Replacement heat link to boiler - wiring query!

[Litchy1986]

Hi all!
I’m switching out an old centre heat link with a nest one to my combi boiler.
My first question is:
Does the wiring diagram attached, and the wiring in the photo, align? It feels strange to have the two wires in the single point within the power side of the heat link, but I’m not an electrician!
Many thanks in advance!

 

[CBW]

Yes, that’s basically a common. It’ll need one in the heat link too. Two if you’re doing the hot water side.

 

[Litchy1986]

Perfect thankyou.
Following on from this, when wiring in the nest heatlink, I’m assuming the following:
-(N) neutral from power, neutral to boiler
-(L) live from power, live to boiler
-(3) black from boiler (as per original centre heatmap location 2).
The loop from the centre layout appears to move from (L) to (A), changing to (L) to (B), as per the nest wiring diagram.
Does this sound about right?
Many thanks!

 

[CBW]

Not sure if you’ve understood it properly, as I can’t follow what you’ve said entirely. You have the L and N correct, then the link would go from L to 2 in heatlink and the black would go to 3

 

[Litchy1986]

Yeah your summary makes sense. Thanks again for the input, very much appreciated!
Alec

 

[ericmark]

It is normal to feed boiler, then feed the thermostat from the boiler, so if a fuse blows in the boiler then all power is removed. It will work thermostat then boiler, but that means you have two supplies to boiler, and should a fuse rupture then the boiler could still be live.

My boiler is very simple, supply on it runs, supply off it stops, it does not have a permanent line, so with my boiler supply to thermostat then to boiler is OK. So it does depend on boiler type.