# Grounding Parallel Tray Cables



## John (Jan 22, 2007)

Reseman said:


> We ran two separate runs of 3C/350 w Ground in a cable tray to the same 480v panel. The run was around three hundred feet.
> 
> The city inspector rejected this because he said that the grounding conductor in the tray cable is now too small. He says it should be sized to both of parallel 350 cables combined.
> 
> ...


You need to ask him to tell YOU what part of the code or local ordnance he is referencing. 

….it’s equivalent to a cop stopping you and handing you a blank ticket. :no:


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## leland (Dec 28, 2007)

Agreed. Red Tag, It is the AHJs' Job to Tell You, What the violation is. Art. etc.
Not to Quiz you on the code.


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## RePhase277 (Feb 5, 2008)

Check out 392.7 It basically states that the cable tray can be used as a grounding conductor if the cross sectional area of both side rails is sufficient to meet the specifications in Table 392.7(B). The cross sectional area should be stamped or marked on the tray sections. It is sized by the overcurrent device protecting the circuit.

I think you may be able to avoid replacing the tray by simply running an equipment grounding conductor of the appropriate size and bonding it to each tray section.


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## leland (Dec 28, 2007)

Bonding the tray should go without saying. But we all missed that part.
Thanx for stateing it.


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## RePhase277 (Feb 5, 2008)

Holy snikies! I just re-read it and realized you weren't talking about the cable tray as an EGC. But you are asking about the EGC in the cable itself. Well, what size is the EGC? He may be right. Take a look at 250.122(F).

But if the service has GFPE, you may be saved by 250.122(F)(2)

Hope this helps.


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## Reseman (Dec 27, 2007)

*Yeah*



InPhase277 said:


> Holy snikies! I just re-read it and realized you weren't talking about the cable tray as an EGC. But you are asking about the EGC in the cable itself. Well, what size is the EGC? He may be right. Take a look at 250.122(F).
> 
> But if the service has GFPE, you may be saved by 250.122(F)(2)
> 
> Hope this helps.


I think its a 600 amp panel. It shows a AWG #1 for the EGC. The EGC inside the cables won't be sufficient. The inspector says there needs to be a #1 installed inside of the tray cable. 

Is there anything in the NEC stating that the inspector is wrong?


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## RePhase277 (Feb 5, 2008)

Reseman said:


> I think its a 600 amp panel. It shows a AWG #1 for the EGC. The EGC inside the cables won't be sufficient. The inspector says there needs to be a #1 installed inside of the tray cable.
> 
> Is there anything in the NEC stating that the inspector is wrong?


I don't think so. I think he is right on this one. I don't think I would fail you for it, but he's not wrong either. Check into the questions below.

The cable tray itself is an EGC. But it is sized according to the overcurrent protection of the largest circuit. What size breaker feeds your parallel set? If your service is ground fault protected, then the EGC can be sized according to the trip setting of the GFPE. If you have GFPE, and the trip setting is less than the ampacity of the EGC in one cable, then 250.122(F)(2) would allow your install.

Otherwise, I think you got a pretty sharp inspector there, and he may be able to be sweet talked if you another EGC in the tray, and bond it at every section and at the equipment at both ends.


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## nap (Dec 26, 2007)

I agree with 277 on this one other than I don;t know about bonding the conductor on every section of tray. I don't see why it would not be acceptable to simply use bonding jumpers, or maybe not even that if the connectors used are rated for the purpose of bonding.


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## RePhase277 (Feb 5, 2008)

nap said:


> I agree with 277 on this one other than I don;t know about bonding the conductor on every section of tray. I don't see why it would not be acceptable to simply use bonding jumpers, or maybe not even that if the connectors used are rated for the purpose of bonding.


I only say bond every section because i will make the inspector feel that this is an over the top install, in addition to the tray connectors. But I never did like the idea of the tray being the sole EGC anyhow.


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## Reseman (Dec 27, 2007)

*Oh, by the way*



InPhase277 said:


> I only say bond every section because i will make the inspector feel that this is an over the top install, in addition to the tray connectors. But I never did like the idea of the tray being the sole EGC anyhow.



The 36" tray has 4/0 bare grounding conductor connected to the tray all the way from the panel to the switchgear. It stops right before the panel.


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## martinkulik (Jan 9, 2009)

*Derating*

Hi did you use the derating rule for both conductors? Use table 310.20 on page 70-152 of NEC code. Most of the info is in article 310.00
Martin

We ran two separate runs of 3C/350 w Ground in a cable tray to the same 480v panel. The run was around three hundred feet.

The city inspector rejected this because he said that the grounding conductor in the tray cable is now too small. He says it should be sized to both of parallel 350 cables combined. 

Has anyone heard of this? I want to know if he is correct? and if he isn't, what articles support that he is incorrect? 



Please help......cuz we may have to pull out both tray cables.....and you know how much that would suck!!!!![/quote]


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