Wiring for Boiler

[alanthomaswatson]

Couple of quick questions please.

We're having a new boiler installed and the plumber has asked for a shuttered, unswitched socket outlet fused at 3A. I've checked the manufacturer's installation requirements and this is right.

Having taken the old electric shower out, we now have a spare way on the fuse board which I'd like to use to keep the boiler separate. Appreciate that this is Part P territory and the intention is that I will run the cable and fix the socket but a sparky will connect to the board.

1. I understand that buried cable doesn't need to be protected according to Part P. Is this correct? I'm providing trunking wherever I can but there will be some areas passing through walls, joists etc. where this is possible but more difficult.

2. As the socket is fused at 3A does this need to be run in 2.5mm or 4mm as a normal socket circuit or will 1.5mm suffice? Nothing else will be on this fuse.

Thanks again

 

[PrenticeBoyofDerry]

1) all cable has to be protected by a protective device ie fuse or MCB.
if you are referring RCD protection, special method of installation and materials allow RCD protection to be avoided but I advise you install an RCD.

2) Do you mean a fused connection unit rather than a socket?
The cable size really depends on the size of the protective device in the CU that is protecting that cable. You could use 2.5, 1.5 or 1.0mm if the protective device was suitable for the cable.

 

[alanthomaswatson]

Thanks for the quick reply.

1. Apologies if I was a little ambiguous - I meant protected as in put within channeling/trunking.

2. Nope, definitely a socket. It's on Vaillant requirements

Thanks

 

[mfarrow]

I've just downloaded an installation manual from Vaillant. It does indeed say to use a socket, however...

"Alternatively, a 3 Amp. fused double pole switch with a 3 mm contact separation on both poles may be used"

I'm not sure whether the 3mm is complied with on all these as part of the BS standard, but I would think a socket is the easiest choice.

An electrician will probably install an RCBO on the circuit unless an RCD is present on the board anyway (any big switch with a test button and 30mA written on it?).

1.5mm cable should suffice. 1.0mm if not going through any insulation.

 

[Taylortwocities]

If a new circuit is being installed for this purpose, I would use 2.5mm² cable with a B16 or B20.

This means that (if you install a socket) at the boiler end it will support the full 13A that the socket is capable of.

Who knows, some muppet might plug an electric fire in there (when the boiler fails) and pop goes your weedy 1.0mm² cable!