Nest install with Potterton 2002 and 4 wire Honeywell thermostat

[Chris Dainton]

Possibly been answered before, but going to install a nest learning system and I am wondering about the thermostat. I want to remove and use the existing wires for the nest - my question is, I have 3 wires and an Earth at the thermostat. Do I remove all four wires from the thermostat at the switching box ? And then use two wires to plug into T1 and T2 to power the new nest thermostat. I know I have to bridge the wires, but does removing the blue wire completely and not replacing it have any consequences ?

 

[Chris Dainton]

Here are the photos of all the wiring

 

[ericmark]

Not quite, you use 3 wires, T1, T2, and earth. With mine I found not enough room in heat link, so mounted a box below it. I was very careful that there was no connection to mains supply, but it says connect earth so I did.