correct installation of EMT connectors

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moo2380

Member
Location
CT
Occupation
Master Electrician
Recently I was ?shot down? on an inspection by an Electrical Inspector in the county in which I work as a result of what he says is an incorrect installation of a few of my EMT connectors.

The problem;
When I installed the conduit run, the EMT connectors on one side of the run did not sit flat onto the cabinet. The locknut sits at ~1/8 of inch above the cabinet on one side and touching on the other side. The Inspector claims that since the conduit is used as a EGC, if a fault condition occurred on that circuit it would create a high resistance fault and would not clear the fault quickly. My argument is that as long as the connector is tight, even though the locknut is not fully touching the surface of the cabinet, then I have fulfilled the requirements of the NEC, 358.56. The Inspectors argument is that the connector is not ?Listed? for that purpose (must be installed so that the connectors sits flat against the metal cabinet).

I?m I correct in assuming that this installation is code complaint?
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
moo2380 said:
When I installed the conduit run, the EMT connectors on one side of the run did not sit flat onto the cabinet. The locknut sits at ~1/8 of inch above the cabinet on one side and touching on the other side.

I would guess that the connectors where intended to sit flat on the cabinet. 110(3)(B).

What size EMT and how did it get so far off?
 

iwire

Moderator
Staff member
Location
Massachusetts
I would put bonding bushings on and move on.

I bet if you ask UL they will say that they never tested it for grounding as you have it installed.
 
I will help with the unanimous trend here...
The fittings are tested when the shoulder of the fitting and the locknut are making full contact with the enclosure. If they are not, who knows how the fitting will act as part of the effective ground fault current path.
 

EBFD6

Senior Member
Location
MA
I will agree with everyone else, with no facts to back up my opinion.

The connector should be flat to the outside of the enclosure, the locknut should be flat to the inside of the enclosure and tight.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Mr. Moo, exactly why are the locknuts not sitting square to the enclosure? Maybe the locknuts were threaded tilted, and just replacing them would work. Are the connectors themselves likewise askew? Are we talking 1/2's and 3/4's, or 2" and up?
 

moo2380

Member
Location
CT
Occupation
Master Electrician
The conduit run is for a 1200A feeder circuit, I under bent the 90 and tightened down on the locknut but cabinet wouldn’t conform to the EMT connector, big money to change now. My thoughts are that as long as the EMT connectors locknut was in contact with a couple of the “tabs” from the locknut and the it’s tight, than it would be ok. The Inspector couldn’t support his claim with a “listing” of the product which might defend his position on the “correct” installation, so then as long as the connector is “tight” then why wouldn’t it be able to clear a fault. I think that maybe the Inspector might be a little “Nit Picky”, or maybe I missed something to be fair, I’m not sure.?

As far as testing the equipment, is there a standard that dictates an EMT connectors grounding performance when installed with partial surface contact or full surface contact as long as the contact is "tight"?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
moo2380 said:
The conduit run is for a 1200A feeder circuit, I under bent the 90 and tightened down on the locknut but cabinet wouldn?t conform to the EMT connector, big money to change now.
I would work on tightening that locknut some more. Maybe you can persuade the cabinet wall to conform a bit more.
 

iwire

Moderator
Staff member
Location
Massachusetts
moo2380 said:
My thoughts are that as long as the EMT connectors locknut was in contact with a couple of the ?tabs? from the locknut and the it?s tight, than it would be ok.

It would probably work fine, but it was never tested that way (or at least it would surprise me if it was)

As far as testing the equipment, is there a standard that dictates an EMT connectors grounding performance when installed with partial surface contact or full surface contact as long as the contact is "tight"?

Sure, the listing agencies will have very detailed testing standards. It would surprise me very much if any of them cover the type of installation you describe.
 

Buck Parrish

Senior Member
Location
NC & IN
Yeah the inspector has you on the listing.

Although only one side of the conduit is required to have grounding lock nuts or grd. bushing.
 

ceb58

Senior Member
Location
Raeford, NC
moo2380 said:
The conduit run is for a 1200A feeder circuit, I under bent the 90 and tightened down on the locknut but cabinet wouldn?t conform to the EMT connector, big money to change now.

