Replace Honeywell Wireless with Nest Heatlink (cabling)

[Zarch]

Hi all,

I've got a CMT921 Honeywell kit with the CM900/R6660D wireless relay box sat next to our old Ferroli Modena combi-boiler in the coal shed. (Wiring picture shown below)

I'm hoping to purchase and install Nest in the coming week.

I think it makes sense to install the Heatlink in exactly the same place as the current unit and i'm hoping to use the same cabling.

Then the actual Nest controller will then sit in the house talking wirelessly to the heatlink. Its only about 8m through a wall.

So i'm happy that with N to N and L to L. Correct?

But what about A and B on the Honeywell in relation to Nest 1, 2 and 3?

Any help would be appreciated.

Thank you.

My Wiring


Honeywell Doc


Nest Doc

 

[D_Hailsham]

A = 2
B = 3

 

[twixx]

Does this help?

//www.diynot.com/diy/threads/nest-install-2-wire-replacing-existing-stat.398926/

 

[Zarch]

A = 2
B = 3

Thank you very much, as easy as that.

 

[Zarch]

Hello all, Thanks for the info provided before........ I installed the Nest heatlink fine and positioned the thermostat in the living room using the supplied USB power supply.

Wife has now decided she doesn't like where the thermostat is placed and has asked for it be moved.

Unfortunately, there is no mains power close by to the new location, so i'm going to run some cable from the heatlink and use the 12v power option.

My question is about the spec of cable required for the 12v feed? Do I just need some 2 core? What A rating? The thinnest cable I can away the better as it will be seen in places. Length will be about 8 metres.

Also, if replace the Nest in the future (Honeywell Evohome perhaps?), is it worth laying some other type of cable whilst i'm doing this?

Thank again.

 

[jackthom]

Almost any 2 core cable will be fine. The Nest thermostat will take somewhere around 1 Amp from the Heatlink supply.