In message , Gareth
writes
"thirty-six" wrote in message
...

On Dec 17, 4:39 pm, "Gareth" wrote:
I posted a while ago about radiators heating up when the central
heating is
turned off but just the hot water is turned on (conventional boiler).

I've realised that the radiators are also heating up - almost all of
them -
when their thermostatic valve is switched off.

It seems too much of a coincidence that every thermostatic valve -
about 8
of them - could be faulty.

Does this sound like a reverse circulation problem?

Sounds like you are without a bypass loop in your heating circuit.
Thermostatic radiator control valves do not necessarily have a
positive shut-off positon and those will lift given sufficient
pressure from the circulating pump.


If so is there a way of fixing it without causing too much disturbance to
pipe work?

Take the conrol head off the rad nearest the boiler, so it's on all
the time, and control its actual output with a towel.

Thanks guys for the replies - much appreciated.

This last comment about keeping the rad nearest the boiler on all the
time has made me remember something I had forgot.

When we moved in the previous occupant had left an instruction sheet
with the boiler saying one radiator must be left on full all the time
(the one in the bathroom nearest to the boiler). Why would this be?

You've said the same thing. Does opening that radiator reduce the
pressure flowing in to the other radiators?
AIUI it is normal to have one radiator without a TRV, the one in the
room which contains the room thermostat.
However the OPs problem is that radiators are still heating up even when
the heating is switched off but the hot water is on. This suggests as
someone has already said that a motorised valve is not switching
properly.
--
hugh