EGC from 2 separate systems...same box

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Ok, I'm having an argument with a fellow at work. Right now we have 2 circuits from 2 separate systems being spliced in the same metal box. One of the circuits is 110v being fed from a 3 phase 208 system, and the other is a 110v circuit being fed from an optional standby system. My contention is that because both systems are being spliced within the metal box, they both need to be bonded to the box. Therefore I said that having one pigtail coming off of the ground screw, and then splicing all the EGC's together would suffice.

HIS contention is that no, because they are 2 separate systems the EGCs should remain separate. We both spent time scouring through the code and neither of us could find a definite answer one way or the other. It makes sense to me that because all the EGC is doing is maintaining the same potential between raceways, enclosures, etc. and providing a path to ground in case of a fault, that there would be no adverse effects from splicing them all together. The only code I could find to solidify my argument is 250.148. If they both have to be bonded to the box, then it doesn't matter if it is 2 separate ground screws or if they're both under the same wire nut. They're going to be connected regardless.

I would really appreciate some opinions, and preferrably opinions with code sections. Thanks in advance
 

augie47

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Likewise. Your EGC will, at some point, be connected to your grounding electrodes and your grounding electrodes for both systems should be common or connected so the EGC are already tied.
 

bshabit

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Can you tell me if it is permissable and correct to install an egc from the ground bar in the stand by panel directly to the ground bar in a normal power panel
 

bshabit

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can you please tell me if it is permissable and correct to install an egc from the stand by panel ground bar to the ground bar of a normal power panel
 

roger

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Can you tell me if it is permissable and correct to install an egc from the ground bar in the stand by panel directly to the ground bar in a normal power panel

Yes it's permissible and correct. Article 517.14 even requires it for different systems feeding a patient care area.

Roger
 

bshabit

Member
one more question if you have a 480v circuit and a 120v circuit in the same junction box wouldn't you keep the egc's separate because they come from separate panels? Now I understand that all the egc's are bonded to the steel but my belief was they were only supposed to be tied together at the source.
 

roger

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one more question if you have a 480v circuit and a 120v circuit in the same junction box wouldn't you keep the egc's separate because they come from separate panels? Now I understand that all the egc's are bonded to the steel but my belief was they were only supposed to be tied together at the source.

Nope, it doesn't matter where they are joined or how many times.

Roger
 

djd

Senior Member
djd

djd

This is a very good question, it reminds me during my apprentice ship the contractor hab us use an isolated ground bar and a no. 6 ground to a ground rod whether tha was local code or not im not sure, I thought was the way, reading the code does clarify. That was in the early 80"s.
 

hurk27

Senior Member
one more question if you have a 480v circuit and a 120v circuit in the same junction box wouldn't you keep the egc's separate because they come from separate panels? Now I understand that all the egc's are bonded to the steel but my belief was they were only supposed to be tied together at the source.

Now your confusing EGC's and neutral (grounded conductor) requirements

EGCs are allow and in fact many times required to be all connected together, this reason is one of the reasons behind the requirement to make sure the X/0 on the secondary is bonded back to the supply system so there is a fault path for the secondary to both systems, since EGCs do not carry normal load current like the grounded conductor, these multiple connections pose no hazard.
And the fact many of us still just use the conduit as the EGC allowed in 250.118 which will all be interconnected one way or another.
 
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