On 17/12/2011 16:39, 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?

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

Even when one circuit is shut off water can conduct heat just because
it's water.
When our shop became a 2nd zone off the heating circuit in the flat
above they plumbed the return from the shop into the closest return from
the flat. When shop zone was off by zone valve the Myson hi-line shop
fan heater would still fire up sporadically by simple conduction of
water in the Flat's return line raising temp high enough to cause
internal thermostatic fan to trigger.

Plumber had to come back an run a new return line for shop zone right
back to boiler to sort the problem.

Perhaps balancing the radiators accurately to significantly reduce the
amount of water that has access to conduct heat back in from the return
might help rather than the usual idea of trying to let TRV's sort
everything out?

Cheers
Pete

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