We seem to have a little problem.

CH is gas boiler (Potterton Netaheat), programmer has separately
selectable HW and CH times, and they are independent of each other.
System has pump, cylinder etc. remote from boiler, thermostat in
hallway.

Problem: the CH comes on even if thermostat is set to minimum. I then
turned the CH off completely at the programmer (in other words,
disabling the timer) and STILL the rads get hot. However, if I turn the
HW off at the programmer too, the rads cool down.

Now, this isn't my area at all, but I would suspect either the
programmer or the electrically operated valve (presumably a 3-way one
since we have independent control of CH and HW). I can't actually look
at the valve right now because it's in a room where SWMBO is asleep
after a bad night!

Are my assumptions correct? And is the valve the most likely culprit? If
I read the FAQ right, the most common failure mode is a burn out coil
leading to CH on all the time - is this correct?

--
Bob Eager
begin a new life...dump Windows!