On 15/02/2016 07:45, harry wrote:
On Sunday, 14 February 2016 18:38:04 UTC, Justin C wrote:
I'd like to avoid calling the plumbers back if I can.

Last week we had two stuck-shut TRVs replaced, the new ones are
marked Bulldog gen2. We were looking forward to being warm again
but alas, twas not to be. I thought that maybe the rad needed
flushing, so did that myself yesterday - it did need doing but
didn't fix the issue.

I took the head off the TRV and the radiator was too hot to touch
within a few minutes - result! But then the TRV cut flow before
the room got up to a habitable temperature. I compared the head
with the other one they fitted and the plunger was much more
proud, I swapped them over (the other is in a room infrequently
used and we don't mind it being chilly). That'll do it I thought,
except no... within a short time the heat from the rad had
expanded the (whatever it that makes these work) and we were in
the same situation.

So, even at 'full-open' these TRVs cut flow before the room is
warm, we're constantly chilly. Can these be adjusted somehow (I
can't see it if they can - short of taking a dremel to the plunger
in the head). Or do I need to call the plumbers back in?

If I barely put the head on - so the fixing ring threads only just
grip - 1/8 to 1/4 turn - we have the kind of temperature we want,
but that's not right.

Suggestions gratefully received.



Justin.

That is the problem with TRVs.
They are influenced by the radiator/nearby pipework as much/more than the room temperature.
It's why some are installed horizontally. (To get the head further away from the radiator)
Or sometimes even in outlet (cooler part) of the radiator/pipes)


TRVs do have their limitations - but there's something definitely wrong
in the OP's case. I suspect that the heads are the wrong ones for the
valves.
--
Cheers,
Roger
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