Honeywell cm907 change to hive heating

[Poida]

hi, I'm just wanting to double check that the wiring for this is as straight forward as I think it is.

I have a Logic ES35 combi boiler with the Honeywell CM907 that only seems to have a Live going to A and a Neutral going to B, there is nothing going to C. There is a grey wire not attached to anything, and an earth wire in the void space that also seems to not be attached.

Am I right in thinking I just use the Live and Neutral wires on the Hive?

 

[stem]

No you are not right.

Your existing thermostat is battery operated and doesn't actually have a L & N supply. The two terminals (A & B) are simply a switch, in that A and B are electrically connected together when the thermostat switches on, as the symbol above them shows.

I can see why you are confused, but if you look carefully at the diagram and you will notice that the N is connected to a rectangle in the diagram which represents the Neutral side of the heating load and not connected directly to terminal B. Terminal B actually provides the live to the heating load.

You will need the single channel version of the Hive.

The switching wires which are currently in A and B at the existing thermostat will go to Hive 1 (common) and 3 (Heating on)

Because the Hive is mains powered it will also require a new 230V supply connecting to N & L. This should come from the same 3A fused supply that supplies the boiler.

 

[Poida]

Thank you stem, yes I was confused as the colours for L and N weren't right for a new build property. What you said all makes sense now. So the brown wire goes to Hive 1 (common) and the black wire to 3 (Heating on)?

So because the current thermostat is near the front door and the boiler is at the back of the house I may need to put it closer to the boiler so that it's on the same fuse?

 

[stem]

Thank you stem, yes I was confused as the colours for L and N weren't right for a new build property. What you said all makes sense now. So the brown wire goes to Hive 1 (common) and the black wire to 3 (Heating on)?

Yes.