Another bond bushing question

nickelec

Senior Member
Location
US
Here's my scenario all metallic equipment less then 250v the way I understand is no bonding bushings are required on any of this equipment that is on the LOAD side of service switch , weather concentric or non-consentric Kos.does anyone disagree?

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infinity

Moderator
Staff member
Location
New Jersey
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Journeyman Electrician
Agree too. Wouldn't be required on the line side either with no concentric or eccentric KO's.
 

Dsg319

Senior Member
Location
West Virginia
Occupation
Journeyman Electrician
Im going to have to disagree Rob. Although a BB is not specifically required on the line side of the service disconnect, some additional means besides a regular locknut is.
Are you meaning just a typical bushing or insulated throat connector for 4AWG and larger?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Im going to have to disagree Rob. Although a BB is not specifically required on the line side of the service disconnect, some additional means besides a regular locknut is.
That's true but that's not what I said. I stated that a bonding bushing is not required when there is no concentric or eccentric KO's. That is true because it could be a bonding locknut or bonding wedge.
 
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infinity

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Staff member
Location
New Jersey
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Journeyman Electrician
I meant bonding bushing. As indicated by the exchange between infinity and I, almost everyone jumps to bonding bushings when the extra bonding is required, but there are other options.
Yes thanks, you said it better than I did. :)
 

nickelec

Senior Member
Location
US
So just to be clear in this situation is anything but a locknut required. I will be using bushings. Just for good practice but is anything but a locknut required?

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texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
So just to be clear in this situation is anything but a locknut required. I will be using bushings. Just for good practice but is anything but a locknut required?

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As mentioned, on the line side of the service disco. if you have clean punched holes (no concentrics) you can use bonding locknuts to comply with 250.92. This can save a lot of labor and material cost as opposed to bonding bushings.
On the load side regular locknuts, with or without eccentrics are fine.
 
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Carultch

Senior Member
Location
Massachusetts
Are you meaning just a typical bushing or insulated throat connector for 4AWG and larger?
Unrelated to that rule. The rule for requiring bushings or insulated throat connectors for #4 and larger, is about protecting the insulation from abrasion. I don't agree with this rule, as I'd recommend a bushing or throat to protect the wire from abrasion, regardless of size.

The rule in question is about bonding, rather than mechanical protection of insulation. The fact that service raceways need more than just a standard locknut to establish the bonding of the raceway. Either a bonding locknut, bonding wedge, or bonding bushing. A rule specific to service raceways, as opposed to raceways in general.

On the load side regular locknuts, with or without eccentrics are fine.
250V to ground and less...yes.

Over 250V to ground, that would only be acceptable with a box that is listed for higher voltage bonding. Such as a 4S box, which will have a heavy duty knockout that is a lot more challenging to remove. Ordinary ring KO's that aren't listed otherwise, whether concentric or eccentric, are considered impaired continuity when Volts to ground nominal exceeds 250V. If you "use up" all the KO's in a group, it is treated as if they never existed in the first place.
 
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Josh111

Member
Location
USA
While we are on the topic, the terminology of bonding/grounding bushing vs bonding/grounding locknut is often swapped around. UL says that a a grounding bushing/locknut has the wire lug, while the bonding bushing/locknut doesn't. In reality many in the trade and some manufacturers call the bushing with the wire lug a "grounding bushing" and the locknut without the lug a "grounding locknut. Here's what UL says:

Grounding and Bonding Bushings Bonding bushings for use with conduit fittings, tubing (EMT) fittings, threaded rigid metal and intermediate metal conduit, or unthreaded rigid metal and intermediate metal conduit are provided with means (usually one or more set screws) for reliably bonding the bushing (and the conduit on which it is attached) to the metal equipment enclosure or box. They provide the electrical continuity required by the NEC at service equipment and for circuits rated over 250V. Means for connecting a grounding or bonding conductor are not provided and if there is need for such a conductor a grounding bushing should be used.

