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Old 11-13-2008, 11:07 AM   #1
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NM to ENT for Panel


HI;

I want to make my new sub panel connections look really nice. I don't really want to run any NM below the joists to connect into the top of the panel. I want it to all be conduit. My question is, if I run conduit from the panel to up between the joists, and put a NM clamp on the end, can I just run one piece of NM in each conduit? and do I strip the NM the entire legenth of the conduit? (2-3 feet until it connects into the panel)

The conduit NM clamps I have are just designed for 1 piece of NM, so I am not sure if I could have a couple pieces in a larger conduit or not.

Any other suggestions on getting the NM into my box and keeping it all nice and clean?

Thanks
Jamie

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Old 11-13-2008, 11:13 AM   #2
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NM to ENT for Panel


I think your supposed to leave the sheath on the entire conduit length, and then strip at the other end. You leave about 1/4" of sheath at the end. But I'd have to check it again. Somebody correct me if I'm wrong?


You could staple it cleanly in small bundles, be sure not to bundle the wires to much. If you do, you have to derate.

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Old 11-13-2008, 03:59 PM   #3
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Quote:
Originally Posted by jamiedolan View Post
HI;

I want to make my new sub panel connections look really nice. I don't really want to run any NM below the joists to connect into the top of the panel. I want it to all be conduit. My question is, if I run conduit from the panel to up between the joists, and put a NM clamp on the end, can I just run one piece of NM in each conduit? and do I strip the NM the entire legenth of the conduit? (2-3 feet until it connects into the panel)

The conduit NM clamps I have are just designed for 1 piece of NM, so I am not sure if I could have a couple pieces in a larger conduit or not.

Any other suggestions on getting the NM into my box and keeping it all nice and clean?

Thanks
Jamie


If you can meet ALL of these requirements then your good to go.


(C) Cables
Where cable is used, each cable shall be secured to the cabinet, cutout box, or
meter socket enclosure.
The main rule of 312.5(C) prohibits the installation of several cables bunched together
and run through a knockout or chase nipple. Individual cable clamps or connectors are
required to be used with only one cable per clamp or connector, unless the clamp or
connector is identified for more than a single cable.
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.

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Old 11-13-2008, 04:22 PM   #4
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NM to ENT for Panel


required to be used with only one cable per clamp or connector, unless the clamp or
connector is identified for more than a single cable.

I Read this to mean: If I am going to use the clamp entry method on the top of the panel - then I need to just find cable clamps that are rated for multiple pieces of NM, not just the normal box clamps.

(a) Each cable is fastened within 300 mm (12 in.), measured along the sheath, of the
outer end of the raceway.

This means; A wire staple to the joist within 12 inches of the top of my conduit?

(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.

A screw on bushing.

(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.

I can't figure out what this means, How do you seal the raceway that has NM wires in it??

(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.

So do I look at the chart and calculate this out the same way we did with THHN? If I use some 2" conduit, I assume that I can put a number of pieces of NM into it before it needs to be derated?

If I understand this correctly, NM can never enter the box anywhere but the top, wether it is connected directly with clamps or if it is through the chase / conduit?

However, THHN can enter the box in ridgid conduit anywhere (back sides, top bottom) correct?

Thanks

Jamie
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Old 11-13-2008, 04:25 PM   #5
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I don't believe (g) applies to you since it's not a complete conduit system, just a sleeve. So you can fill to 100% if the other requirements are met.

Someone correct me if I'm wrong.
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Old 11-13-2008, 04:34 PM   #6
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Quote:
Originally Posted by jamiedolan View Post
....How do you seal the raceway that has NM wires in it?...
Ever hear of Great Stuff foam? Squirts out of a long nozzle, just like whipped cream!

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Old 11-13-2008, 04:37 PM   #7
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Ever hear of Great Stuff foam? Squirts out of a long nozzle, just like whipped cream!

Yes, I have used much of it. However, it sounds like a horriably messy solution to close up the wires. How do you add anything new to the conduit? I guess you don't.
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Old 11-13-2008, 04:40 PM   #8
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What sort of screw on fitting for ENT did you have in mind?? I don't think a thing exists. You don't really need to protect cables from abrasion with ENT though, the ENT isn't going to abrade them.
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Old 11-13-2008, 04:43 PM   #9
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Quote:
Originally Posted by Gigs View Post
What sort of screw on fitting for ENT did you have in mind?? I don't think a thing exists. You don't really need to protect cables from abrasion with ENT though, the ENT isn't going to abrade them.

I don't know. I agree that the ENT is not really likely to cause problems. I am concerned about this part of the code:

"(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."



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Old 11-13-2008, 04:45 PM   #10
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Quote:
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..... How do you add anything new to the conduit?....
Easy. Simply poke a hole thru the foam with a large screwdriver, and you will be able to insert another cable with ease.
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Old 11-13-2008, 05:40 PM   #11
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Quote:
Originally Posted by jamiedolan View Post
I don't know. I agree that the ENT is not really likely to cause problems. I am concerned about this part of the code:

"(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."
This seems like a lot of hassle for something that's basically cosmetic. Neatly arranged NM coming out of the top of your panel in proper clamps looks pretty good.
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Old 11-13-2008, 05:47 PM   #12
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Quote:
Originally Posted by Gigs View Post
This seems like a lot of hassle for something that's basically cosmetic. Neatly arranged NM coming out of the top of your panel in proper clamps looks pretty good.
I agree, I just use stak-its above the panel for my installs.

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