Honeywell T40 to moes bht-002 installation help

[Deleted member 267285]

but the wiring centre might be in a cupboard or under the floor

Ah, might be an issue then

 

[Antoniokra82]

Another chapter to the saga.
I started to look everywhere in the house and opened every cupboard when I found this junction box next to the water heater. And connected to nothing I have found the blue cable. I have buzz it and it is the one going to the thermostat.
Unfortunately I have the same issue, I don’t have any neutral inside the box (tried every cable).
I have the power supply of the water heater nearby but it is not the best practice to share the neutral even if it is on the same circuit of the boiler. Any thoughts?

 

[stem]

When you say next to the 'water heater' do you mean the hot water cylinder? If that's the case then usually the motorised valves for controlling the hot water will be close by, and will have a neutral supplied by the heating circuit. If so, a cable could be run from that to the unconnected neutral in the terminal box.

 

[Antoniokra82]

I couldn’t find any motorised valve but I have the supply for the water heater on a fuse spur.
Can I just not “steal” the neutral from it?
This is on the same supply of the programmer and the boiler

 

[stem]

It's not advisable and a professional wouldn't do it. The entire heating system should really be fed from the same fused spur, so that when it's switched off the entire heating system is isolated from the mains supply completely (both L & N). If you want a more definitive answer you could always ask this question in the electrics forum. There is a term for what you propose and you are close with "steal"; The term is actually 'borrowed neutral'.