Grounding bushings for use with conduit fittings, tubing (EMT) fittings, threaded rigid metal and intermediate metal conduit, or unthreaded rigid metal and intermediate metal conduit have provision for the connection of a bonding or grounding wire or have means for mounting a wire connector available from the manufacturer. Such a bushing may also have means (usually one or more set screws) for reliably bonding the bushing to the metal equipment enclosure or box in the same manner that this is accomplished by a bonding bushing. Grounding bushings provide the electrical continuity required by the NEC at service equipment and for circuits rated over 250 V. They may be used with or without a bonding or grounding conductor as determined by the bonding or grounding function that is intended to be accomplished. Insulating throat liners in grounding or bonding bushings are suitable for temperatures of 150°C if they are black or brown in color. Unless otherwise marked, insulating throat liners of any other color are suitable for temperatures of 90°C.

Grounding and Bonding Locknuts — Grounding and bonding locknuts serve in a manner similar to grounding and bonding bushings except they do not provide abrasion protection for the conductor at the end of the conduit.
 

Carultch

Senior Member
Location
Massachusetts
While we are on the topic, the terminology of bonding/grounding bushing vs bonding/grounding locknut is often swapped around. UL says that a a grounding bushing/locknut has the wire lug, while the bonding bushing/locknut doesn't. In reality many in the trade and some manufacturers call the bushing with the wire lug a "grounding bushing" and the locknut without the lug a "grounding locknut. Here's what UL says:
What would be the point of what UL is calling a "bonding bushing", in contrast from a "grounding bushing"? The whole point of having anything other than a standard plastic bushing, or a plain metal bushing, is to enable connection of the EGC wire. Do you have an example photo that shows this distinction?

I've always seen the terms used interchangeably, and indicate a bushing that either integrates a grounding lug, or comes with a detachable grounding lug. I feel "bonding bushing" is a more accurate term that describes its purposes, just like "equipment bonding conductor" is a more accurate term for what we call an "equipment grounding conductor".
 

epelectric33

Member
Location
SD
Occupation
Electrical Consulting/Inspection/Master
So just to be clear in this situation is anything but a locknut required. I will be using bushings. Just for good practice but is anything but a locknut required?

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Need more information. Is the panel a stainless steel panel/galvanized panel/unpainted panel? If it is then no you do not need a bonding bushing as locknuts are UL listed for bonding but only on clean bare metal surfaces. If the panel is of a Painted or any type of coating kind then yes you will need a bonding bushing to bond the raceway (only on one end) if the raceway is of a metallic kind (which I am assuming it is because there is no reason to bond a non-metallic raceway).
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Need more information. Is the panel a stainless steel panel/galvanized panel/unpainted panel? If it is then no you do not need a bonding bushing as locknuts are UL listed for bonding but only on clean bare metal surfaces. If the panel is of a Painted or any type of coating kind then yes you will need a bonding bushing to bond the raceway (only on one end) if the raceway is of a metallic kind (which I am assuming it is because there is no reason to bond a non-metallic raceway).
This is not correct. Just because an enclosure is painted does not mean you need bonding bushings.
 

infinity

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Staff member
Location
New Jersey
Occupation
Journeyman Electrician
This is not correct. Just because an enclosure is painted does not mean you need bonding bushings.
I agree, have you ever seen bonding bushings on a painted cabinet or pull box with AC or MC-ap cable? The locknut is designed to cut the paint.
 

epelectric33

Member
Location
SD
Occupation
Electrical Consulting/Inspection/Master
I agree, have you ever seen bonding bushings on a painted cabinet or pull box with AC or MC-ap cable? The locknut is designed to cut the paint.
This is incorrect. The fittings are listed under UL 514b. If you read section 42 it tells you the testing procedure which describes what my first statement said. There is no way to guarantee that the device can cut the paint or coating due to there is not one specification on how many coats and such each manufacture installs. If your statement was correct then why would they produce Bonding lock rings/bonding Myers hubs/ Bonding Bushings? You can buff the paint off on both sides and not use one of the bonding styles and be in compliance (NEC 250.12). Now the raceway only has to be bonded on one side if it is continuous or can be bonded with externally with pipe bonding clamps (as long as it is bonded with the proper size conductor NEC 250.122 (branch)) and in this case you would not have to do the bonding in the panel. So to your point most MC terminations end up in a unpainted handy box or device box that will then have a bonding screw in them which thus bonds one side of the raceway.

Also, just because you have seen or done things for 30 years doesn't make it right.
 
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