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60 amp single pahese 240 volt AC supply (UK)

Discussion in 'Electronic Basics' started by Chris, Nov 25, 2005.

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  1. Chris

    Chris Guest

    I have bought a TIG welder that will run off UK 240 volt single phase 50
    hertz AC supply, but on full power can draw up to 50 amps. I want to wire
    this off the house incoming mains distribution board, to a spur in my
    worksshop, about 30 feet away. The mains supply from the road is on a 100
    amp fuse to the meter. The meter then feeds straight to a fuse switch with
    an 80 amp fuse in it. If I can get an extra pair of tails into the outlest
    of this switch fuse i was going to run armoured cable to a 60 amp switch
    fuse in the workshop, with the welder hard wired into that. Can anyone see
    a problem with this? I live in the sticks, and although the mains is fused
    100 amp the incoming armoured cable form the pole looks quite thin...

    What core size armoured do I need to be looking at? BTW, a pic of the
    welder load plate is at

  2. Don't know about UK standards. Here (USA) we use the National Electric Code
    and if one modifies an installation without permitting and inspection, dire
    consequences can result ... as one example the refusal of an insurer to pay
    for damages ignited or initiated by an electrical fault.

    For 50 amps, one needs robust wiring (# 8 copper or # 6 ... depends on
    several factors). Also, the sub-feed must be protected with an over-current
    device properly sized to the wire size and the particulars of the load the
    installation. The means of disconnect might also be regulated ... even the
    location of the disconnect device. It can get complicated. Conduit might
    be required, for example.

    Don't rush into this. Check with your local authorities. You might need a
    permit and an inspection after installation to make it legal and to avoid
    future problems.
  3. pebe

    pebe Guest

    I would agree with Charles. Give your local electricity board a ring
    They will give you a definitive answer
  4. Fermi

    Fermi Guest

    This should be OK. You'll need a 50A MCB in the distribution board and
    cable with 8mm^2 or 10mm^2 cables.

    I'm not sure what you mean by "a fuse switch". Is this separate to the
    distibution board? I've seen some installations where the tails from the
    meter go to a switch which then supplies two distibution boards (in the
    case where the first distibution board didn't have enough connections).

    Anything after the meter is your responsibility. The meter and the
    distibution head (which has the 100A fuse) is property of the supplier (the
    fuse just protects their system should there be a fault on your property,
    it doesn't really increase safety).

    The key points are:
    The cable to the workshop must be rated for the application .Different
    cables will have different ratings depending on whether they are clipped to
    the surface of a wall or if they are enclosed in the wall or in conduit
    (where they are derated due to decreased ventilation).
    The cable must be protected by a circuit breaker (MCB) or fuse. This
    prevents the cable from overheating so the cable must have higher rating
    than the fuse/MCB that protects it. If the "fuse switch" is connected
    directly to the meter and you run cables from this you will neeed something
    like 16mm^2 or 25mm^2 cable as the only thing protecting the cable will be
    the 100A fuse.

    Your local library (if one exists) on town/city library may have a copy of
    the IEE 16th edition wiring regulations:

    The work you are intending to do falls under the new Part-P building
    regulations and will need approval from the local building inspector:

    Various examples of distibution boards and cable:
  5. 50 Amps on a two phase 240V mains looks a lot to me.

    Is this really a 12kW single phase welding device?
  6. It's approaching the limit of the typical company fuse. I guess he'll
    be okay if there's nothing else switched on at the same time. ;-)
  7. Damn! I'll have to rip out the distribution board I renewed 5 years
    ago, then.
  8. [...]

    Wrong newsgroup! Try posting this to uk.d-i-y as there are plenty of
    qualified electricians there who will assist you to do this within the
    UK wiring regs.
  9. Paul Blitz

    Paul Blitz Guest

    Bear in mind that, in the UK, new regulations mean that unless formally
    qualified, you can NOT do electrical work in your own house, you MUST get an
    approved electrician to do the work.

  10. Chris

    Chris Guest


    Sorry for delay in replying, been away (I haven't blown myself up yet...
    :)) really good links and info, I have bought a 60 amp fused switch and
    will get an electrician to split the meter supply tails to feed two
    switches, the original to the house distribution board, and the new one
    serving just the welder down an armored cable to the workshop, with an
    isolation switch at that end. I think that should cover things? Thanks
    again for all the advice!
  11. Rich Grise

    Rich Grise Guest

    Thanks for coming back with a progress report; the fact that it's a report
    of success is kinda like icing on the cake, so to speak. :)

  12. Terry

    Terry Guest

    No the original poster said 'single phase'!
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