Nest Thermostat e uk


Novice Member

Looking for some help identifying which wire on my old thermostat is common and which one is not open. The instructions supplied with the nest are as clear as mud. Attached the wiring diagram located inside the housing and picture of the wiring itself.
Black is in terminal 1, brown is terminal 2 and blue is terminal 4
Thank you in advance


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Seb Briggs

Well-known Member
NO is normally open

it means that when a signal happens it closes the circuit to start the boiler , and when no heat is required it opens up again and the boiler goes off

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