Cable Tray

Des 56 · Jan 31, 2009

The consensus here seems to be that cable tray cant be used as a protective conductor
Whilst I agree with most of the points against thats been posted
I would like to refer you to 543.2 Types of protective conductor

Now whilst I have never considered the question before because like some have pointed out, the lack of need for this and the problems that are associated with it make it a no go either way

If you read 543.2.2 vi
A protective conductor may consist of one of the following
Quote
A metal conduit etc etc etc or electrically continuous support system
Now I think a tray can be defined in this way and therefore as long as it is continuous there it seems to fit the bill as a protective conductor but probably not as a circuit protective conductor

As an aside to this comment My understanding was that in the 16th edition bonding of a tray was not necessary unless it exited/entered a building
Does the 17th advise on this

desertbootz · Feb 2, 2009

I've come across a ton of rusty galv and even stainless. Maybe your installations aren't supposed to last like mine are :O) Oooh that was harsh and only kidding but seriously, maybe I should've put a question mark after the rust statement?

Electrically continuous surely means you have a very high degree of certainty that it will stay that way (at least between inspection periods). I would question whether you can have complete confidence in the connection between one piece of tray and another when they've been designed for mechanical rather than electrical integrity. Maybe it's a marine thing? I wouldn't trust stainless not to rust let alone galv but then I'm always learning, specially from you land lubbers

CableTie · Feb 2, 2009

Thank you all for your comments on cable tray as a cpc. Whilst I have never contemplated using it as the cpc as I was taught it is a no go area, but must be bonded, I have wondered why it can't be used.

Some comments make reference to the tray being modified at at later date and therefore effecting its continuity. The same argument could be applied to steel conduit. I have had situations where the existing conduit has been modified in order to add additional circuits.

Equally, arguments on joints becoming loose, rusting or corroding and therefore effecting the overal continuity apply equally to steel conduit and trunking systems as it does to tray.

Still waiting for a difinitive reason - if there is one,

CableTie.