Help On Using Earth As live?

[6ft2]

Hi Im currently working for a company wiring heating systems up I have had a Job Pulled up By a QS for the company we contract for
Saying it Failed due to Earth conductor being used as a live and seriously dangerous. Ill explain , I had to run a cable in for The Heating time clock and it was a fair run , I needed Live, Neutral, and 3 switch lives ,making 5. I used 1x 5 core flex as I thought that as the timer control was double insulated then I could Sleeve the earth with Brown sleeving and use it as one of the Switch lives. Am I wrong to do this?

 

[Marvo]

Not sure about this one, or you could effectively use the cpc from a T+E as a live (providing the boxes are earthed)

I think the CPC is a smaller sized conductor and not rated to carry constant current.

 

[Ponty Massive]

...but on a lighting cct, using 1.5 the cpc will be 1.0. If this was fused via a 6a mcb, then you could argue this method could be used to get rid of the "borrowed neutral" problem most people have!!

 

[malcolmsanford]

Not sure about this one, or you could effectively use the cpc from a T+E as a live (providing the boxes are earthed)

reg 416.1

 

[Ponty Massive]

haven't got me book with me at the moment malcolm...roughly what does it say??

 

[malcolmsanford]

Live parts shall be completely covered with insulation which can only be removed by destruction

 

[Ponty Massive]

So your saying it's within the regs to use a cpc from a flex cable, sleeve both ends then use that core as a live?

 

[malcolmsanford]

Put it this way ................it is not in the regs that you can not sleeve a Y/G cable in a multi core flex and use it as a LIVE cable.

What is in the reg is

514.4.2
Is that the bi-colour combination of Y/G can only be used as a protective conductor. and

A single core cables that are coloured G/Y alongs it entirely length shall only be used as a protective conductor and can not be over marked at their termination.

So taking them into account, there is nothing in the regs to say you can not in a multi core cable/flex over sleve the G/Y cable .

 

[IQ Electrical]

Malcolm's spot on in that the stipulation of G/Y as a cpc applies only to single-core cables.

Personally, I wouldn't use this method and I doubt if Malcolm would either but in terms of BS7671:2008 it would comply.

 

[Ponty Massive]

I don't think any of us would.....it's an interesting point though.

 

[Ponty Massive]

Live parts shall be completely covered with insulation which can only be removed by destruction

Could this be considered as the outer PVC layer of the T+E ?

 

[IQ Electrical]

Could this be considered as the outer PVC layer of the T+E ?

No, that's sheath as opposed to insulation.

 

[malcolmsanford]

Malcolm's spot on in that the stipulation of G/Y as a cpc applies only to single-core cables.

Personally, I wouldn't use this method and I doubt if Malcolm would either but in terms of BS7671:2008 it would comply.

You are spot on as usual IQ I certainly would not want to do it, and even stopped guys that wanted to use SY cable and the braiding as a protective earth because SY does not conform to any BS stated in reg 522.6.6, though again I would imagine that the sheath is quite capable of doing the job, and perhaps one day the regs will recognise that

 

[Spudnik]

So, in summary, yes, the g/y cpc of a flex can be used as a live conductor provided it is identified as such at either end.

BUT, a single core g/y cable (ie in conduit) CANNOT be used under any circumstances.

Nowt about t&e though.

 

[Deleted member 9648]

I cannot believe anyone would even consider using a conductor intended to be a cpc as a live conductor....even if sleeved at the ends,the dangers are all to obvious. I'm not convinced of your interpretation of 514.4.2.
IMO in order to comply the entire conductor would have to be sleeved over....clearly impossible if the G/Y is contained within a sheath......I disagree with the above, it is not permitted to use a G/Y within a sheathed cable as a live conductor.

 

[truckster]

Not in the BS 7671-2008 Marvo we can use flex as an instalation cable 521.9.3

Hi Malcolm
I hate to find flex used as installation cabling and always thought it was non-compliant but here you have pointed to a reg which says it's ok if 'relevant provisions of the regs are met' Does that simply refer to current carrying capacities etc?