250.97??

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jes25

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The way I am understanding bonding for over 250V is that you need to use bonding bushing around ringed KO's. We are refered to 250.92 which only requires assured bonding on 1 end of the raceway.

So if I ran a piece of MC from a panel with ringed KO's to a box with KO's listed for grounding (see exception 250.97) would I need the bonding bushing on the panel end? Or is the raceway code complianlty bonded via the listed KO's on the box ends?

I see a lot of guys installing a ground wire for 480/277 circuits but not using a bonding bushing to bond the raceway itself I see this as a violation anyone agree?
 
Unless the MC jacket were listed as an EGC (only some very new MC cable is) it wouldn't require a bonding bushing if the KO's were eccentric or concentric and not listed for bonding over 250 volts.
 
infinity said:
Unless the MC jacket were listed as an EGC (only some very new MC cable is) ...
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Not to thread hi-jack....but...

Is the MC that is listed as EGC disquinshable (sp?) from the typical MC by some means AFTER it is installed? ie, a green strip or something?
 
celtic said:
Not to thread hi-jack....but...

Is the MC that is listed as EGC disquinshable (sp?) from the typical MC by some means AFTER it is installed? ie, a green strip or something?
Click to expand...


Good question. I've never seen it. Still see alot of the blue stuff.
 
So the intent of 250.97 is to assure the connected equipment (ie: light fixture) is connected to a solid EGC, and not to bond the raceway itself. Or both?

Consider the EMT pipe run with ringed KO's. If I install a EGC inside the pipe do I not have to bond it the pipe itself, to assure the raceway is bonded.


To clarify things here, I understand the required use of a bonding jumper and bonding bushing when using the EMT as the the EGC. These questions are relating to bonding the raceways when a EGC is installed in addtion to the EMT.
 
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Consider the EMT pipe run with ringed KO's. If I install a EGC inside the pipe do I not have to bond it the pipe itself, to assure the raceway is bonded.
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IMO this section is rather vague. Here's what Mike Holt has to say:


"Metal raceways or cables, containing 277v or 480 v circuits, terminating at ringed knockouts must be bonded to the metal enclosure with a bonding jumper sized in accordance with table 250.122...."
 
infinity said:
IMO this section is rather vague.
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I think it is vague as well. I spent about 20 minutes analyzing every word of 250.97 and using the mike holt book.

Around here standard operating procedure is to install a ground wire if you have 277/480 circuits with no bonding bushings involved.

If the intent here is to bond the raceways then I think you would need the bonding bushings even on MC wiring methods to bond the metal cable sheath. Any inspectors see it like me?

I hope I am wrong.
 
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