Save £100 wiring a Nest (3rd Gen) to my boiler

alistone

Got the cover off the current thermostat and it looks like this....

drive.google.com/open?id=1WDdJoznmXUIjZ3zjD-Z6M8tg2Dml9h_F

benjus

antilles wrote: »

Looks like it already has thermostat connected to me via the black and grey wires (they appear to have brown sheathing pushed over them unless I'm mistaken) - are those the thermostat connectors? They usually have a link between them which looks as though it's already been removed. So could it already have a thermostat connected? Looks like 5 core cable to me.

I'd bet those black and grey wires are connecting to a thermostat at the other end.

Sorry, you're right... I originally thought that was an oversized loop of wire shorting out the room stat terminals, but I should have looked more carefully.

Anyway, the instructions are the same - remove the wires connected to the 2 right most terminals and connect the 2 right most terminals to terminals 2 & 3 on the Nest heatlink.

alistone

Ah ok thanks guys! So I disconnect the old thermo and attach the nest heatlink to terminals 2 and 3. Do I need to connect any other wires, for power to the nest heatlink for example? Assuming I can then simply remove the old thermostat downstairs as it won't be connected to anything?

Debbie_Savard

IIRC the Heatlink needs 240V mains power

benjus

Yes, you'll need power to the heat link (terminals L and N), which you can take from the power supply to the boiler (the middle terminals on the boiler). Once you have disconnected the old thermostat from the boiler you should be fine to get rid of it. I'd always recommend using a volt meter or mains tester screwdriver to make 100% sure that none of the wires are still live.

The other thing you need to consider is how to power the Nest thermostat. You can either use the T1 & T2 supply from the heat link (if you want to put the Nest thermostat in the same place as the old thermostat, you can re-use the existing wires for this), or you can use the USB power supply that comes with the Nest.

alistone

Thanks that's great! I'll try this tomorrow. I think we'll go with the USB as the current thermo is in a silly place above the radiator downstairs!

Will let you know how I get on