Heating Stops!

[cuban8]

The problem is intermittent and may only happen one day in four or maybe three times a day. Essentially, what happens is the system will not run although the room 'stat is calling for heat and the controller is on.
The problem seems to occur when the room 'stat reaches is selected temp, cuts the system off and then will not restart when the room cools off. The circulating pump is off and the boiler is off. Often we return to a cold house after leaving the 'stat on say 24C. The only way to get the system back on is to switch the controller mains supply off for a while and switch on again. The system then fires up and continues without fail. The electronic controller was replaced today so no joy there. A control board in the boiler (Potterton) was changed three months ago to cure a separate poor starting problem there. A replacement 3 port valve was also fitted 6 months ago as it had seized.
This snag has come about over the last couple of weeks, the system has otherwise been ok since the other work.
Any ideas?

Thanks
C8

 

[ChrisR]

What room stat is it - digital or a clicky dial one?

Next time, try turning HW on, and see if that gets the boiler on. (HW would have to be cool enough of course)

Trouble is, almost anything can be intermittent.

 

[cuban8]

What room stat is it - digital or a clicky dial one?

Next time, try turning HW on, and see if that gets the boiler on. (HW would have to be cool enough of course)

Trouble is, almost anything can be intermittent.

Hi.

room 'stat is mechanical click type.

Question... does the 3 port valve send a "signal" to the rest of the system that allows the boiler/pump to run?

Cheers.
C8

Cheers

C8

 

[kevplumb]

Question... does the 3 port valve send a "signal" to the rest of the system that allows the boiler/pump to run?

yes orange wire is switched live (if the old grey matter still works)

 

[ChrisR]

for CH it does , yes.

 

[cuban8]

for CH it does , yes.

Think we may be on to something here. Will do some checks tomorrow morning and will let you know.

Thanks for your help, Gents.

C8