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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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  • 0

    HD 308 S2 applies to the colours of insulation over conductors for multicore cables for LV use.

    It does not specify which phase is connected to that core.

    The harmonized standard for identification is BS EN IEC 60445 - it is these days identical to IEC 60445, and has the same statement regarding assignment of BN, BK or GY to particular phases L1, L2 and L3.

    Only BS 7671 specifies the colour assignment for the phases (BN for L1, BK for L2 and GY for L3), in Table 51.

    The LV Switchgear and Controlgear Assemblies standard, BS EN 61439-1, only points to IEC 60445 - which as you say permits an option, so if it's not tied down in a Purchase Order or Contract or Specification, the manufacturer is able to comply with the standard with a different phase assignment to BS 7671.

  • 0 in reply to gkenyon

    Hello - thank you so much for your response, which is illuminating! In my case the installation and panel manufacturer reside in a CENELEC country but not the UK, making things tricky as BS 7671 will not apply there. But I understand the gist of your response - the IEC / CENELEC standards don't mandate the assignment between cores (L1, L2, L3) and colours - that's why the Internet tells me that the assignments L1=Brown, L2=Black & L3-Grey are "preferred" from an IEC viewpoint and only a National standard such as BS 7671 may make such an assignment mandatory. In our case, the labelling of cores is good / reasonable / unambiguous, however the 'as built' installation (Grey, Black, Brown) differs from the designers' drawing (Brown, Black, Grey) which is an immediate problem. I have the unenviable challenge of determining the best way forward ... which could be to seek re-wiring on all panels ($$$) or to get the 'as built' drawings changed. My gut feel, from a through-life safety and human factors viewpoint, is to demand the former ... but impact will be most unwelcome ... thanks again.

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  • 0 in reply to gkenyon

    Hello - thank you so much for your response, which is illuminating! In my case the installation and panel manufacturer reside in a CENELEC country but not the UK, making things tricky as BS 7671 will not apply there. But I understand the gist of your response - the IEC / CENELEC standards don't mandate the assignment between cores (L1, L2, L3) and colours - that's why the Internet tells me that the assignments L1=Brown, L2=Black & L3-Grey are "preferred" from an IEC viewpoint and only a National standard such as BS 7671 may make such an assignment mandatory. In our case, the labelling of cores is good / reasonable / unambiguous, however the 'as built' installation (Grey, Black, Brown) differs from the designers' drawing (Brown, Black, Grey) which is an immediate problem. I have the unenviable challenge of determining the best way forward ... which could be to seek re-wiring on all panels ($$$) or to get the 'as built' drawings changed. My gut feel, from a through-life safety and human factors viewpoint, is to demand the former ... but impact will be most unwelcome ... thanks again.

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