Bonding Conduits

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jester40

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In a electrical room where, all feeds to sub panels is underground in pvc pipe, and then converted to emt to run up the wall into the panel tubs, and the emt conduit enters thru drilled/punched holes, do I need to use bonding bushings, or is the lock nut and shoulder on the emt fitting enough?:-?
 
dcspector said:
Bob, bonding bushings are only required at the service 250.92(B) ko's aren't they? This has always been confusing to a lot of Electricians and spectors.
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Greg, see 250.97

On less than 250V to ground the Code seems to be silent and that has always puzzled me. The higher the voltage, the more current you can get to flow through a fixed resistance. it's all about sending enough current through fuse or breaker to cause it to open right?

So on 208Y/120 it seems as though the Code permits oversize KO's without additional bondong means?????

I may get flamed for this, but on 208Y/120 systems if the KO is oversized or the concentric is badly mangled or the shoulder does not seat firmly I ask for a bonding bushing. If the metal raceway contains an EGC I ensure that at least one end of the raceway is properly bonded. If the metal raceway is the EGC, then both ends need to be properly bonded.

Oh and I can't resist this one: "before I could'nt even spell the word "spector" now I are one" I hope you have a good sense of humor Greg!!
 
sandsnow said:
I may get flamed for this, but on 208Y/120 systems if the KO is oversized or the concentric is badly mangled or the shoulder does not seat firmly I ask for a bonding bushing. If the metal raceway contains an EGC I ensure that at least one end of the raceway is properly bonded. If the metal raceway is the EGC, then both ends need to be properly bonded.
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I will not flame you I have to ask what gives you the authority to ask for more than the NEC.

UL even lists reducing washers as suitable for grounding.

That being the case unless a specific NEC section can be cited IMO you are asking for more than I have to give.
 
I would point to 250.96(A) which states:
Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non?current-carrying parts that are to serve as grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be effectively bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them.

I've seen concentric KO's so mangled that there is one little tab barely hanging on to the enclosure or people who don't have a KO set and use the wrong size hole saw that gives a hole that the locknut tabs can barely grab.

If the connector is off plumb just a little then the shoulder and the locknut will not seat firmly on the wall of the enclosure.

I think those cases the conduit would not be effectively bonded as stated in the above section.
 
sandsnow said:
I've seen concentric KO's so mangled that there is one little tab barely hanging on to the enclosure or people who don't have a KO set and use the wrong size hole saw that gives a hole that the locknut tabs can barely grab.

If the connector is off plumb just a little then the shoulder and the locknut will not seat firmly on the wall of the enclosure.

I think those cases the conduit would not be effectively bonded as stated in the above section.
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While I agree with your reasons I disagree it's within an inspector authority to demand it.

Bit if you asked me I would likely comply......but than again I use the right size tools and if a concentric is shaky I install reducing washers right on top of it. :smile:
 
Poor installation is not meeting the code. I f the concentric KO is all mangled and ready to fall out I would think this is not meeting the minimum requirements of the NEC. I have been asked to make sure the paint on the box is cleared off to make for a solid connection.
 
Bob,
So if I can't demand it, then I guess i would be exceeding my authority in your mind.

To me if I'm exceeding my authority, then I'm requiring something above the Code. In other words, the installation as is complies with the Code.

So if a concentric KO is barely hanging on, then that is "effectively bonded" per 250.96(A)???

It must be, you feel that I am exceeding my authority or have no authority to demand a bond bushing there.

Bob, surely you jest!?!?!?! Oh say it ain't so!!!! (I can't do those cute little smileys here)
 
I see what Bob is saying calling more than NEC requirements but if the intent of the code does not meet then Larry I agree......and yes I have a crazy sense of humor Larry,spector
 
sandsnow said:
So if a concentric KO is barely hanging on, then that is "effectively bonded" per 250.96(A)???
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Larry If it is really 'barely hanging on' putting a bonding bushing on it will not secure it.

IMO if the installation is that poor that the connectors can not work as the NEC and UL expects for grounding than there is an installation problem that would be better addressed with one or more of the following.

300.10

300.12

344.42

358.42

Understand I am not disputing that some KOs are junk I just feel you may be approaching it from the wrong direction.
 
Bob in that senario if a bond bushing was installed set screw to threads and the jumper to cabinet, enclosure, etc. that would indeed set a proper fault path regardless of an improper install as mentioned....would'nt it?
 
dcspector said:
if a bond bushing was installed set screw to threads and the jumper to cabinet, enclosure, etc. that would indeed set a proper fault path regardless of an improper install as mentioned....would'nt it?
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Of course it would.

But it would also be ignoring the real issue of the sloppy work.

Cite one of the sections I posted and make them fix the problem.

From 358.42

Couplings and Connectors used with EMT shall be made up tight.
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If the connector is barely hanging on it is not IMO tight.

Than there is 300.10 which specifically requires effective electrical continuity of raceways.
 
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