Garage Conversion Power Supply

poolballboy · 6 Sep 2019

Good Evening all, I hope my post finds you well.

I am planning on converting my standalone garage into a holiday let. It will have a downstairs living room, 4 double sockets, a kitchen with electric oven and 5 double sockets, a boiler, 2 bedrooms each with 4 double sockets and two bathrooms. Each room will have LED ceiling downlights lights installed.

Currently the garage is feed from the house with 10mm armoured cable. With this conversion will I need to upgrade this cable and if so to what size? Also, will it be OK to run the new garage conversion fusebox off the house fusebox or will it need its own mains power supply?

Im just getting my head around the build before i start getting trades people involved. i will not be doing this work myself.

Thanks in advance

Andy

AndyPRK · 6 Sep 2019

People are always saying you can run a whole house off 10mm

So I guess,yes

EFLImpudence · 6 Sep 2019

They are, I do, you can and they do.

However, if it is not sufficient, then neither might your house supply be.
Preferably not from your CU.

How far is the cable run?

Two simultaneous electric showers might not be a good idea. What about heating?

poolballboy · 6 Sep 2019

Hi, thanks for the replies.

There will be a gas combi boiler for the showers and heating. Run is around 30m i would guess.

We might have to go with two electric showers depending on water pressure but hopefully not.

Andy

EFLImpudence · 6 Sep 2019

poolballboy said:
There will be a gas combi boiler for the showers and heating. Run is around 30m i would guess.

Ok. gas is good.

In that case the cable should be fine with 60A fuse at supply end.
https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
Volt drop just over lighting recommendation but that doesn't really matter.

Is it 3 core SWA? If only 2 you might need a 10mm² bond/earth cable to house or separate earth at garage.

We might have to go with two electric showers depending on water pressure but hopefully not.

Not advisable unless switched so only one at a time (even in the house).

chivers67 · 6 Sep 2019

Have you got a photograph of your Service Head/In coming cable supply & Fuse? Current Earthing Arrangement? Probably best it has a Henley block near it to feed the Garage with it's own Double Pole Isolator. There's nothing that looks large power wise unless of course you go down the electric shower route in which case you'll need to think about working out maximum demand

EFLImpudence · 6 Sep 2019

When using the calcuiator use SWA(2core) option otherwise it thinks it's 3 phase supply.

EFLImpudence · 6 Sep 2019

poolballboy · 7 Sep 2019

Thanks for the reply. I’ve added pictures of the incoming supply and the supply in the garage. Looking at it again, it might actually be 6mm armoured cable and not 10mm.

poolballboy · 7 Sep 2019

ericmark · 7 Sep 2019

This house has a 60A supply and there is a granny flat below main house with cooker, electric shower etc. And main house also electric shower, cooker etc. Heating is oil, it has it seems been this way for years, and one would think if the 60A fuse was to rupture then it would be replaced with a larger fuse, however just because it has not ruptured to date does not mean it will not rupture, people in holiday lets are not normally careful about how much power they use.

Some one will have to sign to say it's all OK. And only that person can say what is required, it is down to his professional opinion, it's not cut and dried, so select your electrician and ask him what he will allow.

SUNRAY · 5 May 2020

It looks like you have 2 supplies coming in there so definite potential for for a full size supply if needed.

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Garage Conversion Power Supply

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