In article , Mortimer
writes

You mean that two of the phases are the *same* colour?

Yes.

Surely not

Unbelievable but true. Foisted on us by the Eurocrats in Brussels.

: how do
you know whether it's safe to connect two wires if they could be on
different phases?

you don't

And if you connect brown, black and black to a three phase
motor and get the two blacks the wrong way round it will run backwards.

precisely.

I can see the benefit in changing from red+black to brown+blue in T&E as
those are the same colours used in flex, but to go from our previous
widely understood red/yellow/blue + black to the new scheme is less
convincing.

The idea, I think, was to continue the concept that the brown wire is
phase and blue neutral for consistency, but to use two black wires for
the second and third phases... words fail me.

See this:

http://jasper.org.uk/ingleses.jpg

this was an installation where a distribution board built in Britain was
shipped to a remote location in Europe. The Spanish electricians needed
a crib sheet to match up the colours correctly :-)

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