Installing Nest in New Build

20 Feb 2018
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United Kingdom

I have just moved in to a new build home and am thinking about replacing the thermostats with Nest 3rd Gen. The property is Gas and has instant hot water. The house is zoned, upstairs and downstairs with a thermostat in each zone.

Boiler = Ideal Logic Combi c30
Programmer = Danfoss FP975
Wiring Centre = Danfoss WC4B
2 x Thermostats = Danfoss RET1000M

Images attached of current set up and wiring inside the wiring centre.

2 - Room Stat - Call - 2 x Brown
3 - Room Stat - COM - 1 x Brown, 1 x Grey
9 - Programmer - HTG ON - 3 x Grey
10 - Programmer - HW ON - 2 x Orange, 1 x Brown
13 - Pump - L - 2 x Brown
14 - CYL STAT - Call - 1 x Grey, 1 x Brown

Also 1 x Brown, 3 x Blue , 2 x Black and 4 x earths on show.

Could someone help point me in the right direction as to how to split the current wiring in to two separate Nest Heatlinks?

I would like to try and do it myself as opposed to have an electrician do it but will call on an electrician if it comes to it.

Any help would be appreciated.

Thanks in advance,


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Last edited:
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Sorry, but I don't think this is one for DIY. It's not straightforward and there is a fair bit of scope for error.

You say that you have instant hot water from a combi, but this must be only half of the story, as there is also a programmer with a hot water channel, and a cylinder thermostat.

The two RET1000M room thermostats only provide temperature control, and not time control, which is provided at the programmer. However, the Nest combines the two functions into one, so the wiring will need consolidating to bring the presently separate time, and temperature control together for each zone, and at the same time if the programmer presently provides time control for both zones, this would need separating.

Personally, due to the extent of the modifications, I would be inclined to disconnect the whole thing and wire it up again from scratch. The stored hot water would be included with one of the Heatlinks, and the second would solely be for the second zone. As per the wiring diagram you have posted, terminal 3 is for the heating 'on', and terminal 6 is for the hot water 'on'

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