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Summer House / Office - MCB's and consumer unit help

Postby lifetimesmile » Mon Nov 26, 2007 8:13 am

Hi All,

I hope someone can help, I'm planning on running power to my summerhouse some details:

55-60meters away from the consumer unit
the power will have to be 2 computers, TV and hifi (i'm thinking 6 double sockets)
2 x five-foot twin Cat 2 fluorescent's
1 x 2.5 or 3kw heater

I'm thinking of using 10mm2 SWA from the house consumer unit to the summer house where i'm planning on putting another consumer unit (recommendations?) and from there run 1 x 32a MCB for the plugs, 1 x 6a MCB for the lights and another 32a MCB for the heater?

what should i put in the house consumer unit?

Hope this all made sense? Any advice would be appriciated

Many thanks in advanced
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Simply Build It

Postby kbrownie » Mon Nov 26, 2007 8:26 pm

Hi lifetimesmile,
Don't like to sound unhelpfull, but are you aware of Part P of the building Regs. If not I suggest you find out about this before you carry out this type of work. Have a look in doctors projects under Part P.
Regards and be safe
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Postby ericmark » Tue Nov 27, 2007 4:19 pm

10mm cable is 4.4mv/A/m so at 60 = 264mv/A giving a limit of 34.8 Amp so assuming the very shortest of runs in the outbuilding 32 Amp would be largest you could use. More likely 25 Amp to allow for volt drop within the outbuilding. In now needs three core SWA as it now needs a copper earth and it may have problems with earth loop impedance. To work this out I would need more information like type of supply. In short it is part P work and if you don't know answers you should not be doing the job. The paper work and calculations are hard enough when you know what your doing. Dig the hole and lay the cable but remember there are protection items to be laid over the cable and cable needs to be in sand and at a minimum depth etc. Since this is not my area I can't advise but to have to expose the cable again to prove compliance would I am sure be unwelcome work so get an electrician to act as clerk of the works and follow his advice.


Postby lifetimesmile » Tue Nov 27, 2007 9:18 pm

thanks eric good advice
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