grounding cable trays

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Take a look at 392.7.

This section does not say anything about grounding cable trays that only support raceways.

Chris
 
raider1 said:
Take a look at 392.7.

This section does not say anything about grounding cable trays that only support raceways.

Chris
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I read 392.7, then posted, then followed 392.7 to 250.96.
392.7 says "(A) Metallic Cable Trays. Metallic cable trays that support electrical conductors shall be grounded as required for conductor enclosures in accordance with 250.96 and Part IV of Article 250."

but 250.96 seems to imply it only needs to be grounded IF it is being uses as an EGC
"250.96 Bonding Other Enclosures.
(A) General. Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non?current-carrying parts that are to serve as grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them. Any nonconductive paint, enamel, or similar coating shall be removed at threads, contact points, and contact surfaces or be connected by means of fittings designed so as to make such removal unnecessary.
(B) Isolated Grounding Circuits. Where installed for the reduction of electrical noise (electromagnetic interference) on the grounding circuit, an equipment enclosure supplied by a branch circuit shall be permitted to be isolated from a raceway containing circuits supplying only that equipment by one or more listed nonmetallic raceway fittings located at the point of attachment of the raceway to the equipment enclosure. The metal raceway shall comply with provisions of this article and shall be supplemented by an internal insulated equipment grounding conductor installed in accordance with 250.146(D) to ground the equipment enclosure."
 
Twoskinsoneman said:
Hey you answer a lot of my questions with short answers and usually give code ref...sweeet.
Thanks
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I try.:)

but 250.96 seems to imply it only needs to be grounded IF it is being uses as an EGC
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The way I read 392.7(A) is that if the cable tray is supporting electrical conductors it must be grounded per 250.96, even if the cable tray is not being used as an equipment grounding conductor.

Chris
 
I say if it is metal, ground it. I have seen some "interesting" situations out there!

In one case all the outlets in an office addition were grounded via the grounds in the wiring connecting to the flourescent light fixtures, which were contacting the suspended ceiling and through one ceiling support cable, which was accidentally screwed into a HVAC duct support, which was grounded by contacting the ductwork (grounded).

The ground for the outlets was not connected at the subpanel which in this case was a fuse box with no ground bar.
 
All noncurrent carrying parts of the electrical system must be grounded.
250.4(A)(2) Grounding of Electrical Equipment Non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.
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don_resqcapt19 said:
All noncurrent carrying parts of the electrical system must be grounded.
Quote:
250.4(A)(2) Grounding of Electrical Equipment Non?current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.
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I don't think a cable tray "encloses" anything... I don't see this ref applies.
 
celtic said:
Just what is 250.120(A) telling us here:-? [in regards to cable tray]
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Seems to tell us IF you are using a cable tray as an equipment grounding conductor, it needs to be installed properly

"250.120 Equipment Grounding Conductor Installation.
An equipment grounding conductor shall be installed in accordance with 250.120(A), (B), and (C).


(A) Raceway, Cable Trays, Cable Armor, Cablebus, or Cable Sheaths. Where it consists of a raceway, cable tray, cable armor, cablebus framework, or cable sheath or where it is a wire within a raceway or cable, it shall be installed in accordance with the applicable provisions in this Code using fittings for joints and terminations approved for use with the type raceway or cable used. All connections, joints, and fittings shall be made tight using suitable tools."

The bold IT refers to the EGC. Where IT is a cable tray it yada yada...
 
Twoskinsoneman said:
I don't think a cable tray "encloses" anything... I don't see this ref applies.
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The cable tray is electrical equipment and is required to be grounded by the section that I quoted.
 
don_resqcapt19 said:
The cable tray is electrical equipment and is required to be grounded by the section that I quoted.
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All you've done is repeat yourself. Will you respond to my claim that the equipment in question has to be "enclosing" electrical conductors?
 
Twoskinsoneman said:
All you've done is repeat yourself. Will you respond to my claim that the equipment in question has to be "enclosing" electrical conductors?
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I don't read it that way, and if you don't like that section I will tell you that in my opinion (AHJ) that the tray without grounding is likely to become energized and cite 250.4(A)(4) to require that the tray be bonded to provide an effective fault clearing path.
 
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don_resqcapt19 said:
I don't read it that way, and if you don't like that section I will tell you that in my opinion (AHJ) that the tray without grounding is likely to become energized and cite 250.4(A)(4) to require that the tray be bonded to provide an effective fault clearing path.
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You certainly could call it "likely to become energized" and I don't think anyone would take the time to argue it even if they disagree.

