cable size for lights

Postby drm » Thu Oct 30, 2008 9:42 pm

Hi, if using 1.5mm to rewire the lighting circuit in a 2 bed terrace, can 1.0mm cable be used for all the switches ( can only find 1.0mm 2-way 3 core + E cable) or should we just use 1.0mm throughout? Cheers!
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Joined: Thu Oct 30, 2008 9:30 pm


Simply Build It

Postby ericmark » Fri Oct 31, 2008 1:06 am

My son and I were talking about the same thing a couple of days ago. It does state that where cable changes in size there should be a over current device 433.2.1 Except where Regulation 433.2.2 or 433.3 applies, a device for protection against overload shall be installed at the point where a reduction occurs in the value of the current-carrying capacity of the conductors of the installation.
This seems to say we can’t change size but 433.3.1 General A device for protection against overload need not be provided:
(i) for a conductor situated on the load side of the point where a reduction occurs in the value of current-carrying capacity, where the conductor is effectively protected against overload by a protective device installed on the supply side of that point.
Now this seems to me to change everything and starts to make sense, one of the main points is ceiling roses are only rated at 5 amp and the flex from every ceiling rose could be as low as 0.75mm² which is also rated at only 6 amp so even though lighting can use up to 16 amp because of the ceiling rose we all limited to 6 amp so at 1mm² rated around 13 amp there can be no real problem in swapping between 1 and 1.5mm² at least this was the conclusion my son and I came up with.
I know I could have just said yes you can use it but I am sure someone will then say I was wrong so I am giving reasons.

Postby drm » Mon Nov 03, 2008 10:59 am

That's how i thought it was, too. However, i think i'll play it safe and just use 1.0mm throughout. Cheers Eric!
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Joined: Thu Oct 30, 2008 9:30 pm

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