Class II

[timhoward]

Other than when it forms an earthed sheath around the live conductors, how does a CPC protect a cable?

I accept I didn't word it well, but my meaning was it provides a reliable return current path for edge cases when strange things have happened upstream.

The (obscure) old example coming to mind was when a fuse was removed for the lighting circuit (by customer), the lighting circuit cable was cut, and BANG the main fuse blows. It turned out the CU was wired reverse polarity. If that circuit hadn't had a cpc the customer may have found out about the reversed polarity a much nastier way. Granted, that one is not going to happen every day.

 

[Flanders]

So what is the reason for a cpc in final circuit that is supplying a class 2 fitting in a commercial environment.Is this a regulation requirement. I agree it's required in a domestic environment as a class 2 light could be easily changed with a class 1 fitting by the home owner .

 

[telectrix]

it's there so hopefully a nail or screw penetrating the cable will short L-E and thus result in the OCPD tripping out and killing the circuit. ( apart from a L-E short at a classI fitting).