Effective GFCP without bond bushing

J

jeg112

Member
Location
San Diego
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Inside Wireman
Copied and pasting here from YouTube comment section per Mike Holts request. Video was about bonding raceway to a bonded/grounded can.

"i know it's considered bonded by code but I'm saying the locknut and the shoulder of the connector are only making contact with the nonconductive paint on the enclosure. The electrical continuity occurs where the threaded portion of the connector happens to touch the unpainted area inside of the KO, yes? Is it fair to say we are relying on those two components making incidental contact for our effective gfcp?"
 
250.96(A) ... Any nonconductive paint, enamel, or similar coating shall be removed at threads, contact points, and contact surfaces or shall be connected by means of fittings designed so as to make such removal unnecessary.
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All locknuts are designed to make paint removal unnecessary. The UL testing requires the locknut be hand tightened and the rotated an additional 1/4 turn using a "hammer and screwdriver" or other suitable tool.
 
Do you happen to know the reference for that or the best place for me to look? I looked through UL 514B and found that exact wording (...hand tightened...1/4 turn...) but it was under the section for the sealing rings test so doesn't apply.
 
jeg112 said:
Do you happen to know the reference for that or the best place for me to look? I looked through UL 514B and found that exact wording (...hand tightened...1/4 turn...) but it was under the section for the sealing rings test so doesn't apply.
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so loosen the locknut after you have installed it and see if the locknut has cut through the paint.
 
So the main reason I ask is because we get these, for example, 36"x36" pullboxes sent from the shop prefabbed with all the connectors already installed. There are no splices in this one, so per 250.148 i had no intention to bond the can. As I was waiting for my colleague to shove the fish tape in, I noticed the paint around the connectors was pristine. It looked like they installed the connectors by wrench-tightening them from the outside. Fair enough, it looks nice, but that's when I started thinking about the effective GFCP and realized the only metal on metal contact was likely only going to be between where the threaded portion of the connector makes (or possibly doesn't make) incidental contact with the inner edge of the knockout. I tested continuity with my meter and some pipes rang out with perfect responsiveness while others seemed spotty. I got to thinking about what our industry standard is. A standard locknut - to my knowledge - is for mechanical purposes only, and is not considered a bonding device. Therefore, the shop's installation without scratching the paint is actually consistent with code and UL listing, and we as electricians are indeed relying on a potentially unreliable path in such scenarios. Does my concern make logical sense or am I missing something?
 
jeg112 said:
So the main reason I ask is because we get these, for example, 36"x36" pullboxes sent from the shop prefabbed with all the connectors already installed. There are no splices in this one, so per 250.148 i had no intention to bond the can. As I was waiting for my colleague to shove the fish tape in, I noticed the paint around the connectors was pristine. It looked like they installed the connectors by wrench-tightening them from the outside. Fair enough, it looks nice, but that's when I started thinking about the effective GFCP and realized the only metal on metal contact was likely only going to be between where the threaded portion of the connector makes (or possibly doesn't make) incidental contact with the inner edge of the knockout. I tested continuity with my meter and some pipes rang out with perfect responsiveness while others seemed spotty. I got to thinking about what our industry standard is. A standard locknut - to my knowledge - is for mechanical purposes only, and is not considered a bonding device. Therefore, the shop's installation without scratching the paint is actually consistent with code and UL listing, and we as electricians are indeed relying on a potentially unreliable path in such scenarios. Does my concern make logical sense or am I missing something?
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Use a continuity tester on each of the fittings to the box.
Does it squeal?
Good enough. Assuming the connector is tightened to the raceway.
 
jeg112 said:
So the main reason I ask is because we get these, for example, 36"x36" pullboxes sent from the shop prefabbed with all the connectors already installed. There are no splices in this one, so per 250.148 i had no intention to bond the can. As I was waiting for my colleague to shove the fish tape in, I noticed the paint around the connectors was pristine. It looked like they installed the connectors by wrench-tightening them from the outside. Fair enough, it looks nice, but that's when I started thinking about the effective GFCP and realized the only metal on metal contact was likely only going to be between where the threaded portion of the connector makes (or possibly doesn't make) incidental contact with the inner edge of the knockout. I tested continuity with my meter and some pipes rang out with perfect responsiveness while others seemed spotty. I got to thinking about what our industry standard is. A standard locknut - to my knowledge - is for mechanical purposes only, and is not considered a bonding device. Therefore, the shop's installation without scratching the paint is actually consistent with code and UL listing, and we as electricians are indeed relying on a potentially unreliable path in such scenarios. Does my concern make logical sense or am I missing something?
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All listed conduit fittings, including those supplied with locknuts, are listed as being part of the fault clearing path.
From the UL Guide Information for "Conduit Fittings (DWTT)":
All metal fittings for metal cable, conduit and tubing are considered suitable for grounding for use in circuits over and under 250 V and where installed in accordance with the NEC, except as noted for flexible metal conduit fittings and liquid-tight flexible metal conduit fittings.
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However section 6.2.1 of UL 514B, specifies how a locknut must be tightened for the required testing, including ground fault testing. It says to tighten the locknut hand tight and then an addition 1/4 turn using a hammer and flat-bladed screwdriver. It would be my opinion that if you tighten the connector body and not the lock nut, you have not tightened the fitting correctly. The turning of the locknut itself is to make sure that the teeth on the locknut cut through the paint on a painted enclosure. Turning just the connector will not do that.
 
Thanks for taking the time to get me that direct reference to the UL section. That's the exact kind of information I needed.
 
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