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Discuss Help with three phase power in the Electrical Wiring, Theories and Regulations area at ElectrciansForums.co.uk.

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  1. gavin26
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    gavin26 Guest

    Hi I need some help with 3 phase wiring. I'm fairly confident I'm right but haven't done it since I was 18. Would I be right in saying that normal 3 phase power for sockets are wired in star and you should end up with 5 cables at each outlet? L1, L2, L3, N & E? With a 3 pole isolator for phases.Also do they have to be wired separately? Or can they be wired as radials?

    I've been asked to do some industrial work (which I don't normally do!) what sort of thinks do I look for in regards to sized of cables etc what is the formulas for cable calcs on three phase?

    I have a picture of the way I think they are wired but can't upload it because I haven't posted 5 times! Will upload once I can!

    Appreciate responses
     
  2. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    i think from your post you really ought to get someone with 3 phase experience to help you on this job. it's a lot more complex than just wiring up a radial with a few sockets.
     
  3. gavin26
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    gavin26 Guest

    So am I wrong in the way it's wired?
     
  4. bugsy
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    bugsy Guest

    1 What are the sockets to be used for
    2 What load on each socket

    Personally I would wire each outlet on seperate radial with a switched / isolated s/o (M.K. Commando range 16a - 125a ) but as Tel say's if your not sure ?
     
  5. trev
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    trev Regular EF Member

    I'm sorry mate but you're taking on work that you're not sure how to do. This is wrong no matter which way you dress it up.
     
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  6. gavin26
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    gavin26 Guest

    I have done 3 phase sockets as an apprentice but never been incharge of the design. I know it's different calcs to single phase etc. probably best getting somebody in with me then!
     
  7. i=p/u
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    i=p/u Trusted Advisor

    spead acrooss phases equally is no.1 or you neutral will carry tom much cureent.... BEWARE
     
  8. The Ranger
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    The Ranger Guest

    jesus some off you's need to chill out

    it's really not that hard but need a few bits of info

    what size sockets?
    how far is the cable run?
    how is the cable installed?
    grouped cables how many?
    proposed protective devices?
    ambient temperature?
     
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  9. trev
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    trev Regular EF Member

    Ranger you're right it's not that hard but if you didn't know that would you take a job on that required it?
     
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  10. The Ranger
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    The Ranger Guest


    we all learnt once!
     
  11. trev
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    trev Regular EF Member

    Under supervision
     
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  12. gavin26
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    gavin26 Guest

    Hi ranger thanks for response. I know what the guys are saying but would just like a head start. I will in the end hire someone with 3 phase experience.

    I couldn't tell you length of runs etc yet but it will more than likely be ran in conduit. Could you tell me the 3 phase formulas
     
  13. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    which is why i suggested he got some expert help with the job. it may be to power motors or other industrial equipment. get it wrong and you're in it up to the neck. apart from that, public liability insurance may not cover him for 3 phase.
     
  14. Knobhead
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    Knobhead Guest

    The formulas for what?
     
  15. i=p/u
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    i=p/u Trusted Advisor

    1.7 x cos o<i x pf
     
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