In message ,
Tricky Dicky writes
I have the following TRV installed on our lounge radiator and I am
experiencing some problems with it and would appreciate any advice
before I contact the manufacturer.

https://www.screwfix.com/p/white-ang...v-15mm-x/73649

We control the temperature using Hive which is normally situated in the
lounge but can be moved to our other reception room depending which we
are using most and require accurate temperature control. When the Hive
thermostat is situated in the lounge the TRV is set to its highest
setting - 5 (27-29C) so as not to conflict with Hive. When Hive is in
the other reception room I rely on the TRV to keep the temp in the
lounge at the required level by setting it to the correct temp setting.

Today I found the the valve shut tight and Hive reporting the room temp
at least 2 degrees below set temp and firing up the boiler to
compensate. To my mind the valve should never even be shutting
considering the vast difference between temp settings on the TRV and
Hive? Do you think the head is faulty, do they have a long hysteresis?
This is a replacement for the previous head which appeared stuck in the
shut position. With the head removed everything is quite normal the
valve itself opens and shuts easily and does not appear faulty.

I don't have anything that young but all my problems are due to the
valve pin sticking in the closed position.
Usually, scraping the lime scale off, lubricating with plumbers grease
and some vigorous push/pull activity with a pair of pliers cures the
issue for another 12 months.

--
Tim Lamb