Honeywell thermostat

[Lee goodwin]

Hi there,
I very new to this site but I am looking for some help on how switch my honeywell thermostat over to a Google nest thermostat which I have put a picture of the wiring diagram, but I have hit a wall as took off the cover of honeywell I noticed that the wiring is not the some. As you see from pictures I got X2 red wires 1x black wire and x2 yellow and green which I know is Earth. The 2 red wires are going into No1 and No3 and black wire is in No
Now I know that No1 is the power with No3 being comms but what is black because as I turn the heating on red No3 and black No2 comes alive and heating come on. The heating is on a timer which is in the airing cupboard to were my hot water tank is. Anyone who can help I would be very grateful.

 

[CBW]

No2 comes alive

Like Frankenstein’s monster? Joking aside.

Hello Lee, I can’t see green/yellow wires in that photo, only what looks like an earth, which would be correct. Have you tested these terminals on the Honeywell for voltage? If no, then number 1 would be Common on Nest and number 3 would be normally open (NO) on Nest.

 

[Lee goodwin]

Hi there, the 2 earth wires haven't got a yellow and green cover on them, so that's both No1 and No3 reds wires, what about the black wire that's in No2 that's the wire that's got thinking or stumped???

 

[CBW]

The black wire is the neutral wire, required for none battery types to prevent temperature swings.

 

[ianmcd]

you will have to safely isolate the earth and neutral wires

 

[Lee goodwin]

Hi there, following my other pictures I put up, I manage to take picture of the inside off my honeywell cover. This is were I am confused, I know now from Chris W were/what the red wires but it's this black in No2 I can't not figure out. The 2 earth wires I got terminal block for them. I need help on this black wire. Any help will be very grateful..

 

[ericmark]

1 and 3 go to C and NO on Nest other two put in a connector block safe for latter use. In theory 1 is same as C and 3 same as NO but if swapped it would not matter.

 

[Lee goodwin]

So the black wire isn't important????

 

[CBW]

The black wire is the neutral wire, required for none battery types to prevent temperature swings.

help on this black wire. Any help will be very grateful..

See my reply? The black is a Neutral wire, does your Nest need one? - No it does not. Terminate safely in a
terminal block as per @ianmcd

you will have to safely isolate the earth and neutral wires

 

[Lee goodwin]

Hi all,
I would like to say thank you to all who helped with my honeywell thermostat wiring on changing it over to my new Google nest.