Nest Thermostat Installation

[chalky74]

Hi,

Just recently purchased our Nest thermostat, haven't tried wiring it in yet but have been looking at the manual and just trying to get it right before I start.

Currently using the Honeywell CM921 thermostat and relay box with a Baxi Duo Tec combi boiler.

According to the Nest manual I need connect a Live and a Neutral which I get and can identify easily in the CM921. But also it says I need to connect a "call for heat" (2) and a "common" (3). The but I don't understand is there are two wires in the CM921 that are connected to a terminal block labelled A and B.

My question is, is A in the CM921 "call for heat" or is it the wire connected to B. Presumably if A or the B wire is call for heat the other would be common?

Any help would be appreciated.

Thanks

 

[nortonj]

Yes a is call and b is common.
I think it will still work if wires reversed

 

[D_Hailsham]

Yes a is call and b is common.
I think it will still work if wires reversed

Er no, it's the other way round. But, as you rightly say it doesn't matter if the wires are reversed.

 

[nortonj]

Thanks for pointing that out.