What do you think the code means when it says "materials enclosing electrical conductors"?

That is what I'd like a discussion about... from anyone who has an opinion.
 
Twoskinsoneman said:
I don't think a cable tray "encloses" anything... I don't see this ref applies.
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I disagree, here is the definition of "enclosed" from Websters on-line dictionary:

1 a (1): to close in : surround <enclose a porch with glass> (2): to fence off (common land) for individual use b: to hold in : confine

I definitely feel that cable tray "holds in" or confines electrical conductors, so my feeling is that cable tray encloses electrical conductors and 250.4(A)(2) would apply.

JMHO,

Chris
 
raider1 said:
I disagree, here is the definition of "enclosed" from Websters on-line dictionary:

1 a (1): to close in : surround <enclose a porch with glass> (2): to fence off (common land) for individual use b: to hold in : confine

I definitely feel that cable tray "holds in" or confines electrical conductors, so my feeling is that cable tray encloses electrical conductors and 250.4(A)(2) would apply.

JMHO,

Chris
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Nice. I agree it seems like a cable tray should always be grounded for just-in-casees. But to hold in? Ha that seems like a stretch. I guess a cable tray should fall under the classification of an enclosure. Since it encloses.

I would not consider a frying pan to be enclosing the egg on it...

Thanks for giving your opinion. I don't think I agree with it but it is nice to hear a couple of other peoples. :smile:
 
Twoskinsoneman said:
But to hold in? Ha that seems like a stretch.
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If the cable tray suddenly was removed what would happen to the conductors?

Would they remain where they where or would they fall?

IMO per Chris's definition the cable tray encloses the conductors

I would not consider a frying pan to be enclosing the egg on it...
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I would not have said so either until I read the definition Chris provided.
 
iwire said:
If the cable tray suddenly was removed what would happen to the conductors?

Would they remain where they where or would they fall?

IMO per Chris's definition the cable tray encloses the conductors



I would not have said so either until I read the definition Chris provided.
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Not to mention that some of the cable trays have covers, so they do indeed 'enclose' the conductors.

The logic of the argument that it is only required to be grounded is also faulty for other reasons. Single conductor cables are allowed to be installed in cable trays? Correct? The insulating properties of the conductor is the same as the one installed in counduit, so if one recognizes that the conduit is 'likley to become energized' what difference exist in the cable tray installation that would eliminate that 'likely'-ness?

(I am somewhat astonished that this is even a question. Do I give people more credit than they deserve? ):D
 
I think that much of the confusion which arises from the NEC is a direct result of the (unfortunate) choice of the words "likely to become energized". This, of course, is hindsight but it would probably be a good thing if some other words could be chosen which reflect what would seem to be the intent of these words. Another choice might be "would have more than a snowball's chance in hell of becoming energized". However, I believe the intent to anyone who has gotten hit by energized ceiling grid, conduit, machinery, enclosures, ducts, metal cable sheaths, plumbing pipe, or numerous other items which, prior to getting a good jolt, would have seemed to not be "likely to become energized".
 
weressl said:
Not to mention that some of the cable trays have covers, so they do indeed 'enclose' the conductors.

The logic of the argument that it is only required to be grounded is also faulty for other reasons. Single conductor cables are allowed to be installed in cable trays? Correct? The insulating properties of the conductor is the same as the one installed in counduit, so if one recognizes that the conduit is 'likley to become energized' what difference exist in the cable tray installation that would eliminate that 'likely'-ness?

(I am somewhat astonished that this is even a question. Do I give people more credit than they deserve? ):D
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You may :grin: .
Although I have said I would ground the tray anyway.
It's just an excercise in picking a single word in the Book to death :smile: .
I'm doing battle within right now on the damned "to hold" part of the definition of "enclose" I see in EVERY dictionary and the fact that I don't believe that the NEC meant "to hold" based on my own preconceived notion of what enclosed means. Also I'm having a hard time being persuaded by your arguements based on the fact that I think your biased toward grounding everything (which is a good bias), and not being honest about your preconceived notion of the word "enclosed".

You may be right that the definition may include "to hold", but do you believe this is the intended definition... althouth intented doesn't really matter.

Hold your hand out and grab the bottom of a glass of beer... no one thinks "I'm enclosing this beer."
 
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