Metal trunking as a cpc

[Sparklms]

Me and a workmatefinished testing a warehouse yesterday which has approx 200 highbay fittings fixed to a metal trunking,the whole lighting installation used the metal trunking as an earth.

Basically my gaffers phoned me today and carried on at me saying the building should be shut down blah blah because of the lightings earthing ,now ive just looked up 543.2.2 in the regs and it clearly states (with conditions) that metal trunking can be used as an adaquate cpc

543.2.2 (vi)

A metal conduit, metallic cable management,
or other enclosure or electrically continuous
support system for conductors

I just wanted to know if hes just carrying on to be a dick or am i right?

In 2008 at my old firm we tested a huge factory in leeds with the same thing ( a building which we had done various installs on) my old gaffer brought the nic man to that job and he had no quams with it so why does my current employer..[/quote][/i][/b]

 

[holmslaw]

..

 

[Risteard]

Of course metallic trunking can be used as the cpc presuming that it is adequate for that purpose. What additional benefit will a small cable provide? The trunking is likely to have a far lower resistance and so the overwhelming majority of the earth fault current will flow through the trunking. Don't forget your flyleads though.

 

[ricicle]

Does the trunking have the correct copper earthing links fitted ?

 

[Adam_151]

You should also inspect joints to containment used as a CPC carefully, especially around switchgear. Its not unusual for dist boards to be changed and the care taken in ensuring good continuity to the containment to be lacking.

You should also inspect the method of earthing fittings to the trunking. Sometimes the bolts holding the fitting to the trunking perform this purpose which if care hasn't been taken to ensure that paint is removed and there is good continuity to other parts of the fitting can give a H/R connection. hopefully there will be a flylead from the fittings earth terminal crimped an lugged onto the trunking inside

 

[holmslaw]

..

 

[bernardgreen]

I recall an incident where trunking used as the CPC was hit by a forklift truck and dislodged from the brackets. The continuity to earth was lost. The cables had enough slack ( and stretch ?) to remain intact so no remedial action was thought necessary.

The immediate effect was that some electronic equipment deprived of the CPC became erratic and it was only from investigating this problem that the loss of effective CPC was discovered.

Use a wire as the main CPC and have the trunking as a backup.