Is it safe to supply a single phase machine from a 3 phase 5 pin commando socket?

The socket rating is ok (32A, FLA of machine is 24A), but current would only be drawn on one phase

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  • What danger do you envisage might occur?

    One thing to check is whether the equipment manufacturer has a specific overcurrent protective device rating (some German machines, for example, specify 25 A, which can be tricky in the UK.

    And of course, if using a socket-outlet rated up to 32 A, is the outlet RCD protected in line with Regulation 411.3.3?

  • Thank you for the note about specific over current protective device rating.

    I was wondering if there would be a danger associated with the loads being unbalanced for the 3 phase breaker supplying the socket.

  • That can be a rub ... in our machineshop, all the CNCs machines were connected thru 32A TPN ceeforms. This made changes easy & isolation quick and obvious. When the space was refurbished we had to remove & hardwire because of the RCD rule - try getting a 30mA RCD to hold with a CNC that contains several VFDs

  • As others have said, its fine. If the RCD thing is a problem and there is no local appetite for documented deviations then one can sidestep it by using a 63A socket on a supply limited by 25A MCB or whatever. Not perhaps the intention of the regs and a bit of a waste of space but not a fail either.

    If you have lots of 3 phase plugs with single phase loads, it is helpful to vary the phases around so loads are not  all on phase 1.. . If you like to know which phase then a stripe of tape of the phase colour on the plug serves as a reminder.

    Also in the world of temporary wiring,  3 phase plugs with 3 tails emerging each with a single phase socket or strip of sockets is a common thing, although the glanding no longer meets the IP 44.

    Mike

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  • As others have said, its fine. If the RCD thing is a problem and there is no local appetite for documented deviations then one can sidestep it by using a 63A socket on a supply limited by 25A MCB or whatever. Not perhaps the intention of the regs and a bit of a waste of space but not a fail either.

    If you have lots of 3 phase plugs with single phase loads, it is helpful to vary the phases around so loads are not  all on phase 1.. . If you like to know which phase then a stripe of tape of the phase colour on the plug serves as a reminder.

    Also in the world of temporary wiring,  3 phase plugs with 3 tails emerging each with a single phase socket or strip of sockets is a common thing, although the glanding no longer meets the IP 44.

    Mike

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