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Discuss Cable calculation in the Commercial Electrical Talk area at ElectrciansForums.co.uk.

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  1. Simon Burton
    Offline

    Simon Burton Active EF Member

    Location:
    West Midlands
    Business Name:
    RSB Electrical Services
    Il give you the scenario, stables in a field, e-on have been out and put a supply in a hut with a meter on and a one shot, main fuse is 80amps, the customer need a fuseboard putting in the barn, 75metres away, what size cable would i be looking at, ive done a calculation, 1 x swa cable 3 core, burried, ive use 80amp as the demand as this is the maximum at the origin and the cable size is coming back at 25mm. Is the right or is there some sort of diversity applied which would allow you todrop to 16mm. All that will be going in are sockets and light, quite a few to be fair but altimatley just wanted to get the armoures cable to the fuseboard and just questioning the size. Any help is appreciated
     
  2. Sintra
    Offline

    Sintra The Innkeeper Staff Member Admin

    Location:
    Belfast/London
    Work it out allowing for 3% voltage drop on the lighting.
     
    • Agree Agree x 1
  3. westward10
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    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Location:
    Northamptonshire
    Your calculations are incorrect.
     
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  4. westward10
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    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Location:
    Northamptonshire
    Appendix 4 Reg 6.4 gives permitted vd limits. These limits apply from the origin of the installation to any load points and for lighting this is 3% therefore, if you have a 3% allowance on your submain any lighting circuit is going to exceed this if the submain is operating at full load, not likely. It is often quoted submains feeding lighting and power has a vd limit of 1% allowing a small allowance for the lighting.
     
    • Like Like x 1
  5. Strima
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    Strima Electrician's Arms

    Location:
    St Neots
    What’s you design load and max demand? Earthing arrangement? Any utilities that require bonding?
     
  6. Pete999
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    Pete999 Forum Mentor

    Location:
    Northampton
    Business Name:
    None
    The hut you talk of does it require any bonding?
     
  7. Spoon
    Offline

    Spoon Forum Mentor

    Location:
    Lancashire
    When you say "is coming back" is this your own cals or have you inputted the info into a web site?
    As above. Your calcs are incorrect.
     
  8. westward10
    Offline

    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Location:
    Northamptonshire
    He is quoting a three core and hence with an 80A head the third core should be adequate for bonding purposes.
     
  9. westward10
    Offline

    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Location:
    Northamptonshire
    If you allow for a 1% drop that is a hefty cable.
     
  10. Pete999
    Offline

    Pete999 Forum Mentor

    Location:
    Northampton
    Business Name:
    None
    Maybe , he may not know that he can use the armour as a cpc, after all he is asking questions that an electrician should know the answer to, don't you think, probably not though.
     
    • Agree Agree x 1
  11. bill01803
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    bill01803 Regular EF Member

    Location:
    Devon
    At 80m and 80A I get 50mm
     
  12. Vortigern
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    Vortigern Regular EF Member

    Location:
    England
    Business Name:
    F.H. Electrical
    25mm at 63a
     
  13. Simon Burton
    Offline

    Simon Burton Active EF Member

    Location:
    West Midlands
    Business Name:
    RSB Electrical Services
    In what way.
     
  14. westward10
    Offline

    westward10 In echoed steps I walk across an empty dream. Staff Member Moderator

    Location:
    Northamptonshire
    Reconsider your volt drop you have used 5%
     
  15. Simon Burton
    Offline

    Simon Burton Active EF Member

    Location:
    West Midlands
    Business Name:
    RSB Electrical Services
    I dont know the design current so im taking it as 80amps, as thats is the fuse rating on the head.
     
    • Dislike Dislike x 1
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