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Thread: Running power to a shed (2 core/3 core + RCD?)

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    ALT0153™ Rob_B's Avatar
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    Question Running power to a shed (2 core/3 core + RCD?)

    Hi folks,

    I'm trying to run power for a tumble drier to a shed, I need approx 15m of cable.
    Previously in the old shed I had a few metres of extension plugged into a normal socket that went out to a twin socket (setup by previous owner)

    I bought a 15m 'garden' extension for lawnmowers with the intention of cutting off the twin end it has and and just wiring up the 3 pin socket I have however the cable is only twin core (do lawnmowers only need 2 core?!)

    Does anyone have suggestions on options? Do I need to get myself some 3 core (if so how thick?) or can I use the 2core with an RCD socket at the house end?

    All suggestions more than welcome as we've been without a tumbler for months and my house looks like a washhouse!

    Thanks,

    Rob

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    The late but legendary peterb - Onward and Upward peterb's Avatar
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    Re: Running power to a shed (2 core/3 core + RCD?)

    A lawn mower has power rating of typically 500W or less - about 2 amps. Your tumble drier will be at least 1K, possibly up to 3KW - 12 amps. However, if you are wiring in a 13 Amp socket, you ned the cable to be capable of carrying 13A - so minimum of 2.5m^2. If you are putting in a double gang socket, you could potentially draw 26 amps - so 4m^2 cable.

    Cable ratings for twin and earth are here. http://www.cable-ratings.co.uk

    Are you running it underground? If so, you either need to run it in conduit (you could use 20mm plastic tube) or better still, armoured cable - twin core using the armour as the earth conductor. You will need proper terminations to ensure the integrity of the earth bond.

    If you are running it along an external wall, you still need conduit or an armoured cable to protect the cables from mechanical damage. If it is an internal wall, it can be clipped direct, which would enable you to get away with running 2.5mm^2 cable to a double gang socket - but I would urge you not to "just get away with it" - especially as the work comes under the scope of building regulations as it is an outbuilding.

    If your house is already protected by an RCCB, you don't need to add another one, although it would be a sensible move, especially if you are planning to use the power for for tools or to plug in a lawn mower.

    You also need to consider how you are going to tap into your house mains. Again, ideally you need a dedicated circuit breaker in the fuse box (which could also be the RCCD device). Otherwise you need to spur off a convenient point off a ring main. If you are only going to power one socket, you could use a socket with a built in RCCB.

    You can find Part P of the building regs here. Section 2.2 refers to garages and outbuildings, so you should comply with part P entirely.

    http://www.planningportal.gov.uk/upl..._AD_P_2013.pdf

    (A lawn mower doesn't need an earth if the motor is double insulated. Your tumble drier won't be - it needs an earth!)

    If you are running a temporary extension that you only run out when you use the drier, then part P doesn't apply and life becomes easier. You could use this http://cpc.farnell.com/pro-elec/2315...5m/dp/PL09479- but make sure it is fully unwound before use.

    or this http://cpc.farnell.com/smj-electrica...win/dp/PL11550

    Or this

    http://www.diy.com/nav/fix/electrica...skuId=11039646

    Personally, I'd go for one of the first two from CPC
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    Rob_B (16-06-2014)

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    ALT0153™ Rob_B's Avatar
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    Re: Running power to a shed (2 core/3 core + RCD?)

    Thanks Peter, too much to take in for me at nearly midnight but I get the idea and will reread tomorrow!

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