Three phase wiring

  1. smashweld Member

    Messages:
    514
    Location:
    Central Scotland
    Looking for some advice....

    This folder was connected with a 4 pin plug using SWA cable, and a seperate earth wire going to an earth block on the fuseboard....the SWA was/is connected at the junction box end but just taped up at the plug end. The red, yellow and blue were connected to L1,2,3 at the plug...the black wire connected to the earth pin (assumed it was neutral at first with a 'custom' plug/socket...) but can see it connected to other earths with a green/yellow sleeve over it in the bottom right of junction box.
    So the socket that was being used would have just been the 3 lives and an earth, no neutral in use?

    the seperate earth wire had me wondering...was it probably an alternative to using the SWA armor or 'belts n braces'? fairly sure the earths in the junction box aren't isolated from the rest of the body

    anyway...main thing is I want to connect it for now using 5 core cable and a 5 pin plug...what's best to do with the unused core and the neutral pin on the plug?
    IMG_2210.JPG IMG_2230.JPG

    thanks
     
  2. brightspark

    brightspark Member

    Messages:
    25,744
    Location:
    yarm
    they have just bonded the outer armoured at the control box and ran a separate earth to it and cut the outer armour off in the plug and taped it .what type cable are you going to use on it and I take it it doesn't require a neutral ??just the 3 lives
     
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  3. Robotstar5

    Robotstar5 Casanunda Staff Member

    Messages:
    17,485
    Location:
    Birmingham
    Connect all the cores (correctly) in the plug then at the panel end put the neutral into a spare/unused terminal on the DIN rail.
     
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  4. Woody.v8

    Woody.v8 Blue gluer

    Messages:
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    Location:
    staffs
    A neutral is always handy on a machine anyway if you need a convenient 240v , with rcds now you can't pinch one from anywhere else ( not that you would ) :whistle:
     
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  5. smashweld Member

    Messages:
    514
    Location:
    Central Scotland
    using 2.5mm 5 core SY cable as an extension..
    just temporary but for now I want to leave the SWA connected to the machine and join the SY cable with blocks (next to the wall...out the road)....so everything wired up as 5 core but nothing connected on the machine side of the neutral block?
     
  6. Woody.v8

    Woody.v8 Blue gluer

    Messages:
    2,891
    Location:
    staffs
    You can use sy cable to wire in permanent if you want it doesn't have to be swa , yeah just blank off the neutral at the machine end.
     
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  7. brightspark

    brightspark Member

    Messages:
    25,744
    Location:
    yarm
    as above its quicker and better just to wire it directly in to the machine
     
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  8. smashweld Member

    Messages:
    514
    Location:
    Central Scotland
    I thought about that but wasn't sure on this seperate earth cable tbh, why it's needed?...would need to get that in to the junction box if it's needed

    in a previous life the SWA armor would have been the equivalent of the seperate wire now attached to the body? I'll need to look properly but are junction boxes usually isolated from the body?
     
  9. brightspark

    brightspark Member

    Messages:
    25,744
    Location:
    yarm
    the only reason to run a separate earth wire is it was wired in to a plug with armoured and you wouldn't be able to use the Brading as an earth wire without a gland . a bodge really .if anyone's running a separate earth for an armoured it is supposed to be run parallel alongside the cable not willynilly running of in different directions tapped on to wherever :)
     
  10. Ton-up

    Ton-up Member

    Messages:
    1,245
    Location:
    Essex, England.
    Have you got the correct size cable as that cable doesn't look quite large enough to me either.
     
  11. smashweld Member

    Messages:
    514
    Location:
    Central Scotland
    the cables in the pic is how it came...about 5.5kw max with both motors running..

    the seperate earth was cable tied to the SWA, it was a plug/socket but never unplugged.....eventually want it hardwired in with the SWA once there's a proper supply to the workshop, just seemed easier connecting up with choc blocks just now..
     
  12. hotponyshoes Member

    Messages:
    913
    Location:
    Somerset. Uk
    Not exactly sure what you are talking about but some people wire any un-used cores in a cable to the earth at the plug end.
    We see it a lot on generator installs for mobile setups (marquee hire etc)

    I think the idea is that if a cable gets damaged you have less chance of the spare core/s becoming live as they should trip out
     
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  13. dobbslc

    dobbslc Member

    Messages:
    3,850
    Location:
    Hertfordshire UK
    ^^^ you are meant to terminate any spare core to earth, it stops induced voltage in that core. I've measured over 50v AC on cores that weren't grounded.
     
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  14. brightspark

    brightspark Member

    Messages:
    25,744
    Location:
    yarm
    and when earth wires come adrift in lighting circuits even if there isn't any faults 50v is about the norm for induced current and you certainly feel it when touched :laughing:
     
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  15. smashweld Member

    Messages:
    514
    Location:
    Central Scotland
    Just had a proper look....the separate earth wire and the black wire in the SWA are both connected to the full body of the machine...just at different points. Is it just the wire in the SWA would be too small on its own?

    Also...good to see two different ways to deal with this extra core when you”re unsure :p
     
  16. brightspark

    brightspark Member

    Messages:
    25,744
    Location:
    yarm
    the majority of time the swa is sufficient to use as the earth and does not need a separate earth running. here's some info and tables. the ones in red aren't suitable https://gadsolutions.biz/regulations/swa-as-the-cpc on small cables generaly single phase up to 6.0mm there is hardly any difference in price so would use 3 core 1 as the earth any bigger just use 2 core because the price rockets :laughing:
     
  17. rtbcomp

    rtbcomp Moderator Staff Member

    Messages:
    18,471
    Location:
    Sheffield UK
    One of my customers left an earth floating inside a consumer unit, it intermittently touched a live and blew the computer network and made the kettle live. It only came to light after I network their two computers and I got the blame.:mad:
     
  18. smashweld Member

    Messages:
    514
    Location:
    Central Scotland
    Aha, so the need for the earth wire in the junction box AND using the SWA is a regulation thing
     
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