On Mon, 9 Aug 2004 10:09:43 UTC, Andy Hall wrote:

On 9 Aug 2004 08:29:29 GMT, "Bob Eager" wrote:
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).

Either a burnt out motor or sticky valve or gooed up with grot.

You can take the head off of the valve and check whether or not the
motor runs (you can buy the motors separately). Then test the valve
base, trying to turn it. If stiff, your culprit is there.
It could be a microswitch in the valve head, but less likely. That
needs a test meter to check out.

Hmm. Further examination indicates that, even with the CH part turned
off at the programmer, water flows out of both ports of the 3 way valve.
As might be expected given the symptoms.

HOWEVER....the CH pump is also running....! Surely that would indicate a
fault in the control system rather than the valve - or have I missed
something?
--
Bob Eager
begin a new life...dump Windows!