Eternally Hot Radiators

Our Glow=worm 80B heats the radiators continually even when the Honeywell controller has central heating to off.
Is this most likely a controller/boiler or
valve problem? hot water seems under control.
There is a Grundfos circulator where is that
likely to be? I am trying to build up a map
of system before attempting anything.
Oh yes the only way to stop the radiators is
to set the boiler thermostat to 0.
Any assistance most appreciated.

Probably a valve.

are you on a y plan ie 1 x 3 way valve or an s plan 2 x 2 way valves?

Hi oilski,oilman,
Thanks for your posts.
Finally located the pump and valves under the bathroom floor.
I suppose they keep the bathroom warm but is the pump
meant to be horizontal?
It seems to be S plan - 1 valve for hot water tank, and
1 valve for ch. Each valve has 5 control wires - Is there
any way of debugging these? Only the brown wire connection
is different (5 or.
Each valve has a small lever on it side which appears to
move on the hw valve but not on the ch valve. I'm looking
at the Sundial "S" plan wiring diagram but there are no signal or
pattern diagrams.
Any acid test for the CH valve would be most appreciated.

The pump can go any way as long as the shaft is horizontal. This is important or the pump will wear out in about 16.88 seconds.

What make are the valves?

There's not much needed to establish their correct operation.

Turn the CH and HW off, then see if there's a spring loaded resistance on the CH valve. There probably won't be.

Remove the head from valve body, and operate the lever again and see if there's resistance. If there is, turn on the CH and you should see the lever move to its open position.

This indicates the valve itself is stuck. Get a small adjustable spanner and give the spindle a tweak.

If it's not the spindle, Replace the head. You might be able to just replace the motor, but only if the head is not very worn, otherwise change it, they are not well built.