Attached garage supply - again!

[Johnboy84]

Hello all. Firstly thank you for a great source of really useful info. I've been refurbing my house almost everyday since i bought it 18 months ago and this is my first post - testament to the great quality posts!! Anyway, enough sucking up!!! I've searched the previous posts on garage power supply but most of the results relate to detached garages requiring armoured cable running across the garden etc.

I am nearing the end of building an attached garage on the side of my detached house. It is a complete selfbuild so I get regular visits from the building inspector so he will ultimately be verifying my electrical works as part of the build. I am working 9-5 for the next 3 weeks so wont be able to get him out for advice and the first fix wiring is now holding me up so i'd like to get on with it in the coming evenings.



I will be using the garage for general DIY so will fit about 10 double sockets around (to save long extension lead runs) but I tend to work on my own so peak power consumption is likely to be from only two plugs at a time (inspection lamp + 1x power tool) - ie not several heavy draw items simultaneously switched on.


I have bought a 4 way garage CU with 2x MCB (6amp and 30 amp) and a RCD.

So my question ...

1) Should I run a dedicated power supply from the house CU to this garage CU?

2) Should I extend the downstairs ring main into the garage CU then come off the garage CU from there as a separate ring?

3) Should I not use my 4 way garage CU and just extend the downstairs ring main and treat the garage as a 'normal' room?

4) or am I way off track and do some thing different??

Thanks again. I welcome your suggestions with open arms.

Cheers, John.

 

[Aragorn84]

I dont think you'd be allowed to do (2) at all.

(1) sounds like the most sensible option imo.

You could do (3) and extend the lighting and ring main from the property into the garage, but (1) means only running 1 cable, whereas (3) means running at least 3 and also having to find suitable places to break into the ring and lighting circuits and then you have the hassle of joining them in an acceptable manner.

 

[ban-all-sheds]

4) Split the tails after the meter and supply the garage CU separately. Depending on the distance between meter and CU you may need to install a switchfuse - the limit varies between DNOs, but it's usually 3m.

 

[holmslaw]

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[ban-all-sheds]

1) Which regulation requires a single point of isolation?

2) If it bothers you that much then fit an isolator before the split.

 

[holmslaw]

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[ban-all-sheds]

537.1.4

Main switch in the garage CU. Or the switchfuse.

It does'nt bother me at all.

So why did you post?

And then use this to feed the switchfuse that you suggested? - you're havin a larf. All you will achieve is totally unnecessary additional costs for absolutely no purpiose what so ever.

I wish you'd make your mind up - first you claim that a single point of isolation is required, now you're saying that no purpose whatsoever would be served by installing one.

Johnboy84, stick with your option 1.

That's one option, and it is quite commonly done.

My #4 is also a valid option.

 

[londonboy]

Personally option one.

Run armoured through to garage.

 

[barcelona]

4) Split the tails after the meter and supply the garage CU separately. Depending on the distance between meter and CU you may need to install a switchfuse - the limit varies between DNOs, but it's usually 3m.

Sorry to interrupt, but why wasn't I advised to split the meter tails and have a separate supply ?. Which way is best ?.

 

[electronicsuk]

4) Split the tails after the meter and supply the garage CU separately. Depending on the distance between meter and CU you may need to install a switchfuse - the limit varies between DNOs, but it's usually 3m.

Sorry to interrupt, but why wasn't I advised to split the meter tails and have a separate supply ?. Which way is best ?.

The only reason to split the tails would be lack of spare ways in existing CU or high expected load in the garage, neither of which seems to apply here. The cheapest and easiest option is for you to use a spare way in the main house CU.

 

[barcelona]

4) Split the tails after the meter and supply the garage CU separately. Depending on the distance between meter and CU you may need to install a switchfuse - the limit varies between DNOs, but it's usually 3m.

Sorry to interrupt, but why wasn't I advised to split the meter tails and have a separate supply ?. Which way is best ?.

The only reason to split the tails would be lack of spare ways in existing CU or high expected load in the garage, neither of which seems to apply here. The cheapest and easiest option is for you to use a spare way in the main house CU.

Thanks.

 

[holmslaw]

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[RF Lighting]

Make that five votes for option 1

 

[ban-all-sheds]

The only reason to split the tails would be lack of spare ways in existing CU or high expected load in the garage, neither of which seems to apply here.

Or you just think it's more elegant to have all your CUs at the same hierarchical level.

Or your house CU has no non-RCD protected ways, and you don't want to lose house circuits through garage faults.

 

[holmslaw]

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