Adding ground bars

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John Wayne

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Hello all - I looked at a panel box the other day and there were multiple neutrals under one screw. The box has two holes on each side for ground bars. If I add a bar on each side to Relocate ground wires do I need to connect them to the neutral bar? The biggest ground is a number six stranded. Thanks
 
No, the EGC bus can terminate directly on the enclosure. The bus and screw combination are listed to provide an adequate path for the fault current.
 
If those holes were intended for the installation of grounding bars it is good to go. If they were not intended for that purpose, the thickness of the panel enclosure is probably not enough to engage two threads of the mounting screw. If you can't engage at least two threads, you will have to use a nut on the back side.
 
infinity said:
No, the EGC bus can terminate directly on the enclosure. The bus and screw combination are listed to provide an adequate path for the fault current.
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Not to pick a fight, but I believe he's asking if he installs a separate ground bar, does he need to connect this new EGC (equipment grounding conductor) bus bar to the neutral bus / grounded conductor... and the answer would be YES (if he's at his first point of disconnect) via the MBJ (main bonding jumper)... and the main bonding jumper is only allowed to be (1) a wire or (2) a bus bar. I don't see an allowance for using the panel enclosure as a means of bonding the EGC bus bar to the neutral bus bar? Would that not be considered objectionable current?

I'm just asking because I always install a wire type MBJ from the EGC bus bar to the neutral bus at the first point of disconnect.
 
don_resqcapt19 said:
If those holes were intended for the installation of grounding bars it is good to go. If they were not intended for that purpose, the thickness of the panel enclosure is probably not enough to engage two threads of the mounting screw. If you can't engage at least two threads, you will have to use a nut on the back side.
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Would using a nut be an acceptable means of bonding if you don't have the two threads engaged? I thought the engagement of two threads was required and there was no way around it...
 
Jerramundi said:
Not to pick a fight, but I believe he's asking if he installs a separate ground bar, does he need to connect this new EGC (equipment grounding conductor) bus bar to the neutral bus / grounded conductor... and the answer would be YES (if he's at his first point of disconnect) via the MBJ (main bonding jumper)... and the main bonding jumper is only allowed to be (1) a wire or (2) a bus bar. I don't see an allowance for using the panel enclosure as a means of bonding the EGC bus bar to the neutral bus bar? Would that not be considered objectionable current?
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The metal enclosure is a suitable path back to the neutral through the MBJ, a separate jumper is not required.
 
infinity said:
The metal enclosure is a suitable path back to the neutral through the MBJ, a separate jumper is not required.
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Not that I doubt you, but is there anything that backs this up? I read 250 as saying the MBJ can be only a bus bar or wire type jumper, meaning the terminal bar itself can serve as the MBJ or you have to use a wire. What allows us to use the enclosure? Is it in the panel listing? Am I missing something in 250?
 
Jerramundi said:
Not that I doubt you, but is there anything that backs this up? I read 250 as saying the MBJ can be only a bus bar or wire type jumper, meaning the terminal bar itself can serve as the MBJ or you have to use a wire. What allows us to use the enclosure? Is it in the panel listing? Am I missing something in 250?
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What you're missing is that the screws that connect the EGC bus to the panel are not the MBJ. The MBJ connects the neutral to the enclosure.

Bonding Jumper, Main. The connection between the grounded circuit conductor and the equipment grounding conductor at the service.
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infinity said:
What you're missing is that the screws that connect the EGC bus to the panel are not the MBJ. The MBJ connects the neutral to the enclosure.
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I'm not saying the screws used to mount the EGC bus are the MBJ. I'm wondering whether or not the panel enclosure itself could serve as the MBJ... because in the instance that there is no wire-type jumper between the separate EGC bus bar and the neutral bus... the panel enclosure would be the ground fault current path between the EGC's and the system neutral.

I'll admit I'm no master, but this to me sounds like objectionable current.

And then there's 250.24(B) which explicitly requires an "unspliced" MBJ used to connect:
(1) the equipment grounding conductor(s) and (2) the service-disconnect enclosure to the (3) grounded conductor...

The use of the word "unspliced" to me says wire... no?
 
It's no different than any conduit system without a wire EGC. Note that the electrode conductors should land on the neutral bus, not the EGC bus, so the enclosure is not part of the service bonding system.
 
LarryFine said:
It's no different than any conduit system without a wire EGC. Note that the electrode conductors should land on the neutral bus, not the EGC bus, so the enclosure is not part of the service bonding system.
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Well the GEC can land on the EGC bus bar if there is a wire-type jumper to the neutral bus, yes?
 
Jerramundi said:
I'm not saying the screws used to mount the EGC bus are the MBJ. I'm wondering whether or not the panel enclosure itself could serve as the MBJ... because in the instance that there is no wire-type jumper between the separate EGC bus bar and the neutral bus... the panel enclosure would be the ground fault current path between the EGC's and the system neutral.

I'll admit I'm no master, but this to me sounds like objectionable current.

And then there's 250.24(B) which explicitly requires an "unspliced" MBJ used to connect:
(1) the equipment grounding conductor(s) and (2) the service-disconnect enclosure to the (3) grounded conductor...

The use of the word "unspliced" to me says wire... no?
Click to expand...
Objectionable current is current that flows under normal conditions not in a fault condition so that has nothing to do with it. If all of the branch circuits were in MC-ap or AC cable you wouldn't need an EGC bus because there would be no wire type EGC's. The cable sheath (EGC) connected to the panel enclosure is all that's required.
 
infinity said:
Objectionable current is current that flows under normal conditions not in a fault condition so that has nothing to do with it. If all of the branch circuits were in MC-ap or AC cable you wouldn't need an EGC bus because there would be no wire type EGC's. The cable sheath (EGC) connected to the panel enclosure is all that's required.
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Fair points.. and you're correct. I was mistaken about the definition of Objectionable Current.
But what about 250.24(B)'s explicit use of the word "unspliced?"
 
@Jerramundi
How do you think an EGC bar is usually attached to a panel? It is attached by screws. Even though the screws are not the MBJ, some panels use a screw through the neutral bus into the panel for a MBJ.
You keep mentioning objectable current, an EGC is not for carrying current unless it's carrying fault current to activate a OCPD. There is no normal current carried through the EGC. What you can't do is use the panel enclosure to carry neutral current.
 
infinity said:
The metal enclosure is a suitable path back to the neutral through the MBJ, a separate jumper is not required.
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You are correct Picture this
91JMcCvB0wL._AC_SY450_.jpg
Notice green screw on neutral bus? That makes connection between grounding terminals and neutral through the enclosure (MBJ) on this panel. If the panel you have doesn't have this optional screw, then a jumper would be needed (if required) between ground lug and neutral, but the ground bars installed correctly wouldn't need any additional bonding between each bar as pictured.
 
Fred B said:
You are correct Picture this
View attachment 2553606
Notice green screw on neutral bus? That makes connection between grounding terminals and neutral through the enclosure (MBJ) on this panel. If the panel you have doesn't have this optional screw, then a jumper would be needed (if required) between ground lug and neutral, but the ground bars installed correctly wouldn't need any additional bonding between each bar as pictured.
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Since this panel does not have a main breaker, is there a situation in which the MBJ screw would be used in this type of panel?
 
Greg1707 said:
Since this panel does not have a main breaker, is there a situation in which the MBJ screw would be used in this type of panel?
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It does have a main CB but if it did not then the MBJ (bonding screw) would not be used for bonding the neutral.
 
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