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  1. #1
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    Electrical query: Looking for some help advice.

    I'm currently looking at building a shed/workshop in my garden and I'm going to need to supply some electrical power.
    This needs to be run from the main supply board in the garage which will be a run of about 40meters.
    Obviously I need to run an armored cable but what size do I need?

    Also how deep do I need to bury it? Best I can find so far is 3/4 meter. Does this sound correct?

    Any help gratefully received.

  2. #2
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    May 2004
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    Finchampstead, Berkshire, UK.
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    6mm will give you 32Amps over that distance.
    Buried to a “safe depth”

    Jim
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  3. #3
    Join Date
    Jan 2006
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    Chelmsford Essex
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    942
    Quite correct at look at armored cable but also consider a thicker cable if you decide you want to do any welding in the future. Depending on your earthing I would always run 16mm three core SWA. The time and enough is digging so put in a good cable. Usually your local electrical wholesalers will give you a good price as shipping can be costly due to the weight.

  4. #4
    Join Date
    Feb 2007
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    West Sussex
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    8,632
    when i had elect power put into my garage i had to dig a trench from the house to the garage that was at least 18" / 0.5m deep I think (it was 5 years ago), at all points which the armoured cable was laid into.
    I was told it needs to be deep enough to avoid a rotovator blade and then a bit more for safety.

    This all went to a fused switchboard that could be expanded later.

    May be useful:
    https://www.cablejoints.co.uk/upload...ance_Notes.pdf
    https://www.familyhandyman.com/elect...rground-cable/
    https://professional-electrician.com...ations-garden/


    - regs may have changed, so worth checking with professional bodies.
    Last edited by KevinW; 29-08-19 at 08:18 AM.
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  5. #5
    Join Date
    Jan 2002
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    Reading, Berks, UK.
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    BS 7671 regs, Table 4D4A, 10mm 3 core buried 67A, 16mm 3 core 89A buried.
    Anything over 4mm we always use a 3 core, one for earth as the SWA can get a bit sketchy on long runs for the earth.

    600 buried depth with a cable indicator tape laid over. If you are worried someone might dig into it then easy way is just lay some roofing tiles over it before burying.

  6. #6
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    Thanks all. Good info there.
    Initially I'll only be using low power kit in there but as you don't ever know what the future holds would rather have it as big as practical so I'll have to decide between 10mm & 16mm.

    Just to clarify when a cable is described as 10mm am I correct in assuming this is the cross sectional area of each core so for 10mm this would be around 3.6mm diameter (16 would be 4.5)?
    I'll pay a professional to wire into my existing supply and the distribution in the shed but don't see the point in paying good money for someone to dig a trench!

    Good call about putting something solid over the top better to be safe.

  7. #7
    Join Date
    Jan 2002
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    Reading, Berks, UK.
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    Quote Originally Posted by GDCobra View Post
    Thanks all. Good info there.
    Initially I'll only be using low power kit in there but as you don't ever know what the future holds would rather have it as big as practical so I'll have to decide between 10mm & 16mm.

    Just to clarify when a cable is described as 10mm am I correct in assuming this is the cross sectional area of each core so for 10mm this would be around 3.6mm diameter (16 would be 4.5)?
    I'll pay a professional to wire into my existing supply and the distribution in the shed but don't see the point in paying good money for someone to dig a trench!

    Good call about putting something solid over the top better to be safe.
    The 10mm is the CSA of the conductor, in this case 10mm.
    If you want to know the complete O/D I will have to go and measure some, or have a look on line, think there are some reference charts there.

  8. #8
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    Quote Originally Posted by Bigblock View Post
    The 10mm is the CSA of the conductor, in this case 10mm.
    If you want to know the complete O/D I will have to go and measure some, or have a look on line, think there are some reference charts there.
    Thanks Bigblock, if my math's is correct (no guarantee of that!) for a CSA of 10mm I calculate the core diameter will be 3.6mm to package 3 in a single cable with a bit of insulation and armour I'm expecting arount 10-12mm, That sounds about the same (maybe smaller) than I used for a similar job at the last house. But as I say that depends on my math's.

  9. #9
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    Quote Originally Posted by GDCobra View Post
    Thanks Bigblock, if my math's is correct (no guarantee of that!) for a CSA of 10mm I calculate the core diameter will be 3.6mm to package 3 in a single cable with a bit of insulation and armour I'm expecting arount 10-12mm, That sounds about the same (maybe smaller) than I used for a similar job at the last house. But as I say that depends on my math's.
    Used to say 10mm 3 core & 16mm 3 core, thin thumb and thick thumb.
    In the dark old days pre mobile phones, internet, even pre battery drills.

  10. #10
    Join Date
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    Quote Originally Posted by Bigblock View Post
    Used to say 10mm 3 core & 16mm 3 core, thin thumb and thick thumb.
    In the dark old days pre mobile phones, internet, even pre battery drills.
    Sounds about right although both of my thumbs are about the same thickness! Maybe should be 10mm = Thumb, 16mm = Big toe

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