Nest 3rd Generation Upgrade

[haz786]

Hi all,

I've purchased a Nest 3rd Gen & looking at replacing the current controller. The system currently has a combi boiler & electric water heater.

Image of current cabling is attached - cables in N, L, 3 & 4.

If you could direct me where this corresponds on the HeatLink, that would be greatly appreciated.

Also - how does the electric water heater factor into this? It is located on the 1st floor and powered manually with a switch when required (so don't think it's directly connected to the controller but would like it linking into Nest if possible).

Thank you

 

[muggles]

What make/ model is your existing controller?

 

[haz786]

Hi there,

Existing controller is a Danfoss FP7898

 

[stem]

I seem to think that product refers to the 715 as below. is that correct? It will say on the drop down door bottom right corner.

If so, there is something a bit unusual. Are you sure you actually have a combi boiler? A combi boiler heats the hot water instantly whenever a hot water tap is opened, and the hot water goes directly from the boiler to the tap without the need for a hot water cylinder (tank). However, if your programmer is the same as the one above with a 'tap' symbol and the wire connected to terminal 3

That indicates that the boiler is connected to a hot water cylinder. I suspect that this is the case and that the cylinder has an immersion heater fitted as a back up. Is that right?

If the boiler is connected to a hot water cylinder and the programmer is a 715, installation of a Nest thermostat has been covered on here before. You can find an example here. You don't have a wire in terminal 1, so your system is slightly different. Just ignore that bit.

 

[ianmcd]

Danfoss FP7898

That is a programmer so unlikely that you have a combi boiler post pics of your boiler and what you are calling an electric water heater