Help with swapping Hive to Nest Thermostat E - which wire goes where?!

[cjm_drw]

Hi everyone

I am trying to swap out a Hive system to a Nest Thermostat E in the UK. I am confused by the wiring to the Heat Link. The Hive unit is wired like this: Blue to Neutral, Brown to Live, Green/Yellow to an earth terminal, a Grey wire goes to 3, a Black wire goes to 1, and there is a jumper from L to 1. I'd be grateful if someone could help me, which wire goes where on the Heat Link? Many thanks in advance

[AlexD]

Hi @cjm_drw , thanks for reaching out here. I would be happy to assist.

For starters, have a look at this Google Nest E installation video. You can see the whole process as well as the wiring.

In short what you need is a live wire going to terminal C, the common. You will not use earth or neutral. In terminal NO you'll need to put the call for heat wire, the wire that goes to your boiler. I can't say for sure what wire this is for your current thermostat as they are only labelled with numbers but it's most likely the one for terminal 3. Since there is a jumper from L to 1, that terminal would be permanently live so it's unlikely to be that one. If you are unsure it would be best to get an installer to check the wires and determine what each are or check with the thermostat manufacturer as they may have a manual or diagram stating what wire goes into each number.

The last terminal FP will usually be empty and the OT1 and OT2 terminals are used for OpenTherm systems. 

[cjm_drw]

Thanks for your reply. Unfortunately the set up you suggested blew the 3 amp fuse. But it was worth a try to save some pennies . I’ve contacted an installer 

[AlexD]

I am sorry to hear that. As i mentioned since they are numbered there is no way of knowing for sure. If possible check with the manufacturer or if you have a manual what each terminal is on your current unit or get in touch with an installer to check and determine what each wire is. 

[Vladut]

Hi there, just checking in with you. Did you manage to check the last message?