Understanding Grounding bond bushings better

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mole king

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loveland Colorado U.S.A
I find that the use of the grounding bond bushings where I work is being overused and their purpose is mis understood......or quite possibly I'm wrong in my understanding. I feel that they are only necessary under normal circumstances (not in specs, grounding conductors installed, average commercial application) to be on incoming service to MDP from the utility that is in a metal conduit with no grounding electrode conductor (of course) and coming into a metal enclosure with concentric or eccentric knockouts. Other than that (again no specs or hazardous locations) I feel threaded plastic bushing if your running #4 or larger should suffice. I understand that the N.E.C is the minimum standard but I need to establish a baseline.
Your time and attention and knowledge is of great value
 
mole king said:
I find that the use of the grounding bond bushings where I work is being overused and their purpose is mis understood......or quite possibly I'm wrong in my understanding. I feel that they are only necessary under normal circumstances (not in specs, grounding conductors installed, average commercial application) to be on incoming service to MDP from the utility that is in a metal conduit with no grounding electrode conductor (of course) and coming into a metal enclosure with concentric or eccentric knockouts. Other than that (again no specs or hazardous locations) I feel threaded plastic bushing if your running #4 or larger should suffice. I understand that the N.E.C is the minimum standard but I need to establish a baseline.
Your time and attention and knowledge is of great value
Click to expand...

You can use the NEC as a baseline. That is what it is. I use more grounding bushings than
required. My help tends to only the minimum. I don’t make them add, and they don’t roll their eyes too much when I put on two. As standard practice, we pull an EG in almost everything.

Definite Low bid projects get absolute minimum.
 
Someone find that thread with the flow chart. I think Carultuch made it?

The other major items you are missing are circuits over 250V and plastic enclosures.
 
Bonding of metallic service raceways must always be by something other than a standard locknut.

Majority of other situations where additional bonding methods are required involves missing or impaired continuity in one way or another.
 
Looking at that flow chart: If I have a piece of 3/4" EMT going between 2 4S metal '1900' boxes and there is an ECG pulled in:
Metal raceway = Y
Metal Enclosure with integrated Hubs or female entry = N
GEC inside raceway = Y
Now a bond bushing is required at each end?
Nonsense.
 
tortuga said:
Looking at that flow chart: If I have a piece of 3/4" EMT going between 2 4S metal '1900' boxes and there is an ECG pulled in:
Metal raceway = Y
Metal Enclosure with integrated Hubs or female entry = N
GEC inside raceway = Y
Now a bond bushing is required at each end?
Nonsense.
Click to expand...

You may have read it incorrectly, the chart says GEC bushing required not EGC. Are you referring to the EGC in your example or a GEC.
 
Ahhh thanks yeah read that too quickly ;)
We have run into that with conduits to roof top solar.
 
The thing about rooftop solar arrays is that in some cases it was a GEC and a few AHJs still can't get that out of their head, or have screwy ideas about 250.4.
 
jaggedben said:
Someone find that thread with the flow chart. I think Carultuch made it?

The other major items you are missing are circuits over 250V and plastic enclosures.
Click to expand...

There should be another decision diamond after "properly bonded on other end", to check for whether a wire EGC is used. Obviously, if you use your raceway as an EGC, it needs bonding to the equipment on both ends, either through a bonding bushing, or through standard locknuts getting your continuity in a code-compliant setup.
 
Carultch said:
There should be another decision diamond after "properly bonded on other end", to check for whether a wire EGC is used. Obviously, if you use your raceway as an EGC, it needs bonding to the equipment on both ends, either through a bonding bushing, or through standard locknuts getting your continuity in a code-compliant setup.
Click to expand...
this is for a non metallic enclosure, and the flow chart is for determining if a grounding bushing or other additional bonding method is needed for the raceway/fitting. If bonded properly on other end (or anywhere on that length of run for that matter) no additional bonding is needed for the raceway. That don't mean you won't possibly need either a wire EGC inside the raceway or a bonding bushing to be able to extend the EGC into and/or beyond the non metallic enclosure, but that is not the purpose of the flowchart.
 
Actually there's another problem with the chart. 'Metal raceway' is not specific enough, as FMC, for example, isn't allowed to be used as an EGC.
 
jaggedben said:
Actually there's another problem with the chart. 'Metal raceway' is not specific enough, as FMC, for example, isn't allowed to be used as an EGC.
Click to expand...

I agree with your point but some FMC is permitted as an EGC.

250.118
(5) Listed flexible metal conduit meeting all the following
conditions:
a. The conduit is terminated in listed fittings.
b. The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible
metal conduit in the same ground-fault current path does not exceed 1.8 m (6 ft).
d. If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from
equipment or to provide flexibility for equipment that requires movement after installation, an equipment
grounding conductor shall be installed.
Click to expand...
 
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