Article 250.92 B-3 NEC

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dsullada

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I need an expert opinion on the meaning of 250.92 B-3 which says that "threadless couplings and connectors where made up tight for metal raceways" are an acceptable method of bonding at service equipment". The paragraph after method B-4 says that bonding jumpers are required around eccentric and concentric KO's, then the last sentence says "Standard locknuts or bushings shall not be the sole means for the bonding required by this section". It is my understanding from this, and that of my engineering consultant, that this means a steel EMT connector made up tight to an enclosure is an acceptable method of bonding service equipment together and bonding the grounding electrode conductor raceway to the enclosure.
I am currently on a job where the inspector disagrees. They interpret the sentence that standard locknuts or bushings are not allowed as the sole means of bonding to apply to section B-3 also. Contrary to what B-3 says, they claim I need grounding bushings on EMT connectors connecting a 1600A 480-V Utility Section and the Main disconnect section as well as on the EMT connector connecting the ground electrode conduit. I have tried to point out to them that if this were true, then 250.92 B-3 is erronious and the requirement to bond around concentric KO's is superflous as it means you have to bond around everything anyway. The pictures in the NEC Handbook on this section seems to confuse rather then help them. They indicated if I could produce an expert opinion supporting my understanding they would consider it. HELP!!!

dsullada
Nor Cal Electric Co.
Contracting 48 years
 
I think the inspector is correct.

You can use the thread-less connectors but you can not use just the standard lock nut that comes with them.
 
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I agree with MPD. When a rigid conduit lands in an enclosure, only the two locknuts are in direct contact with the enclosure.

Whereas when a connector lands in an enclosure, the connector itself is in direct contact with the enclosure, not just the locknut.

That's why the "made up tight" part comes into play; the locknut itself is not the "sole means of bonding" the conduit.
 
LarryFine said:
That's why the "made up tight" part comes into play; the locknut itself is not the "sole means of bonding" the conduit.
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Are you saying that I can use no more than a standard lock nut with a thread-less connector just as long as the connector hits the can tight?

If so I disagree.

The "made up tight" part has to do with how the connector is connected to the raceway.
 
iwire said:
Are you saying that I can use no more than a standard lock nut with a thread-less connector just as long as the connector hits the can tight?

If so I disagree.

The "made up tight" part has to do with how the connector is connected to the raceway.
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I agree with Bob. The grounding locknut, wedge or bushing requirement would still apply.
 
So, what does . . .
dsullada said:
250.92 B-3 which says that "threadless couplings and connectors where made up tight for metal raceways" are an acceptable method of bonding at service equipment".
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. . . mean?
 
250.92 B-3 which says that "threadless couplings and connectors where made up tight for metal raceways" are an acceptable method of bonding at service equipment".
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How would you attach a threadless coupling to the service equipment?
 
In the 96 code the words "standard locknuts or bushings shall not be the sole means for the bonding required by this section" were only found in what is now 250.92(B)(3). The panel action on comment 5-152 in the 98ROC moved those words out of the "theadless couplings and connectors" subsection to the beginning of the section. In the 96 and earlier codes the ban on using standard locknuts for service bonding only applied to threadless connectors. The wording was relocated to make it clear that the prohibition applies to all service raceway terminations, both threaded and threadless.
Don
 
dsullada said:
Obviously the coupling continues the electric bond throughout the run.
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Yes, exactly, and I am sure that was Trevor's point. :cool:

Thread-less couplings and connectors 'made up tight' can be used as the means to continue the electrical bond from 'conduit to conduit' as with a coupling OR from 'conduit to pipe threads' as with a connector.

However the bonding connection between the thread-less connectors pipe threads and the enclosure can not be done with a standard lock nut.

The continuation of the electrical bond from the enclosure to the thread-less connector must use some sort of listed bonding device.
 
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