SIGH i need clear explanation of these grounding and bonding terms please

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davidbananas999

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So I am taking my journeymens test in 6 days! I can not for the life of me get these terms straight in my head. I feel like they're all the same things, but each has a different name depending on where it's installed.
One thing I do understand is the service neutral and whatever grounding thingy can only be connected (bonded?) in 1 spot otherwise you can get objectional currents on wires running in parallel. Or something like that.

PLEASE clearly explain each of these terms, and provide a straight-forward example of where each is used:


  • equipment grounding conductor
  • grounding electrode conductor
  • system bonding jumper
  • supply side bonding jumper
  • main bonding jumper

Bonus questions:

Where are bonding bushings required?

What are the benefits or requirements for installing the grounding thingy outside of FMC?

Do I need to connect the grounding terminal for switches, receptacles, or gfci receptacles to a surface-mounted 4-square box, using a raised exposed work cover,
if the box is installed with EMT all the way back to the panel?

THANK YOU SO MUCH!
 
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davidbananas999 said:
  • equipment grounding conductor
  • grounding electrode conductor
  • system bonding jumper
  • supply side bonding jumper
  • main bonding jumper
Click to expand...
I will take a stab at it.

EGC connects all the conductive pieces such as panels raceways cabinets and not supposed to be normally energized. Conduit is a common EGC.

Gec is a conductor that connects the grounding electrode system to the electrical system or the service. An example would be the wire that runs from a ground rod to the neutral bar of a panel board at a service

SBJ is a bonding conductor that connects the electrical system to the EGC. A common example is the screw that goes through the neutral bar of a panel board and into the sheet metal of the panel board enclosure.

SSBJ is a bonding conductor that goes with unprotected service wires such as from the first point of disconnection back to the meter.

SBJ it's basically the same thing as an mbj except it is used in a system instead of a service
 
Thanks bob! Anyone else who wants to add specific examples would be much appreciated. Keep in mind I mostly do commercial and residential.

Also where does the ground go to from a SDS?

Im sorry i have so many questions about this.

Ps i see now there is a forum just for grounding vs bonding so if a mod wants to move this thread feel free.

Thanks you masters!
 
I think your best bet is to read through Article 250 of the NEC Handbook to better understand these terms and where they are used. There are also lots of exhibits that show examples of each.
 
I never understood how the green screw in a panel could be called an SBJ. It doesn't bond the neutral to the ground, that's already done in a service panel as both bars are connected permanently at the factory. All the screw does is bond the metal of the case to the 'floating' neutral/ground bar.
 
K8MHZ said:
I never understood how the green screw in a panel could be called an SBJ. It doesn't bond the neutral to the ground, that's already done in a service panel as both bars are connected permanently at the factory. All the screw does is bond the metal of the case to the 'floating' neutral/ground bar.
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That would only apply to equipment that is listed and marked "suitable only for use as service equipment". These panels will not have a factory supplied green screw or other type of field installed MBJ.
In my experience most service equipment is listed and marked "suitable for use as service equipment". Panels marked like this will have a factory supplied, field installed MBJ.
 
don_resqcapt19 said:
That would only apply to equipment that is listed and marked "suitable only for use as service equipment". These panels will not have a factory supplied green screw or other type of field installed MBJ.
In my experience most service equipment is listed and marked "suitable for use as service equipment". Panels marked like this will have a factory supplied, field installed MBJ.
Click to expand...

In any event, the purpose of the green screw is to connect the metal enclosure to the grounding system, not to bond the grounded conductor to the grounding conductor, correct?
 
K8MHZ said:
In any event, the purpose of the green screw is to connect the metal enclosure to the grounding system, not to bond the grounded conductor to the grounding conductor, correct?
Click to expand...
Not correct.
Bonding Jumper, Main. The connection between the grounded circuit conductor and the equipment grounding conductor at the service.
Click to expand...
The green screw is the main bonding jumper.
 
don_resqcapt19 said:
Not correct.

The green screw is the main bonding jumper.
Click to expand...

But, the green screw is not connecting two conductors together, it's connecting an enclosure to a conductor.

In a panel with two buss bars, not electrically connected, is a screw permitted to be a main bonding jumper?

Article 250 states the main bonding jumper be sized, and not be smaller than the required GEC in Table 250.66

I don't see a column for steel screws, hence my confusion. Also, I wouldn't trust 3 threads of a #10 steel screw in a steel sheet metal box to be adequate to carry enough fault current back to the breaker in the event of a fault.
 
K8MHZ said:
But, the green screw is not connecting two conductors together, it's connecting an enclosure to a conductor.
Click to expand...
And the EGC terminal bus is the enclosure... or an EGC terminal bus is connected to the enclosure. We cannot field fabricate that same main bonding jumper method, but we can field install any manufacturer listed accessory.


In a panel with two buss bars, not electrically connected, is a screw permitted to be a main bonding jumper?
Click to expand...
Permitted where panelboard is listed SUSE and screw is supplied by the manufacturer of the panelboard [250.8(A)(7)].


Article 250 states the main bonding jumper be sized, and not be smaller than the required GEC in Table 250.66


I don't see a column for steel screws, hence my confusion. Also, I wouldn't trust 3 threads of a #10 steel screw in a steel sheet metal box to be adequate to carry enough fault current back to the breaker in the event of a fault.
Click to expand...
Actually, MBJ gets sized to Table 250.102(C)(1). Obviously, that only applies to wire-type jumpers... while Code specifies a jumper must be a wire, bus, screw, or similar suitable conductor. :happyyes:
 
K8MHZ said:
250.8 is only for the connection of the jumpers, not the jumpers themselves.
Click to expand...
250.28(A) permits the main bonding jumper to be a screw. There is nothing in the code about the sizing of the screw used as a main bonding jumper. If I was inspecting, I would accept the screw that was provided with the panel for this application. I would not permit a field selected screw.
 
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