Bonding Bushings

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fluvialist

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80301
We have been using bonding bushings on EMT fittings without the fitting locknut. The inspector just told us that we are required to still use the locknut even though the set screw on the bushing doesn't make contact with the fitting threads. Has anyone else run into this issue? When we don't use the locknut we can get the fitting wrench tight and still get teh set screw to make contact with the threads.
Thanks for your help with this one.
 

iwire

Moderator
Staff member
Location
Massachusetts
We have been using bonding bushings on EMT fittings without the fitting locknut. The inspector just told us that we are required to still use the locknut even though the set screw on the bushing doesn't make contact with the fitting threads. Has anyone else run into this issue? When we don't use the locknut we can get the fitting wrench tight and still get teh set screw to make contact with the threads.
Thanks for your help with this one.

The inspector is mistaken.

Here is part of 300.4(G)

Conduit bushings constructed wholly of insulating material shall not be used to secure a fitting or raceway.

This tells us if the bushing is made partly of metal as a bonding bushing is the. NEC allows it.
 

ActionDave

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Location
Durango, CO, 10 h 20 min from the winged horses.
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Licensed Electrician
We have been using bonding bushings on EMT fittings without the fitting locknut. The inspector just told us that we are required to still use the locknut even though the set screw on the bushing doesn't make contact with the fitting threads. Has anyone else run into this issue? When we don't use the locknut we can get the fitting wrench tight and still get teh set screw to make contact with the threads.
Thanks for your help with this one.
Just curious, what is the application?
 

electricalist

Senior Member
Location
dallas tx
When you say emt fitting . Are you saying the same thing as emt connectors that are going into equipment through a hole sized for the connector.
 

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
I would expect that the threads on the EMT connector are too long to permit a bushing to tightly secure the connector to the enclosure. If that is the case, you need to use the locknut.
 

electricalist

Senior Member
Location
dallas tx
I would expect that the threads on the EMT connector are too long to permit a bushing to tightly secure the connector to the enclosure. If that is the case, you need to use the locknut.
Off the top of my head I cant say I recall a connector yhat a bonding bushing would thread enough to secure the connector. I m also as others thinking the op words as if they installed many. I could picture an inspector making them put the lockrings but not inform them if they didnt need the bonding bushing
 

Cletis

Senior Member
Location
OH
I've bee putting these in. They don't thread at all, just clamp. I call them the Oopsy Bonding Bushing. You know, when someone forgets to put it on during initial installation.
 

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edlee

Senior Member
We have been using bonding bushings on EMT fittings without the fitting locknut. The inspector just told us that we are required to still use the locknut even though the set screw on the bushing doesn't make contact with the fitting threads. Has anyone else run into this issue? When we don't use the locknut we can get the fitting wrench tight and still get teh set screw to make contact with the threads.
Thanks for your help with this one.

I've never had a problem getting the BB set-screw to connect when there is a locknut. And I've never seen a BB that screws all the way down and mechanically tightens an EMT connector without a locknut.

I always put on a locknut.

That said, it's pretty obvious that the point of the locknut is to mechanically tighten the connector against the sheet metal of the box or can and hold it securely in place. If your bonding bushings do that then I might take issue with your inspector's opinion.

...........Ed
 
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kwired

Electron manager
Location
NE Nebraska
Not all fittings have same length of threads, I have seen some that don't leave enough thread to secure a bushing if a locknut is installed first. Box wall thickness can make a difference here as well.
 

IBEW73

Member
Location
United States
bonding bushings

bonding bushings

I have a question?? Debate in our camp over use of bonding bushing. 60 A/480 V Nema 3R Disconnect, 1" Rigid to can, locknut outside of can, lock nut inside, RTU, no gaskets used to seal connection from weather, concentric knockouts , is the set screw on the bonding bushing mandatory if bushing is tight to conduit and lock nut. I can not find in ART.300 NEC were it says set screw is has to be used.
 

GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I have a question?? Debate in our camp over use of bonding bushing. 60 A/480 V Nema 3R Disconnect, 1" Rigid to can, locknut outside of can, lock nut inside, RTU, no gaskets used to seal connection from weather, concentric knockouts , is the set screw on the bonding bushing mandatory if bushing is tight to conduit and lock nut. I can not find in ART.300 NEC were it says set screw is has to be used.
If the manufacturer's instructions tell you to tighten the screw, that determines the conditions under which the part was tested for listing.
I doubt that the instructions set out specific conditions under which you do not need the screw, and it would be hard to impossible for the inspector to verify it if they did.
 

kwired

Electron manager
Location
NE Nebraska
I have a question?? Debate in our camp over use of bonding bushing. 60 A/480 V Nema 3R Disconnect, 1" Rigid to can, locknut outside of can, lock nut inside, RTU, no gaskets used to seal connection from weather, concentric knockouts , is the set screw on the bonding bushing mandatory if bushing is tight to conduit and lock nut. I can not find in ART.300 NEC were it says set screw is has to be used.
The NEC section you are looking for is not in chapter 3 it is in 110.3(B). Very likely the listing says you must use that set screw, as it's primary function is most likely to ensure there is a positive bond to the raceway or fitting it is attached to.
 
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