Thermostat Wiring Puzzle

[briandayson]

Help! I have purchased a new Thermostat/Controller (Siemens REV11) but it only has 2 connections and the old thermostat has 4 (see pictures at link below).

Which of the four wires should I connect to the new controller?


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[seco services]

live in L common
switch live in L1

the other two are neutral and earth not needed.

 

[briandayson]

Thanks but I'm still confused. I've got Red, Blue, Yellow and unshielded - which is which?

 

[seco services]

you have to check with a multi meter.
as people use different colour wires and don't label them properly.

so check for a live on one when the programmer heating on.
switch live
neutral, earth.

earth, neutral not needed on new one.

 

[briandayson]

That's brilliant. Thank you for your help - I will try and find someone with a meter I can borrow.

I am in serious danger of becoming competent at this stuff!

 

[Axel]

Competent or not, be mindful of what you do with the unused Earth and Neutral wires. If they join it could trip an RCD in the consumer unit, and in any case, all unused wires should be either terminated safely (ie, connected to dummy terminals) or disconnected at the other end. Good practice to leave earth wire connected as it protects the cable.