power to shed and connecting garage


Postby armytouch » Mon Jan 14, 2008 2:25 am

hi. please can you give some advice. I have just moved into house and the electrics where done approx 3 yrs ago,new consumer unit installed.RCDS included,but all MCBs are been used. The brickshed which is adjoining the house and covered as been supplied from an existing socket on 2.5mm cable through to another 2 sockets then to a switched fuse spur to a light.
What i would like to do is place a garage consumer unit in the shed to run about 3-4 sockets and about 2 lights with a light switch on the outside wall,which is covered.
A few questions,could i use the existing 2.5mm cable from the existing socket to the garage consumer unit as the mains power in?
I was told i need to use 6mm cable to garage consumer unit is this true and if so where would i get the mains power to garage consumer unit from if not an existing socket and could i connect 6mm cable from a socket?
Can i connect the main consumer unit straight to a garage unit,if so which size cable would i need to use 6mm,2.5mm or any other?
What size MCB breaker would i need to fit into main consumer unit for garage consumer unit?
cheers for your help.
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Postby ericmark » Mon Jan 14, 2008 9:50 am

Size of MCB in main consumer unit will depend what you intend to run in the garage but one would normally be looking at a 32 amp. The cable size would depend on distance and MCB size but normally about 6mm². Although you could supply from the ring main this is not recommended as to how without seeing what you already have can't really answer. There is also the question of Part P unless you live in Scotland. So really since you need an electrician unless in Scotland you need to really ask him for advice.
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Postby armytouch » Mon Jan 14, 2008 11:47 am

So if i install a 32a circuit breaker into main consumer unit,run a 6mm cable from there into a garage unit,i can run a 6a lighting circuit on 1.5 mm cable and 16a socket circuit. The distance from main unit to garage unit is about 8m at the most.
cheers
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Postby ericmark » Mon Jan 14, 2008 5:37 pm

Part P permitting yes. But remember we are not on site and there may be something you have failed to mention. Always best to get advise form someone on site. If your not in Scotland it may be cheaper to get a firm to do the job than pay the fees for Part P. And even if you pay fees they may not accept your signature on paper work. Check first what your building controls will allow.
ericmark

Postby stevenc1603 » Tue Jan 15, 2008 4:57 pm

I have done pretty much what you are talking about doing although mine was to a small summer house not the garage.

I used a 10mm2 steel wire armour cable to run from the house consumer unit underground to the summer house. Now I never plan on using the maximum current that can be drawn on 10mm2 cable, but I like having the extra safety margin.

Its connected to a 32a MCB on the RCD side of the house CU and I have a 2 circuit "garage" CU on the other end with a 32A ring main and a 6A lighting circuit. I used 1.5mm2 for the light and 2.5mm2 for the ring.

As eric has mentioned, if your in England/Wales, you really need to get someone in to give advice as the regulations down there are much stiffer than they are up here in Scotland.

I had my sparky do the connection at the house end to make sure everything was OK too.
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Postby armytouch » Wed Jan 16, 2008 12:54 am

Hi again,cheers for all your help.
I dont need to bury cable or use armour casing because it not running externally the brick shed adjoins the house so lucky there. If there wasnt any room to install another breaker in the main consumer unit how could i still provide power to a garage consumer unit to run 16a sockets and 6a lighting circuit,thanks again.
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Postby tinomclaren » Fri Jan 18, 2008 3:13 pm

You will need to put in a larger consumer unit in your house do acheive this or have mains into the main consumer unit split (before it) and then feed the 2nd consumer unit, this then becomes quite a big job and only an electrician should do it.

I would suggest extending your downstairs ring into your garage and your garage light extented to your downstairs lighting ring.

I would, however, get an electrician to come and evaluate this situation for you as extending the rings will only be possible if your load is not too high in the garage and you would be extending the 'ring' not just adding a spur.

If your using the garage mains for jet washer, drill etc.. then this would be OK but if your using it as a workshop with higher loads then you will need a option 1 above, get a spark to tell you what to do.

Dont forget, you must consider cable runs too.

Remember, be safe, if in doubt get a spark to advise you or even do the work, as you will need the required paper work at some point.

Regards

Tino
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