Bonding

Djelite

Senior Member
Location
Ny
Occupation
Electrician
on service conductors and service equipment a bonding lock nut bonding bushing is required. Is this because these conductors arent protected by a ocpd? Lock nuts are still required for tightening purposes with a bonding bushing, jumper. Is there a bonding bushing, jumper combo where you dont need a regular lock nut?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
If there are no concentric or eccentric KO's you can just use a bonding locknut on one end of the raceway and no bonding bushings would be required. I've only seen bonding bushings that work in conjunction with a locknut for service raceways.
 
. I've only seen bonding bushings that work in conjunction with a locknut for service raceways.

Rob, I had never even considered it, but are you saying you can't use a lock nut on the outside and then a metal bonding bushing on the inside with no lock nut? I thought I remember that being discussed and that we can do it generally but not with service raceways?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Rob, I had never even considered it, but are you saying you can't use a lock nut on the outside and then a metal bonding bushing on the inside with no lock nut? I thought I remember that being discussed and that we can do it generally but not with service raceways?
I don't think that I stated it very clearly, I'm saying that you would need at least one standard locknut and the bonding bushing if you had RMC. An EMT connector would also require a locknut with the bonding bushing.
 

Djelite

Senior Member
Location
Ny
Occupation
Electrician
I don't think that I stated it very clearly, I'm saying that you would need at least one standard locknut and the bonding bushing if you had RMC. An EMT connector would also require a locknut with the bonding bushing.
Good because even the way its worded in the code book might lead people to think a lock nut is nut needed where a bonding bushing/jumper combo is installed. Forther more the fact that they dont explain why atleast in the hand book is disappointing and thats why we have people doing things but dont know why
 

Djelite

Senior Member
Location
Ny
Occupation
Electrician
Good because even the way its worded in the code book might lead people to think a lock nut is nut needed where a bonding bushing/jumper combo is installed. Forther more the fact that they dont explain why atleast in the hand book is disappointing and thats why we have people doing things but dont know why
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
If there are no concentric or eccentric KO's you can just use a bonding locknut on one end of the raceway and no bonding bushings would be required. I've only seen bonding bushings that work in conjunction with a locknut for service raceways.

What about
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I have always had questions on this issue. Here is an explanation from Bridgeport which is actually in the NFPA Link enhanced content


ENHANCED CONTENT
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Standard locknuts, sealing locknuts, and metal bushings are not acceptable as the sole means for bonding a raceway or cable to an enclosure on the line side of the service disconnecting means. For concentric, eccentric, or oversized knockouts, electrical continuity must be ensured through the use of a supply-side bonding jumper that connects the raceway to the enclosure. If these knockouts were in service enclosures, they would impede the bonding connections. Bonding jumpers are required in those situations. They would also be required if reducing washers are used to provide a suitable path for the high level of ground-fault current that is available on the line side of the service disconnecting means.

(1) Bonding equipment to the grounded service conductor in a manner provided in 250.8
The following exhibit illustrates an acceptable grounding and bonding arrangement at a service that has one disconnecting means.
21111052711-70HB20e250-33_edited.jpg
The next exhibit illustrates an acceptable grounding and bonding arrangement for a service that has three disconnecting means as permitted by 230.71(A).
21111052752-70HB20e250-34_edited.jpg
See also 250.24(C), which specifies that the grounded service conductor must be run to each service disconnecting means and be bonded to the disconnecting means enclosure.

(4) Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers
Bonding-type locknuts and grounding and bonding bushings for use with rigid or intermediate metal conduit are provided with means (usually one or more set screws that make positive contact with the conduit) for reliably bonding the bushing and the conduit on which it is threaded to the metal equipment enclosure or box.
Grounding bushings used with fittings for rigid or intermediate metal conduit or with electrical metallic tubing (EMT) have means for connecting a bonding jumper or have means provided by the manufacturer to attach a wire connector. This type of bushing may also have one or more set screws to reliably bond the bushing to the conduit.
Threaded hubs used to connect rigid metal and intermediate metal conduits to service equipment and other line-side enclosures are suitable for bonding the conduit only if they have been listed as grounding and bonding equipment per UL 467, Standard for Grounding and Bonding Equipment. Such hubs are available with gaskets and are suitable for use in wet locations so that a conduit connection can be to an enclosure above the live parts. Grounding and bonding hubs are provided with a grounding and bonding locknut to ensure that the connection between the hub and the conduit is suitable for the higher levels of fault current available at the service location. Although many threaded hubs are listed as conduit fittings, not all threaded hubs have additionally been listed as grounding and bonding equipment. Conduit hubs listed as grounding and bonding equipment are also required (see 250.97) where the conduit contains feeders or branch circuits rated above 250 volts to ground.
The exhibit below shows a listed bonding-type conduit bushing used to connect a threaded conduit to an enclosure and provide the bonding connection required by 250.92(B).
21111052850-70HB20e250-36_edited.jpg
 
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