Why did you not fix it at the time. The cabinet shouldn't have to "conform" to a crooked bend.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
LarryFine said:
I would work on tightening that locknut some more. Maybe you can persuade the cabinet wall to conform a bit more.

You would be working on a cross thread Larry, but I'm guessing you know that.
 

tonyou812

Senior Member
Location
North New Jersey
ceb58 said:
Why did you not fix it at the time. The cabinet shouldn't have to "conform" to a crooked bend.
My thoughts exactly. Why leave it that way? Not only is it asking for trouble it just looks like a bad install in my opinion. That would personally drive me crazy looking at a crooked connector for the whole world to see.
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
iwire said:
I bet if you ask UL they will say that they never tested it for grounding as you have it installed.

UL also lets Jedi think outside the box.

Modify a sealing locknut as spacer outside the box. File locknut wedge angle so all connector surfaces mate flush with box.

If inspector isn't delighted, point to White Book; UL CONDUIT FITTINGS (DWTT) & (QCRV). Wedged bushing is still intended for use as "Insulating Bushing", not as locknut.
 

LJSMITH1

Senior Member
Location
Stratford, CT
UL514B governs the design, construction, and testing of ALL EMT fittings. All testing with EMT connectors is done with the connector flange fully seated through the knocout and touching the enclosure wall. Then, the locknut is threaded on hand-tight PLUS 1/4 turn. The locknut should be contacting the same enclosure wall inside around the 360 surface of the locknut (or on each lug if you have that kind of locknut design).

If the connector is off center or tilted in the box, there will be no way to fully secure the fitting and guarantee proper bonding to the enclosure wall. UL 514B does not have a specific test to validate that this condition is acceptable, however, common sense would indicate that it is not.

Depending on the trade size (lets say 2"), UL514B Sec. 8.9 and Table 21 Current Test, requires the fitting to handle 3900A for 6 seconds without arcing or other noticable damage. In my experience, an incorrectly assembled fitting or under-torqued locknut would cause the fitting to fail this test. I could almost bet that a locknut only touching on 1/2 or less of its face surface or lugs will have much lower current carrying capability than one correctly assembled and torqued.

You could use a bonding bushing as suggested, which should satisfactorily address the bonding issue (as long as your AHJ approves).
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
How are you bushing the conduit?

If you only have the lock nut on a few threads then you're probably not able to screw on a plastic or bonding bushing too.
 

moo2380

Member
Location
CT
Occupation
Master Electrician
LJSMITH1 said:
UL514B governs the design, construction, and testing of ALL EMT fittings. All testing with EMT connectors is done with the connector flange fully seated through the knocout and touching the enclosure wall. Then, the locknut is threaded on hand-tight PLUS 1/4 turn. The locknut should be contacting the same enclosure wall inside around the 360 surface of the locknut (or on each lug if you have that kind of locknut design).

If the connector is off center or tilted in the box, there will be no way to fully secure the fitting and guarantee proper bonding to the enclosure wall. UL 514B does not have a specific test to validate that this condition is acceptable, however, common sense would indicate that it is not.

Depending on the trade size (lets say 2"), UL514B Sec. 8.9 and Table 21 Current Test, requires the fitting to handle 3900A for 6 seconds without arcing or other noticable damage. In my experience, an incorrectly assembled fitting or under-torqued locknut would cause the fitting to fail this test. I could almost bet that a locknut only touching on 1/2 or less of its face surface or lugs will have much lower current carrying capability than one correctly assembled and torqued.

You could use a bonding bushing as suggested, which should satisfactorily address the bonding issue (as long as your AHJ approves).


That makes absolute sense, even though the code allows for this installation (i.e. skewed EMT connectors) ?tight?.

However if the Inspector wanted to push the issue he probably could call it a violation of 110.3 incorrect installation according to the listing and labeling..?? Although he would have to produce from the MFG the listing of the connector which would have to indicate the proper installation of the connector as it?s designed.

I?m probably going to lose this one, but since the explanation of the test criteria surrounding UL 514B this makes sense.
 
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