Nest Thermostat E replacing Drayton Mistat

[Luetchy]

Good afternoon!

I did have a browse though other threads to see if I could find an answer, but unfortunately not.

I have followed the instructions as far as I could, but I cannot get the boiler to power back on. I've checked fuse/trip and nothing has gone. When I first wired it, I put the wrong wire in the Nest and the boiler did turn on but I had no heating (hot water still works, so I know the boiler can fire up). When I checked and replaced the wires, the boiler will not power on now.

 

[UpgradeME]

It looks like you have connected the wrong wires. The Drayton wiring diagram shows Grey (common) & Black (call) are connected together when the thermostat calls for heat - You have connected the Brown in (C)ommon instead of Grey.

 

[Stuckinarut]

It looks like you have connected the wrong wires. The Drayton wiring diagram shows Grey (common) & Black (call) are connected together when the thermostat calls for heat - You have connected the Brown in (C)ommon instead of Grey.

Doesn’t explain why the boiler won’t come on, unless the live isn’t daisy chained through the Drayton receiver/fcu.

 

[Mister Banks]

Doesn’t explain why the boiler won’t come on, unless the live isn’t daisy chained through the Drayton receiver/fcu.

Unless switching the live has blown the PCB in the boiler.

 

[ianmcd]

what boiler do you have ?

 

[dilalio]

Putting the brown wire into common on the nest could potentially have relayed 240V through to the boiler connection and if this is on low voltage or volt free terminals on the boiler - could fry the PCB.

As per @Mister Banks above.

 

[Stuckinarut]

Unless switching the live has blown the PCB in the boiler.

Of course, doh!!!

 

[dilalio]

@Luetchy - I guess you didn't want to hear the above!
If it makes you feel better... You ain't the first and won't be the last if you've nuked the PCB! Yes, it is an expensive lesson but a lesson nonetheless.