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Three Phase Power and Cross Phasing


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Are there rules over whether or not having two or more phases on a lighting bar is allowed? I've been to various venues; some are relaxed about keeping phases apart and some are really strict. Is there a law governing it?
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This was a requirement in the 14th Edition regs (IIRC - may have been 13th)


However, the 16th (lastest) edition of the IEE electrical regulations has relaxed this requirement.


That said -

You may not be able to send two phases down the same multicore, as some places have chosen to use lower-rated insulation on the cable.


Other places have used the more expensive 500V rated cable, which eliminates the restriction.

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But you will find the following paragraph of HSE guidance sheet "Electrical safety for entertainers INDG247" repeated many times as "law":


Three-phase supplies

If lighting is connected to two or three phases of the electrical

supply, use separate dimmer cubicles on different phases to

avoid confusion. Only supply a single phase to any one boom."


To be fair this info sheet is aimed at pub & club performers rather than theatres, but it still gets quoted.

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I think I'm right in saying that this is OK, but if you do it the bars (and anything else involved such as the patch) must have 415V warning labels on them.


I seem to recall that for most standard three phase installs the 415V labels are actually not REQUIRED as a close reading of the regs makes it clear that it is voltage to earth that requires labelling if greater then 240?


Now, I know that everyone puts 415V warning labels on three phase kit, and this is probably a reasonable thing to do, but I don't think it is actually required for compliance with BS7671?

IIRC one of the guidance notes mentions something about this?


Anyone have chapter and verse?



Moderation: This is only re-hashing material that has been covered several times. Please see the latter postings in this thread and several others. Also, the "power" forum is arguably a better place for this discussion. Therefore, this thread is now closed.

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