Help with extending garage CU cable

Adamstc222 · Apr 22, 2024

Hey everyone, working on a new build house and outside garage is wired up like this, however customer wants a Garage Consumer Unit instead of the plug but not sure what the best way to extend the cable would be as its too low to put a consumer unit where the plug is? any advice would be helpful

[ElectriciansForums.net] Help with extending garage CU cable

davesparks · Apr 22, 2024

By plug so you mean socket?

A suitable joint box is needed, I'd probably use a besa box for something small like that?

Why do they want to replace a socket with a consumer unit?

And why is that too low for a CU?

James · Apr 22, 2024

so, a cable comes from the house (swa)
is connected to a fused spur and then continues on to some sockets and a light?

where is the swa fed from?
what size is it 2.5 or 4mm by the looks of it.

A submain to a distribution board should not be fed from a spur off a socket ring.

I think (and I am making some guesses here) it is unlikely to be suitable to use the existing supply cable unless it is fed from its own breaker in the house DB.

Adamstc222 · Apr 22, 2024

davesparks said:
By plug so you mean socket?

A suitable joint box is needed, I'd probably use a besa box for something small like that?

Why do they want to replace a socket with a consumer unit?

And why is that too low for a CU?

Yeah a Socket, they are looking to upgrade their garage so want a consumer unit out there but the plugs are really low down and I feel it would be better to have the consumer unit higher then the height of the plug as it wouldn't look great that low down.

Adamstc222 · Apr 22, 2024

James said:
so, a cable comes from the house (swa)
is connected to a fused spur and then continues on to some sockets and a light?

where is the swa fed from?
what size is it 2.5 or 4mm by the looks of it.

A submain to a distribution board should not be fed from a spur off a socket ring.

I think (and I am making some guesses here) it is unlikely to be suitable to use the existing supply cable unless it is fed from its own breaker in the house DB.

yeah it comes from the MCB in the house, i believe its a 2.5mm just not sure how to extend it and make it so the cable can reach a higher point on the wall instead of replacing the whole cable

littlespark · Apr 22, 2024

What is the item on the left there?

I see the SWA coming into the box on the right... to a DP switch? (with fuse?) Load side of that to the double socket in the middle, then looped through to whatever is on the left.
I am presuming a switch/fuse with a 3A fuse to go up to lighting?

Having a consumer unit at that height could be preferable to being too high up on the wall. Could even make it lower... but a simple joint box low level, then come up in pvc conduit for mechanical protection into a DB... then out from there.
But it is a bit OTT to put in a db for a 2.5mm cable... possibly 20A or less supply... unless there are future plans to upgrade that cable back to the source.

James · Apr 22, 2024

realistically you are looking at a 25A supply to this consumer unit at absolute max.

unless you are intending to use the full 90degree rating of the cable and all the problems that could entail.

DPG · Apr 22, 2024

Adamstc222 said:
yeah it comes from the MCB in the house, i believe its a 2.5mm just not sure how to extend it and make it so the cable can reach a higher point on the wall instead of replacing the whole cable

If you aren't sure of how to extend the cable then this may be outside your expertise. Nothing wrong on knowing your limits.

However as other people have said, it doesn't seem wise to fit a consumer unit. Not because of the height - that could easily be sorted, but because you most likely haven't got a suitable feed for it.

davesparks · Apr 23, 2024

Adamstc222 said:
Yeah a Socket, they are looking to upgrade their garage so want a consumer unit out there

But why do they want a CU? That won't give them any more available power than they currently have.

As it is a 2.5mm SWA cable it is presumably a 20A circuit (25A is possible I guess but unusual) so adding a CU will just make it non-compliant from a selectivity point of view.