running power to an outbuilding


Postby chris_on_tour2002 » Fri Jan 18, 2008 3:08 pm

hi,

i'd like to run power to my workshop at the bottom of the garden, about 115 feet away from the house, 130 feet from the consumer unit. should point out that i am NOT planning to do the work myself but am trying to plan the best route etc before paying a professional.

there is no existing power, presumably i need 6mm cable to a dedicated mcb on the consumer unit. my bigger concern is the run of the cable. i have a concrete patio area that i'd rather not dig up. is there any kind of conduit or trunking that is permissable to run above ground? and if buried do i need armoured cable and how deep does it need to go?

thanks
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Postby ericmark » Fri Jan 18, 2008 5:30 pm

There is a difference between allowed and common sense. First easy bit if we work on 7000 watt or 30 amp then at 40 meters than 6mm² just over the top on volt drop but close enough to ignore. (9.4 instead of 9.2 allowed) With earth loop impedance at incomer of 0.2 you would expect about 0.55 at the shed you need about 1.5 so that is also well within what you require. 522-06-03 Buried cables at sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground. SWA does not need to be as deep as concentric I think about ½ a meter is norm but can’t find my book. It is common to run cable along boundary fences visible as to if this complies with regulations I am not sure. The overhead cables have set heights but all this is contained in the “On Site Guide to 16th Editionâ€
ericmark

Postby kbrownie » Fri Jan 18, 2008 6:52 pm

Hi chris_on_tour2002,
Just to add some points and fill in alittle on eric's reply. Cable depth if buried is by general rule 500mm, if heavy digging i.e. Veg patch is in this area then increased to 600mm. Advised marker tapes and coping stones laid over cable for added mechanical protection, a record of cable route should be made and kept. Recommended cable SWA
You can install above ground but cables must be permently fixed and at a reasonable height above the ground level also needs mechanical protection and protection from sunlight and moisture. You can use PVC/PVC for this and conduit. The installation must be RCD protected
plus disconnection times should be reduced.
Remember Part P complies to this installation and your electrician will give you more detailed info.
Hope info of help
KB
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