Using CPC as Sw/Live. Acceptable or not?

Nic Norwood · May 30, 2012

Hello all, just a little help required to settle an argument I've been having for the last two days...firstly I'll say that I'm not fully qualified yet...sitting my am2 next week (why I mention this will become clear later).

The other day I was removing some old light fittings and found that a cpc had been sheathed over with red sleeving to identify it as a switch wire, I made a comment that this was not acceptable (as Ive always been told it's not, and believe there's regulations out there that back this up).

Subsequently the 'qualified' spark that I'm working with said to me that because the cable was flex the cpc was double insulated...making this cable class 2. and because of this it was perfectly acceptable as it's only the same as sleeving the neutral as a Sw/Live.

I may have been and may still be wrong here, but I still said it doesn't matter. C.p.c is c.p.c regardless. To which the reply was what do you know you're just an apprentice anyway.

Who's right here, and is there an actual Reg. I can quote to prove my point!?

Deleted member 9648 · May 30, 2012

514.4.2 only prohibits single core G/Y conductors to be overnmarked at terminations...therefore you are incorrect as a sheathed cable with a G/Y conductor can be used as an energised conductor and identified at terminations....(IMHO it should not be permitted).

telectrix · May 30, 2012

but 514.3.2 : note the term preferably throughout it's length. so i consider it bad practice, even if allowed by regs.

Nic Norwood · May 30, 2012

So it come's down to the old chestnut 'good practice vs. bad practice'?

The only reason I argued so much is because the way I saw it the question staring me in the face was...where will the fault current flow if a fault develops in the fitting or the switch...both of which were metal.

telectrix · May 30, 2012

now that's definitely against regs. class 1 fittings with no cpc.

Risteard · May 30, 2012

I always understood it to be prohibited under the 16th Edition, but I'll have to dig out my copy of BS 7671:2001 as amended later on to find the precise wording. As stated above, however, it is permitted except for single-core cables under BS 7671:2008 and as amended.

Nic Norwood · May 30, 2012

Well the switch was class 2 the fitting was class 1. Hence my taking issue with the situation. =\

telectrix · May 30, 2012

even if the switch is class II, the metal back box needs a cpc. don't forget that the faceplate screws are in contact with the box. if a fault was to occur behind the switch, those screws could become live.

LineProducts · May 30, 2012

Nic, regardless of the regs I think that you should be applauded.
Your instinct was to use logic and identify a potentially dangerous situation and then to speak up. Keep it up.

DavidJ91 · Jun 3, 2012

Also, I'd like to know why that spark you were working with was speaking like a complete (insert word here) to you, asking 'what do you know...' . That little detail you found on that CPC could've been the difference between no shock and getting a shock under a fault. Surely seeing as the earth wire is meant to carry fault current away to earth and NOT act as a switch wire, it would be against Regs. I'm just rabbiting on now, Telectrix summed it up earlier lol.

Furthermore, maybe the guy you were working with snapped at you because he installed it all those years ago

I'm a sucker for conspiracy theories :joker:

i=p/u · Jun 3, 2012

metal fittings can still be class 2..

sjm · Jun 3, 2012

telectrix said:
even if the switch is class II, the metal back box needs a cpc. don't forget that the faceplate screws are in contact with the box. if a fault was to occur behind the switch, those screws could become live.

You could use nylon screws.