PVC Conduit Fill At SEP

[CNewhouse]

Evening,

I am correct in my understanding that typical conduit fill and derating guidelines don't apply to a short PVC nipple below the service panel? The PVC was installed to protect the NM home runs as they penetrate the exterior wall, is probably near 24" long, and is obviously open at the crawlspace end (not running between 2 boxes). Any reason for concern here? I'm having difficulty locating a reference to this specific situation.

[Jim Katen]

As long as it's less than 24" long, it's not a concern. 

310.15(B)(3)(a)(2) Adjustment factors shall not apply to conductors in raceways having a length not exceeding 24".   

[mtwitty]

Conduit nipples (24" or less) can be filled to 60%. Your photo appears to definitely exceed that. It is a common violation that is overlooked and accepted. It's usually not really a big concern.

 

[Jim Katen]

It's my impression that the 60% rule in Chapter 9 only applies when the conduit is enclosed at each end by a "box, cabinet, or similar enclosure." No? 

[CNewhouse]

10 minutes ago, Jim Katen said:

It's my impression that the 60% rule in Chapter 9 only applies when the conduit is enclosed at each end by a "box, cabinet, or similar enclosure."

That is what I was thinking as well.

[mtwitty]

1 hour ago, Jim Katen said:

It's my impression that the 60% rule in Chapter 9 only applies when the conduit is enclosed at each end by a "box, cabinet, or similar enclosure." No? 

I don't think so by looking at 312.5(C) exceptions. #7 exception still requires conductor fill requirements for conduit sleeves 18 inches to 10 ft. in length. Typically, sleeves are open on both ends, and do not have fill requirements. This exception allows a "sleeve" to be connected to the top of the enclosure and open on the other end, but still must meet fill requirements. Other violations in Charley's photo include no fastening of the cables on the outer end of the sleeve (exception #1), and no fitting on the end of the conduit, and/or plugging the outer end. (exceptions # 3 &4) I know I got rejected for this several years ago for "too many cables" in a nipple/sleeve connected to the top of the panel. I could be wrong (usually am) but that's how I interpret this.

 

[mtwitty]

Charley, does the conduit attached to the panel? Looks like it comes in at the bottom.

[CNewhouse]

Yes. It connects at the bottom right of the panel.

[mtwitty]

10 hours ago, CNewhouse said:

Yes. It connects at the bottom right of the panel.

In that case, I'm assuming there is an LB to turn up to the bottom of the enclosure? If so, that puts the NM cables in a wet location, which is a violation and a larger concern than the overfill, in my opinion. LB fittings can be water holding reservoirs when the seals leak. It depends on how picky you want to be, but the installation is non-compliant on several fronts. 312.5(C) has 7 conditions that all must be met, and from what I can see and understand from your explanation, it fails to meet 5 of those. Also, non flexible raceways not less than 18 inches and not more than 10 feet in length with NM cables into enclosures are only allowed to enter from the top. 

[CNewhouse]

Yes, there is an LB conduit body below the panel.  I actually emailed Cantex asking if the conduit body is rated for exterior installation (I know some are not). Here is the response, which doesn't actually answer the question:

"This is pretty much a standard installation for the conduit bodies.  With the gasket, between the body itself & the lid, if properly secured, it should remain watertight under normal rain conditions and/or sprinkler action."

Is this something you would comment on as a defect, Mike? The gasket was a bit degraded, but the interior of the conduit body was dry despite recent rainfall. 

[mtwitty]

4 hours ago, CNewhouse said:

Yes, there is an LB conduit body below the panel.  I actually emailed Cantex asking if the conduit body is rated for exterior installation (I know some are not). Here is the response, which doesn't actually answer the question:

"This is pretty much a standard installation for the conduit bodies.  With the gasket, between the body itself & the lid, if properly secured, it should remain watertight under normal rain conditions and/or sprinkler action."

Is this something you would comment on as a defect, Mike? The gasket was a bit degraded, but the interior of the conduit body was dry despite recent rainfall. 

 

 

The LB is not really the issue...it's what's inside of it. The interior of a raceway (conduit) in a wet location is considered to be a wet location. NM cable is not allowed/rated for use in wet locations. NM cable can break down over time if subjected to water. If water gets in a conduit or conduit fitting, it can stay for a long time. I actually had a trouble call yrs. ago with an installation very similar to the one you posted. A breaker was tripping on a circuit. When I opened the LB, water ran out. The conduit was half full of water. The wire insulation probably had minor nicks or cracks that developed over time and caused a short. If I had not experienced this personally, I probably would think the likelihood of a problem would be rare; and in most cases, it would be, but for that reason, I always report NM in wet locations as a concern, particularly when it is in conduit. In your case, I would probably just explain the potential issues that could arise from the improper installation, recommend sealing the open end of the conduit in the crawl space, keeping a good gasket/seal on the LB cover, and carry on.

Edited December 21, 2019 by mtwitty

[CNewhouse]

Understood. Thanks Mike.