Bonding Bushings on eccentric KO's

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mkgrady

Senior Member
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Massachusetts
AHJ informed me that I missed a bond bushing between a MCB panel and a transfer switch.

I ran a metal offset nipple from a punched hole in the ats to an eccentric ko in the panel. He told me because some of the larger KO's remain in place I need the bond bushing. I responded that the KO's are eccentric and the lock nut is connected to can and not just the concentric rings. He responded that both concentric and eccentric KO's require a bond bushing. Is that true? If it is true, would adding an egc satisfy the requirement?

This makes me question whether or not running metal conduit anywhere while utilizing concentric KO's is compliant.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
They would have to be listed for grounding as most eccentrics are in small boxes

The odd thing is if you remove all the KOs and use reducing washers you don't need bonding as the reducing washers are listed for grounding. :roll:
 
infinity

infinity

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Location
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mkgrady said:
AHJ informed me that I missed a bond bushing between a MCB panel and a transfer switch.

I ran a metal offset nipple from a punched hole in the ats to an eccentric ko in the panel. He told me because some of the larger KO's remain in place I need the bond bushing. I responded that the KO's are eccentric and the lock nut is connected to can and not just the concentric rings. He responded that both concentric and eccentric KO's require a bond bushing. Is that true? If it is true, would adding an egc satisfy the requirement?

This makes me question whether or not running metal conduit anywhere while utilizing concentric KO's is compliant.
Click to expand...

What's the voltage? Less than 250 volt to ground no bonding bushing required even with eccentric KO's.
 
kwired

kwired

Electron manager
Location
NE Nebraska
Was the application by chance over 250 volts to ground?

Was too busy verifying and answer was already posted - no more "maybe" for 250 volts to ground and under. See 250.97 and exception in 2014 NEC.
 
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chris kennedy

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
iwire said:
The odd thing is if you remove all the KOs and use reducing washers you don't need bonding as the reducing washers are listed for grounding. :roll:
Click to expand...

Yup, you are correct.


"This is a NEC 110.3(B) issue. Reducing washers are certified (Listed) under Outlet Bushings and Fittings (QCRV), located on page 391 and 392 in the 2014 UL White Book and can also be found on UL Product Spec at www.ul.com/productspec and enter QCRV at the UL Product Category Code search field. The Guide Information for QCRV under the “Grounding” heading, states, “Metal reducing washers are considered suitable for grounding for use in circuits over and under 250 V and where installed in accordance with ANSI/NFPA 70, National Electrical Code. Reducing washers are intended for use with metal enclosures having a minimum thickness of 0.053 in. for non-service conductors only. Reducing washers may be installed in enclosures provided with concentric or eccentric knockouts, only after all of the concentric and eccentric rings have been removed. However, those enclosures containing concentric and eccentric knockouts that have been certified (Listed) for bonding purposes may be used with reducing washers without all knockouts being removed.” If the concentric or eccentric rings were not removed, you would need the bonding bushing to bond around those rings."
 
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mkgrady

Senior Member
Location
Massachusetts
iwire said:
They would have to be listed for grounding as most eccentrics are in small boxes

The odd thing is if you remove all the KOs and use reducing washers you don't need bonding as the reducing washers are listed for grounding. :roll:
Click to expand...

What would be an example of a box where the KO's are listed for grounding?
 
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mkgrady

Senior Member
Location
Massachusetts
kwired said:
Too add to that, if the raceway contains service conductors you need more then just standard locknuts to assure bonding of the raceway even if not concentric/eccentric KO's and at any voltage.
Click to expand...

That really makes SEU cable and PVC conduits attractive when doing a service.
 
hacim23

hacim23

Journeyman Electrician
Location
washington, DC
Occupation
Electrician
bond bushings on eccentric

bond bushings on eccentric

this question just came up on my job so I searched and found this thread.

So over 250v with eccentric requires a bond bushing right?

my example is a 480v, 30a service disconnect feeding an exhaust fan.
 
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