Nest installation wiring help

[Gringoking88]

Hi all,

I am trying to wire a nest 3rd generation thermostat into what I believe to be a s plan heating system and am after a bit of help please.

Upon removing the cover for the old programmer, there appear to be two wires to each port please excuse my ignorance, but why would this be as it does not seem to follow the wiring diagram???

I have attached pictures for reference.

Many thanks in advance,

Martin.

View attachment 35129

View attachment 35130

View attachment 35131

View attachment 35132

 

[Leesparkykent]

3 is HW on and 4 is CH on. Do you have an existing room thermostat that the nest thermostat is replacing?

 

[Gringoking88]

3 is HW on and 4 is CH on. Do you have an existing room thermostat that the nest thermostat is replacing?

Hi Lee,

Thanks for that, I understand the hw on / ch on but don't understand why the two neutrals, 2 earth's, 2 lines???

Yes I do and wanted to power it using the existing cable being supplied from the 12v on the heatlink.

Thanks,

Martin

 

[Wilko]

Thanks for that, I understand the hw on / ch on but don't understand why the two neutrals, 2 earth's, 2 lines???

Is it as simple as the supply is taken from a ring circuit? This typically is where a 32A circuit breaker is used to protect a looped 2.5mm2 twin and earth cable that has 13A outlets on it. Each outlet then has one cable in, and one out to form the loop back to the mcb.

 

[Gringoking88]

Is it as simple as the supply is taken from a ring circuit? This typically is where a 32A circuit breaker is used to protect a looped 2.5mm2 twin and earth cable that has 13A outlets on it. Each outlet then has one cable in, and one out to form the loop back to the mcb.

Wilko,

I feel like a bloody Muppet, your absolutely right!!!

I remember now when isolating at the board it was not supplied from the hot water circuit but only isolated when the sockets were turned off. That's it, spured off the ring main.

Brilliant,

Many thanks.

 

[Octopus]

Hope it's not directly connected to the ring without a fcu

 

[Leesparkykent]

Yeah perm live and neutral...probably supply from load side of switched fused spur and feed up to wiring centre. You will want to get rid of the programmer then or leave it on constant which isn't ideal and install the heat link next to or in place of the wiring centre.