With the warm weather with us at last, I decided to turn the central heating
off, so I switched the Danfoss TP5 Digital Thermostat to Frost only. This
didn't make any difference and the heating kept on coming on. Next I turned
the Danfoss Central Heating / Hot Water Controller off, so it should have
only provided hot water, still got hot radiators. Next I switched the Boiler
to just hot water and no central heating, still got hot radiators.

The oil fired boiler (Worcester I think) was installed about 15 months ago
to replace a gas system. I moved into the house about 4 months ago. There is
now no hot water cylinder as the boiler is meant to provide hot water
direct. It does this but will only fill a bath with hot water if the tap is
running slowly.

Any ideas of what may be going on to allow the rads to keep getting hot,
with everything switched off, would be gratefully received.

Julian Ashcroft
Isle of Man

Any ideas of what may be going on to allow the rads
to keep getting hot, with everything switched off,
would be gratefully received.

Dodgy zone valve?

Alternatively, and I don't know the design of the boiler in question, the
radiator circuit may be pump controlled rather than valve controlled. If so,
there might be some parasitic gravity circulation, although you would only
expect the radiators to warm up when the hot water was actually being run
then.

If the design is actually a small heat bank or similar, this may also
gravity circulate and even cause boiler firing on its own accord.

It may be an idea to post the model of the boiler to determine how its
control systems are likely to work.

Christian.

"Julian Ashcroft" wrote in message
...
With the warm weather with us at last, I decided to turn the central
heating
off, so I switched the Danfoss TP5 Digital Thermostat to Frost only. This
didn't make any difference and the heating kept on coming on. Next I
turned
the Danfoss Central Heating / Hot Water Controller off, so it should have
only provided hot water, still got hot radiators. Next I switched the
Boiler
to just hot water and no central heating, still got hot radiators.

The oil fired boiler (Worcester I think) was installed about 15 months ago
to replace a gas system. I moved into the house about 4 months ago. There
is
now no hot water cylinder as the boiler is meant to provide hot water
direct. It does this but will only fill a bath with hot water if the tap
is
running slowly.

Any ideas of what may be going on to allow the rads to keep getting hot,
with everything switched off, would be gratefully received.


I'm guessing that you have a Heatslave Combi from what you have said so far.
IIRC this has a diverter valve to switch the boiler output to radiators when
required and the hot water demand is not overriding it. The hot water to the
bath presumably starts off OK but runs out of steam before the bath is full?
It is possible that the diverter on your boiler is a Danfoss with a white
plastic motor head and if the motor had failed and someone put the manual
lever across to give heat to the rads this will remain in the shared
position until it is restored or the fault rectified. The symptoms will be
as you describe i.e. heating on all the time the boiler is on heat or hot
water duty and poor hot water performance.
Its also possible to achieve the same symptoms with a stuck diverter or even
"other causes" but try these first. If no good please come back for more g

Thanks for that. Time to give the heating Engineers a call.

Julian Ashcroft