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Old 01-26-2014, 04:54 PM   #1
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Cables from panel to protected location


I have a sub panel mounted on a barn wall, with a loft right above it. The panel currently supplies no circuits.
In the loft above it, there are vertical beams ever 12 - 20 feet or so where I could run the wire up through the barn ceiling/loft floor. However, the panel is dead-center between two of these poles, so if I run a wire from the panel directly up I'd be in the middle of the floor of the loft.

So, in order to run new circuits from the panel into the loft, I figured the best option would be to run PVC conduit from the top of the panel and along the barn ceiling until it can go up into the loft next to one of the poles. Two ways I'm thinking I can do this:

1) Get large conduit (1-in. or bigger), put a bushing on the end where it ends in the loft, and just run NM through it. Problems: Not sure if it will be too long such that I would have to apply the rules for conduit fill and derating (I'm thinking about 5 or 6 20amp circuits, and in the future possibly a 30amp or 50amp circuit)

2) Run THHN from the panel through the conduit and have a large junction box at the end in the pole in the loft where I can splice into NM (so I'd have to take conduit fill and derating into account)

I'd prefer Option #1, but I'm not sure if the conduit would be too long to be just protection of the NM.

Attached is a basic drawing (looking at it vertically).

Any ideas?
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Cables from panel to protected location-circuits.jpg  
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Old 01-26-2014, 05:04 PM   #2
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Cables from panel to protected location


Either way you will need to derate. You will not fit that many cables in a 1" conduit.
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Old 01-26-2014, 05:12 PM   #3
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Cables from panel to protected location


Okay, if I have to derate either way I was thinking about using THHN and running MWBC's so I have fewer current carrying conductors, then in the junction box on the end, separate each pair of MWBC's into 2 separate cables.

Also, found this...


312.5

Quote:
(C) Cables. Where cable is used, each cable shall be secured to the cabinet, cutout box, or meter socket enclosure.

Exception: Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure through one or more nonflexible raceways not less than 450 mm (18 in.) and not more than 3.0 m (10 ft) in length, provided all of the following conditions are met:

(a) Each cable is fastened within 300 mm (12 in.), measured along the sheath, of the outer end of the raceway.
(b) The raceway extends directly above the enclosure and does not penetrate a structural ceiling.
(c) A fitting is provided on each end of the raceway to protect the cable(s) from abrasion and the fittings remain accessible after installation.
(d) The raceway is sealed or plugged at the outer end using approved means so as to prevent access to the enclosure through the raceway.
(e) The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 6 mm (1/4 in.).
(f) The raceway is fastened at its outer end and at other points in accordance with the applicable article.
(g) Where installed as conduit or tubing, the allowable cable fill does not exceed that permitted for complete conduit or tubing systems by Table 1 of Chapter 9 of this Code and all applicable notes thereto.
Condition (g) seems to imply that if I'm just using it for physical protection I still wouldn't need to worry about conduit fill, but still the derating would pretty much destroy this prospect anyway since with enough circuits in there I'd have to put a junction box on the end anyway.

Any ideas for anything other than conduit that could protect the cables just from the panel and along the edge of the barn ceiling? (I mostly just don't want the look of all the cables on the wall)

Last edited by jhartz; 01-26-2014 at 06:38 PM.
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Old 01-27-2014, 02:34 PM   #4
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Cables from panel to protected location


Use a 1x6 or 1x8 as a running board. Staple cables to that, leaving room for 1x2s at both edges. After the cables are run, nail 1x2s to edges of the running board and then nail another board on top. This visually conceals the cables, and you can paint the wood if you want.
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Old 01-27-2014, 03:05 PM   #5
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Cables from panel to protected location


The cable fill issue would require a larger conduit. Also the conduit length cannot be more than 10'.
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Old 01-27-2014, 05:19 PM   #6
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Cables from panel to protected location


Hmm, the running board isn't a bad idea; sure would look nicer than 2" conduit (I think that's the biggest KO in the panel). I might go with that so I don't have to deal with derating, especially if I want to add more in the future that would push me over the derating cliff with conduit.
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Old 01-27-2014, 05:41 PM   #7
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Cables from panel to protected location


You could also run multiple conduits.
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Old 01-28-2014, 07:29 PM   #8
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Cables from panel to protected location


Thanks everyone. For now I'm going with the running board because it works well with the layout of the barn, but for future circuits in a different direction I will probably pull THHN through conduit.
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