Replace

[Steve Wegerle]

Hi,

I'd like to replace my British Gas Thermostat with a Nest. I've taken the BG one off the wall and confused by the wiring, hoping somebody could help with how to wire it into the Nest for my central heating and hot water?

Thanks,

Steve

 

[Wayners]

Old thermostats are just live in and live out. No neutral wire.
Old thermostats are a switch on and off.
I think the nest needs live and neutral plus a switch wire.
Not my area and never fitted one

 

[RandomGrinch]

The Nest 3rd gen Heatlink, would replace the Drayton LP522.
Ideally, the BG WS4 could be linked out and the redundant stat removed - however, there is a bit of wiring behind there to interpret.

If you don't want to mess around too much with wiring, keep the WS4 in place and simply turn it up to maximum.

To replace the LP522 with the Nest Heatlink...
The two wires in N on the LP522, would go to N on the Heatlink.
The wire in L, would go to L.
The Grey wire in terminal 3 (HW NO), would go to Nest terminal 6,
The Brown wire in terminal 4 (CH NO), would go to Nest terminal 3.
You would need to add short link wires between L, and terminals 2 and 5 on the Nest.
The earth wires would go into the Nest earth terminal.

Just to note, the terminals in the heatlink can be a little tight, when trying to fit multiple wires in - it can sometimes be easier to make multiple connections into a Wago, or separate terminal block, and then take a single wire over to the Nest.

If you do want to remove the thermostat completely, let us know, and we can delve further into the wiring!

I hope that makes sense.

Edit: just realised I'd responded to your other post - you are changing a few thermostats at the moment!

 

[Steve Wegerle]

Haha @RandomGrinch yes I am! I've had 3 Nest E thermostats gathering dust since I had an extension done. I've got 3 in total I want to do; 1. is my main house thermostat that controls the central heating and hot water, 2. separate thermostat for wet underfloor heating in the kitchen and 3. another separate thermostat for my converted garage.

With your help, I was successfully able to do the garage. The post above is trying to tackle the main house thermostat but the connections on my heatlink do not correspond to your instructions (picture attached). Could I humbly ask for you to have another look at it?

Thanks,

Steve

 

[RandomGrinch]

Haha @RandomGrinch yes I am!

The post above is trying to tackle the main house thermostat but the connections on my heatlink do not correspond to your instructions

Your thermostat E doesn't have the hot water control that the 3rd gen Nest does.
If you want to change to the E, you will need to retain the LP522 for control of the hot water.

It may actually be worth leaving the wiring in place completely for the LP522 - you could set the heating to permanently on, and replace the BG WS4 with the E Heatlink, instead.

Although retaining the LP522 would be a bit of a shame, as you have the Nest ecosystem for everything else.