Metal conduit between two light fittings

Ross, very impressed with your memory! :-)

Something tripped a memory about this over the weekend, and following a trip to the archive and going back as far as BS 7671 : 2001 (Amendments 1 & 2) the equivalent regulation to 410.3.9 was 471-13-04.

471-13-04 permitted protective measures against indirect contact to be dispensed with in instances numbered (i) to (vii) one of which was:

'(v) inaccessible lengths of metal conduit not exceeding 150 mm'

If the conduit in the original question has a length ≤ 150 mm and is inaccessible, then it might have complied at one time.

However, the requirement of inaccessibility would be difficult to meet in most situations, as even if the conduit is inaccessible in the normal use of the installation, it is likely to become accessible at some point, for example during maintenance work.

- Ross

AJJewsbury said:

Insulation could be damaged when drawing in

Point taken, but you would have to be pretty ham-fisted to damage the cables in 1 m of conduit.

Hello Mark:

So you were talking about metal Troffers with plastic lens in effectively an outside but covered  area.

As a frame of reference I use troffers in my home ,in work areas (family room, kitchen etc) and changed them over from Fluorescent to LED about 5 years ago.

The LED's are on magnetic stripes and the AC/DC Converter is also mounted on a magnetic strip. This allows one to magnetically attach to the metal in the troffer, without any screws.

The new version of the magnetic LED kit which I recently purchased now allows one to switch lighting intensity and color.

Regarding the carpark -- I hope you are not parking EV cars in the closed area"

Peter Brooks

Palm Bay FL

I struggle to see how a fault could arise within the conduit unless mice could find their way in.

Insulation could be damaged when drawing in (and that likely wouldn't be spotted during an insulation test as the conduit wasn't earthed), or the insulation might be deficient due to a cable manufacturing fault. Even if it was perfect when installed, some problems (e.g. small overloads of long duration) can remain undetected for long enough for insulation to soften and conductors creep to the surface (especially if there are bends or kinks in the conductors) or even genuine faults that don't disconnect as promptly as they should (RCDs stick, wrong fuse rating used or DIY extensions to circuits so loop impedances too high).

A few generations ago we used to put cotton covered rubber singles in unearthed steel conduit - (in a way the cotton braid was seen as a sheath and so the steel was for mechanical protection only) ... but there were sufficient problems, even by the safety standards of yesteryear, for the practice to fall out of favour.

   - Andy.

The works are in a carpark. Swapping fluorescent linear fittings for LED. The discussion was in the office.

Hello Mark:

Just for my education "why" and "what" are you swapping the office lights from - to.

Peter Brooks 

It would be if the conduit wasn't already there. We are simply swapping lights over on an existing installation. The original conduits were not earthed and we connecting fly leads via the lock nuts to the terminal of the fittings. The question was raised in the office weather there was a requirement to do so, but as all here have agreed with the majority of us. It has validated what we are doing. Thanks all!

Hello Chris:

Your question that PVC conduit would be simpler -- is the right answer and cheaper too.

Over here in the US we have flat rectangular PVC conduit 

Peter Brooks

Ross has summed up the Regs very well. Mind you, I struggle to see how a fault could arise within the conduit unless mice could find their way in.

Would PVC conduit not be simpler?