CH but no Hot Water

[topgazza]

I’ve called my local plumber and I am interested in peoples thoughts whilst I wait.

I have an unvented system and a trusty Potterton Netaheat profile 50e boiler. Intermittently hot water would fail to work. Then it would be fine. If I hit the BG controller it would often work. Weird but I replaced the programmer with the Drayton 722 direct equivalent. I’m an electrician so happy to do that much. All seemed well until this morning. No HW. Checked voltage through cylinder thermostat and 240v in and out so I assume that’s ok and demanding HW.
As I say waiting on my excellent local guy but any thoughts ? Boiler controller ?

 

[ianmcd]

More likely to be a faulty zone valve or 3 port valve , which system do yoiu have Y plan or s plan ?

 

[topgazza]

S I think Ian. Just two 2 port valves from the look of it. Both mechanically work with resistance and the diverted for the HW I think, Drayton Zone Valve Actuator, fires the boiler if manually push the lever. But it returns to home and boiler goes off

 

[oilhead]

If you have a live feed from your cylinder stat to the live on your 2 port valve and it's not opening, then it's probably a failed synchron motor in the valve. About £20 from Screwfix, and it comes with the little spades fitted.

 

[topgazza]

Good tip worth a go whilst I’m waiting. The valves not that old but things fail as we all know.
Thanks

 

[topgazza]

The microswitch in the valve is sticking and also looks like it is intermittent in being actuated. So I’ve ordered a new valve from Screwfix.

I’ll feed back the results