Nest thermostat wiring setup help!

[emmeth92]

No pic necessary. It’s quite easy, if you feel confident, and I don’t recommend this for just any boiler but yours is fine. Be careful as it’s mains voltage. You could turn power off to be safe.

There’s 2 screws on the front - if you look at the drop down panel there’s 2 magnets which align with the screws. Undo these slightly, lift off the outer cover. Then undo screws fully, being careful not to lose them.

Allow panel to drop down, follow cable on the left to a plastic housing, which I think is 1 screw, undo this, remove and you have access to the wiring.

Ah brilliant, I got in thanks to those instructions- thank you!

I took a few pictures there, is it just me or are the black and grey wires going nowhere? Might be hard to discern from the pictures but have a look

 

[emmeth92]

Ah brilliant, I got in thanks to those instructions- thank you!

I took a few pictures there, is it just me or are the black and grey wires going nowhere? Might be hard to discern from the pictures but have a look

 

[CBW]

Hard to tell exactly, but they appear to be wired via the clock? Have you looked on the left hand side?

 

[emmeth92]

Hard to tell exactly, but they appear to be wired via the clock? Have you looked on the left hand side?

Yeah I was thinking they were connected to the clock too.

Nothing on the left, but oh sorry I should add in case its not clear - the wires come up from the Nest from the *background* of this photo

 

[CBW]

Just looked again, and the black from the clock is looped. The main boiler power cable should be on the left.

 

[RandomGrinch]

Just looked again, and the black from the clock is looped. The main boiler power cable should be on the left.

Looks like it to me too - a bit of a bodge.
Maybe the correct terminal blocks were inaccessible due to the cabinet?

As a test (with power isolated), decouple one of the black wires from the clock (safely isolating it in another terminal block), and see if the central heating remains off.

Edit, I believe these terminals aren't linked in to the clock, but are on an extension cable, that dips under the pressure guage and into/around the PCB enclosure - probably connected to the correct terminals on the left hand side of the boiler?

 

[emmeth92]

Lovely - I'll give that a go over the weekend and see how it fares. Thanking you both