On 12/03/2018 19:31, newshound wrote:
On 12/03/2018 19:22, wrote:
This is slightly difficult to explain. I've just bought a Honeywell
TRV head (TRH4M30WBG) to fit to a valve that previously had another
make of head on it. The thread (30mm) is correct but the central nut
on the valve is smaller than the internal TRV body is designed for, so
the body tends to turn when the head is adjusted. Is there an adapter
available?

Not off the shelf. Whether you could make something out of shim, I
wouldn't like to say. But the odds are that the axial positioning will
also be wrong. You *might* get away with it. How much is your time worth?

If the original valve is old, and/or not Drayton or similar quality I
would not spend long on it.

It's a new Pegler or Honeywell (I think) valve. The house has Evohome
HR92s on every radiator and towel rail but I decided that the airing
cupboard would be better with a regular "old fashioned" TRV and didn't
think to check what stops a TRV body from turning. I think the axial
stroke is OK so, if necessary, I'll have to make a widget.