galaxi presented the following explanation :
That's just the thing though - the room, in our opinion, has reached
the desired temperature *but* then it seems to drop a bit yet the
radiator in question stubbornly stays off.

There is bound to be some temperature overshoot, until it settles down.


Try using a thermometer in the room - perhaps you have bcome
accustomed to liking the room to be getting constantly warmer (like my
wife).

Possible I guess, I'll have to hunt down a thermometer to check that.

That would be the best way, rather than guessing.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk