Replace Drayton LP711 with Nest

[ClaphamLondon90]

Have a baxi duotec 28. Drayton LP711 is wired in and I want to swap in the Nest.

N+L and 1(COM)+3(ON) is wired on the LP711. Along with a link to the Honeywell controller.

So on the Nest wire N+L the same

Disconnect the Honeywell controller by removing the link between the blue+grey cable. Disconnect the brown cable from 3(ON) on the LP711.

Then wire the black cable 1(COM) from the LP711 to 2(COM) on the Nest. And the grey cable which was in the link to 3(CHF) on the Nest?

 

[CBW]

Which Honeywell controller? Best posting photos of wiring

 

[ClaphamLondon90]

Honeywell t3630, picture of wiring attached

 

[CBW]

Ok, so you could position the Nest thermostat in place of the Honeywell using the 2 wires there already, and where these are at the LP711, connect to T1 and T2. Then you put the heatlink where the LP711 is and wire that accordingly, so L - L, N - N, Com and NO

 

[ClaphamLondon90]

Ok, so you could position the Nest thermostat in place of the Honeywell using the 2 wires there already, and where these are at the LP711, connect to T1 and T2. Then you put the heatlink where the LP711 is and wire that accordingly, so L - L, N - N, Com and NO

Tried that albeit, without the Nest thermostat being linked using the existing Honeywell wirings from T1+2 on both ends. I have the Heatlink wired L-L, N-N, COM-COM, ON-ON. Turning thermostat on the boiler pump starts going, radiator symbol flashes, but it doesn't fire to heat. Fires to heat just fine for hot water.

 

[ClaphamLondon90]

Update: It is working, I was just being impatient waiting for it to fireup. Left it for a good 15 mins and came back.