TRV and valves at the same time. A good TRV can be picked up for around £15. I have come across some that seem to simply be on or off as you have described. Also sounds like an issue with the thermostat. Depending on the type of thermostat you are using but even for an old thermostat I would say the wax capsule has lost its calibration. A good room thermostat and quality TRVs should see to these issues.

The radiator has a flow and return. It is possible that the valve is on the return rather than flow. However when replacing TRV heads only you run the risk of issues. A TRV angled body and the head are calibrated to work together on a set spring compression. Using a new head on an old valve (possibly with. Weaker or seized spring) could cause the issue you are describing.


Answered 1st Feb 2015

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