Central heating problem (UK)

[Vaughn Ritchie]

My dilemma: I have Gas central heating ('S-Plan' with two port valves. Hot cylinder also has an immersion heater). No activity at the relevant zone valve when 'calling' for hot water.
Powering the Immersion heater does activate the hot water zone valve. I have a non-vented cylinder, fitted during a bathroom refurbish.
Any help appreciated. Vaughn.

 

[Leesparkykent]

My dilemma: I have Gas central heating ('S-Plan' with two port valves. Hot cylinder also has an immersion heater). No activity at the relevant zone valve when 'calling' for hot water.
Powering the Immersion heater does activate the hot water zone valve. I have a non-vented cylinder, fitted during a bathroom refurbish.
Any help appreciated. Vaughn.

The immersion has nothing to do with the two port valve. You need to work through the sequence of switching....programmer when calling for heat sends power to the cylinder thermostat, the cylinder thermostat then sends power to the brown of the two port valve if it’s calling for heat, the two port valve then opens and when opening it closes the micro switch between grey and orange of the two port, the orange then switches the boiler. As it’s an unvented cylinder you will also have a high limit thermostat wired in series which will have a reset on it. If the high limit thermostat needs resetting then you need to find out why.....If you have an approved voltage indicator, knowledge of the order of switching then it should be easy to find why it’s not firing the boiler.

 

[Wilko]

Hi - has the CH been working properly till recently? Any other changes or work done? It is usual for the standby immersion heater to be independent of the boiler and valves. It’s usually a 3kW heating element with its own thermostat, but I might have misunderstood .

 

[EricMark]

I had to read and re-read, then it twigged, if the immersion heater heats the cylinder then the thermostat for the central heating boiler will open so the motorised valve will close.

But there is no electrical connecting between the two systems.

I would guess the micro switch has failed in the motorised valve, I would also guess if central heating running then DHW also gets hot, it just will not start the boiler?

Many motorised valves can have head replaced without replacing the whole valve.

 

[ferg]

It is possible that the immersion has been wired in to the stat terminals on the cylinder.
Switching on immersion would activate valve if this was the case.

 

[steve2018]

Just to clarify:
Is there no power to the powerhead? Problem not in the zone valve if so.

Hard to say, is the valve or the assembly sticking?

Get all the information, including valve name, model, serial numbers, and pipe size. On multiple installations, you must state which valve failed and tag it.
Ask around for a service guy.