Diverter valve issue

[SecretPrawn]

Hi,

We recently have had our old thermostat replaced with a Google Nest. However, we are having an issue with central heating.

It now will only come on when the hot water is also being heated.

I've had a look at the diverter valve, which has the markings "H M W" on. The indicator defaults to W.

When the central heating is turned on, it remains in "W".

When the hot water is turned on, it moves to "M".

When both are on, it moves to "M".

Under no combination does it move to "H".

If I press the switch on the side of the valve, it moves to "M" and then moves back to "W" when I release the switch.

I'd expect that for hot water only it would stay in "W", and that for central heating only it would move to "W".

I'm still playing around with it, but I think this is also resulting in the central heating not turning on when the hot water tank is up to temperature.


Before I start getting the electrician back, or calling in a plumber, is anyone able to advise if this is likely to be a wiring issue (and is there an easy \ safe way to check this?), or is this likely to be a valve fault?

Thanks for any thoughts or help.

Tom

 

[terryplumb]

When selecting heating only at programmer ,the MPV should move to H not W as you stated above.
When was the stat replaced ,and did system ever work properly after it was replaced ??

 

[ianmcd]

Post a pic of the wiring in your nest, sounds like it has been done wrong

 

[SecretPrawn]

Thanks for the replies:

When was the stat replaced ,and did system ever work properly after it was replaced ??

No - which makes me think something isn't quite right rather than the valve suddenly dying!

Post a pic of the wiring in your nest, sounds like it has been done wrong

Please see image attached, thanks for your thoughts!

Tom

 

[ianmcd]

Thanks for the replies:



No - which makes me think something isn't quite right rather than the valve suddenly dying!



Please see image attached, thanks for your thoughts!

Tom

You dont have a wire in terminal 4 HW OFF , that is your problem

 

[SecretPrawn]

Thank you very much - I'll ask the electrician to have a look at that.

Tom