Central heating not coming on

[Norris1978]

Hi, looking for advice with a keston c36 combi boiler. The theemostat calls for the heating but the boiler doesnt respond. If i run the hot water for a bit then the heating kicks in. Ive read this might be the divertor valve or a capacitor.

Can anyone confirm this is the right line of attack?

(thermostat pt plus, appears to be working correctly)



Read more: https://www.diynot.com/diy/threads/keston-c-36-central-heating-issue.498729/#ixzz58iXr7DdK

 

[CWHEATING]

Definitely sounds like diverter valve to me. Just out of intrest if you run your hot water to run a bath or have a shower does your boiler cut out in overheat?

 

[Norris1978]

No it doesn't cut out (yet). I find that if i turn the boiler off and on the heating will kick in

 

[Daveydub]

I would check the microswitch on the diverter but more likely to be a air pressure switch related problem. Not really enough info to tell. Have you got ivy in your flue terminal?

 

[CWHEATING]

So if you run your hot water for long periods your heating comes on? If so I heard a while back that some combi boilers do this as a way of disbursing heat out off the boiler to avoid overheating and cutting out. Kind of like a bypass valve.

 

[Norris1978]

The centel heating will only come on if i run the hot water or i turn the whole system off and on again. Kinda like a reset.

 

[picasso]

Have you tried new batteries in the stat ?

 

[CWHEATING]

Sorry hard to pin point an exact problem with the situations given.

 

[Norris1978]

Yes tried new batteries. Makes no difference

 

[picasso]

Does the receiver light up when you use the stat ? drayton digistats are well known for the capacitor to fail in the receiver.

 

[Norris1978]

Yep green light comes on. So is calling for heating but temp doesnt go up till i turn hot water on or turn boiler on and off

 

[picasso]

Green light might be on but can you hear the relay click when you turn the stat up ?

 

[Daveydub]

Drawing a bit of hot water, the boiler fires. Turn off hot water ch continues to run.
Problem with flue/APS, boiler turns on for ch, fan runs at 70%, not enough flow to trip APS.
Draw HW, fan runs at 100%, Aps trips & boiler fires.
No guarantee just the first area that I would be checking.

 

[CWHEATING]

Yep green light comes on. So is calling for heating but temp doesnt go up till i turn hot water on or turn boiler on and off

I wonder if it’s actually a boiler problem. Maybe PCB?

 

[Daveydub]

Maybe PCB?

Could be or perhaps ivy in flue or hole in aps tube.