Bonding 3 800mp services in one location

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kjrise

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I was recently at a supermarket that has a single utility transformer feeding 3 800amp panels that are service entrances. The 3 panels are located next to each other.
The installing contractor looped 1 bare continiuos 3/0 ground wire from panel 1 to 2 to 3 then to building steel and down to slab rebar.
He attached the bare wire to a lug bolted to the can of each panel not to the ground bar.
The ground bar and neutral are seperate from this ground lug, he did have a bare neutral jumper but was size at 1 or 1/0.
There was no size of a outdoor ground rod or water pipe grounding.
Question is should all 3 panels be grounded seperately with each one have 1 ground rod, water ground, building steel ground?
If a coomon ground is aceptible does it have to be oversized?
 
Re: Bonding 3 800mp services in one location

I don't see a problem with using the one GEC running to the three panels. I do see some problems with the way the connection has been made at the panel. 250.24 requires the GEC to be connected to the grounded service conductor, not to the enclosure. You mentioned a "bare neutral jumper". If this connects the ground bar to the lug to which the GEC is connected, then it might satisfy 250.24(A)(4), but the jumper would need to be sized in accordance with Table 250.66. If the GEC and the jumper are landed under the same lug, then that would be a problem unless the lug is listed for two conductors.
 
Re: Bonding 3 800mp services in one location

I just got pictures back of this connection. I could e-mail to you, send me a e-mail (deleted e-mail address)

{Please use the private message function for private contacts. We do not permit e-mail addresses in the forum. Thanks.
Don
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[ October 19, 2005, 01:20 PM: Message edited by: don_resqcapt19 ]
 
Re: Bonding 3 800mp services in one location

From what you said 1 to 2 to 3
I would not like that
I would ask you to come out of each panel then make your ground connection outside the panels
 
Re: Bonding 3 800mp services in one location

Originally posted by jimharmon:
I would not like that
I would ask you to come out of each panel then make your ground connection outside the panels
Click to expand...
Based on what code rule?
 
Re: Bonding 3 800mp services in one location

Would this be a good recommendation in this store to install a copper ground bar 1/4" x 3" x 12" with rows of holes for compression fittings & mounted this to insulated standoffs in the electrical room. This will now become your main service grounding point in which separate runs with go out to:
1. Building steel
2. Cold water pipe
3. Re-bar in footing
4. Exterior ground rod in earth
5. Ground bar in MDP-1 800amp
6. Ground bar in MDP-2 800amp
7. Ground bar in REF. Disconnect 1000amp
Additional ground could include telephone equipment ground, satellite / TV source ground and any additional electronic equipment grounds.

In each MDP & disconnect there should be a single ground bar installed. In these panels we observed 3 separate grounding points that where only bonded to the sheet metal cabinets incorrectly & with improper bolts.

Once these ground bars are properly installed the neutral bond needs to be sized per code and run to the neutral bar. The neutral bond jumper that is currently installed is undersized.
 
Re: Bonding 3 800mp services in one location

jimharmon, in my 2002 edition, 250.64(D) reads (IMO) that it is permitted to tap off the GEC to each enclosure. That does not necessarily mean that it is not permitted to have one continuous GEC go from one panel to the next. :)
 
Re: Bonding 3 800mp services in one location

Jim, That section gives me to permission to run taps off of one large GEC. I'm still allowed to loop the GEC through the enclosures if I want.
 
Re: Bonding 3 800mp services in one location

Jim, two issues here:

1) The NEC is a permissive document. If it doesn't say you can't do it, then you can.

2) As an inspector, you can't enforce your own preferences. You have to enforce the NEC as written.
 
Re: Bonding 3 800mp services in one location

kjrise
You did not say what the conductor size is but table 250.66 shows 3/0 as the max size required.
Jim has it correct. The 3/0 should go to the grounding electrode and be bonded to all the other available electrodes as per 250.50. I would have thought you would install 3/0 from each panel grounding bar of the other enclosures and connect the the 3/0 electrode conductor.
He attached the bare wire to a lug bolted to the can of each panel not to the ground bar.
Click to expand...
This sounds as if you are using the sheet metal of the panel as part of the grounding path. Is this proper?
 
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