Faulty TRVs ?

[Rennug]

Hi All,

New to this site and I can't find the answer to my question so apologies if it is actually answered elsewhere.

Anyway, last couple of weeks in Scotland have been a little cold. Turned TRVs on main rads up to max and turned thermostat on boiler up. Noticed that even though the rads in the lounge were hot, they weren't as hot as I would of expected, as the lounge wasn't overly warm. Thought TRV may be stuck a little so turned TRV right down, up, down and back up again. All of a sudden the rad became much hotter. Is this normal ? With the TRV at max and the boiler thermostat almost at max, I would expect the rads to be very hot. Is it normal for the temperature of a rad to rise when the TRV is turned down and up again ? The TRVs are Danfoss (no indication of model) and can't be any more than about 7 or 8 years old.

Thanks in advance to anybody that posts in response.

 

[ChrisR]

You were right, it was stuck!
Worth removing the head from the valve (should be a knurled chrome ring to unscrew, or similar) and pressing the pin down with someting hard (like the top of the head). It should spring freely up and down, something around 4 mm.
Sometimes the expanding wax part in the head packs up, but I haven't known them stick.

 

[Agile]

If TRVs are not operating very often they can become stuck down ( off ).

Sometimes that can be fixed by removing the head and pushing the pin rapidly up and down 20-30 times.

If that does not cure then replacement is the only option.

Sticking TRVs is often a byproduct of a dirty system.

Tony

 

[nickso]

if the trv's are danfoss then the pins can be removed for cleaning. the base of the pin gets crudded up and stops the valve opening fully.

easyish job if you want to try it yourself.