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Three Phase AC Phase Conductor Colours - Mandatory?

Fraser Donachie

An LV Switchgear manufacturer has correctly used Brown, Black and Grey conductor colours in their panels. But the assignment is not the "preferred" L1=Brown, L2=Black & L3=Grey. Instead, the phase sequence is different. Whilst this is extremely undesirable from a safety and human factors viewpoint, is it 'illegal' or would it mean their DofC is invalid? IEC 60445 does not specify the assignment between L1, L2 & L3 and Brown, Black or Grey. I believe CENELEC HD 308 S2 may specify the "preferred" assignment but I cannot obtain a copy of that. How mandatory is the "preferred" and generally accepted assignment L1=Brown, L2=Black & L3=Grey? THANKS!

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    I have just been reading 514 in the regs, and I think it is probably rather misleading. I think that its connection of L1..3 as labels to colours needs very careful explanation. In the table 51, these are connected as cable identifications only, in other words L1 as a cable marker is interchangable with brown as a cable colour. Many accessories and products for 3 phase equipment are labeled on terminals with L1, L2, and L3, and perhaps N, which seems to imply with 514 that only a brown wire should be connected to L1 etc. There is no logical or operational requirment as to why this needs to be true, although it may be used on wiring drawings or schedules to ensure correct wiring. Lots of items, such as rotary switches avoid this ambiguity by numbering the terminals, and wiring schedules for panels or similar simply say brown wire (Br) connected to item 1 terminal 8 and item 2 terminal 6.

    Idealy I suggest thet L1..3 is ONLY used as wire identification of wires with other sheath colours, and not as indicators of actual connections on other items. Some items such as motors have markings of W1..6, others have the illogical L1..6! I feel that this has been missed in the IEC and BS7671 standards, and we have ended up with all manner of terminal designations that can be confusing. It has also caused this thread!

  • 0 in reply to David Stone
    David Stone said:
    Many accessories and products for 3 phase equipment are labeled on terminals with L1, L2, and L3, and perhaps N,

    Shouldn't terminals on three-phase equipment be labelled "U", "V" and "W" in accordance with BS EN IEC 60445, to avoid this confusion?

    This isn't new, by the way !

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  • 0 in reply to David Stone
    David Stone said:
    Many accessories and products for 3 phase equipment are labeled on terminals with L1, L2, and L3, and perhaps N,

    Shouldn't terminals on three-phase equipment be labelled "U", "V" and "W" in accordance with BS EN IEC 60445, to avoid this confusion?

    This isn't new, by the way !

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