Heating Wiring Problem - cylinder thermostat not working

[Aaron b]

If this was something I was asked to look at I would check the voltage on the control to the boiler (call for heating), I would prove the function of the boiler using a link between 3 and 4 I would prove be wanting to prove it was off when the link wasn't in place and that it fired up with the link. If not I'd call valiant and speak to there technical dept.

To prove the nest stat I would want to see the valves move. I think you can press the button on the controller to get it to call for heat. The arm moves on the side and I think it goes loose when energised.

To check the connections through the valves I would probe between earth and the orange from the valve in the energised and the de-energised positions. I'd only expect voltage on the orange core when the valve is open.

 

[westward10]

Thread closed. @dfreitag this has been going on for a week with multiple step by step posts which cannot go on. Find a competent heating engineer.

 

[dfreitag]

OK, so after finally finding a competent heating engineer, I though it could be helpful to share the solution!

Thanks @westward10 for temporarily reopening the thread!

Turns out the culprit was the Heating valve, which was faulty and sending a permanent live to the boiler, independently in which position it was on..

By replacing that valve, the issue was solved. (annoyingly a previous contractor had changed the HW valve - so the wrong one)

(Seems quite plausible in hindsight to be honest, but I guess it almost always is afterwards..)

The engineer also re-did the wiring from scratch, and with a rather clean result - please see below photos of all items.


Hope it is of help for someone out there! I'm definitely relieved to have a working HW and heating systems, before winter and those massive bills hit...

All the best
tsomek

 

[littlespark]

Glad its all sorted....

How did this thread have over 2000 views in the space of a month?

 

[Stu435]

Nest wiring: The green/yellow appears to have been used for 'hot water on', since it's connected to 10 at the wiring box. Wires can be used for purposes other than that indicated by their colour if a short identifying sleeve is fitted over the wire at each end, BUT this does not apply to a green/yellow wire. This can only be used for earth and for no other purpose.
The cable used appears to be only 4 core, so should be replaced by 5 core, with the green/yellow used for the earth connection to the nest, and the grey (with brown sleeves at each end) used for 'hot water on'.

Hi. I know this is a couple of years old but I think just as valid now as then. Does this rule apply for extra-low voltage control wires?