Conventional pumped system. Hot water OK but no central heating

tired_dad

Have a conventional boiler in utility. Hot water storage upstairs, CWS in loft. Pumped system with a valve ( not sure about the 2 or 3 way side of things, but there are 3 pipes going into the valve).


There is a old programmer ( slider for hot water and heating with options for "off, once, twice, continuous").


Problem: hot water working with no problems. Boiler fires up no problem. However, no heating. The programmer lights up OK as if it's functioning. The CH pump remains silent and the boiler does not fire up).

It's a grundflos pump.

Would value advice ESP at making a diagnosis.

TIA

Nilrem

Is there a room thermostat for the heating?

If not I suspect the programmer has partially died given that the wiring to the boiler is obviously fine (otherwise no hot water).

If there is a thermostat that may have died, or a cable is loose between it and the programmer.

the good news is, that a new programmer is only about £30-50 so if it is that it's a fairly cheap fix.

tired_dad

No room thermostat, just an old dial on the boiler itself.

There is a long probe that is sited at the top of the firing chamber. It fits into a hole into the chamber. Not sure what that is

gas4you

Do the radiators get hot if the water is on?

If not, sounds like the actuator head of the three way valve has broken.

Most can have the head replaced, but a few of the older ones need the complete valve changing.

tired_dad

Yep, it was the 3 way valve. 28 mm fittings. New one going in as we speak

DVardysShadow

For this type of system you will need the following to work [as an approximate guide]

• Programmer to provide supply when CH called for
• Roomstat to call for heating [set room stat to max]
• Divertor Valve to drive to CH position
• Pump to work

Note that if the valve does not drive to the correct position, the pump may not spin, even though it is OK - but dependant on the valve and the wiring plan adopted.