Conduit Question

[Bob NH]

Here's an interesting thread from another forum on a related topic. After reading it, all I got was a headache, and I still don't know why you can't use Romex in conduit.

http://ths.gardenweb.com/forums/load...003331911.html

You are not prohibited from using NM in conduit; you ARE prohibited from using it in a wet LOCATION.

Romex (Nonmetallic, NM cable) often has paper wrapping inside and is not required to be resistant to water. Therefore, you can't use NM cable in any wet location.

An underground location is considered wet, even if in "waterproof" conduit.

[jwelectric]

Okay, I got it.

But can you explain why individual conductors (inside conduit) like THHN-THWN are safer in locations exposed to weather than Romex (inside conduit)?

310.8(C) Wet Locations. Insulated conductors and cables used in wet locations shall be
(1) Moisture-impervious metal-sheathed;
(2) Types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THHW-2, THWN, THWN-2, XHHW, XHHW-2, ZW; or
(3) Of a type listed for use in wet locations.

The conductors in NM cable are only required to be rated at 90 degrees and no marking is required on the conductors theirself therefore they can not be installed in a Wet Location.

[jbfan74]

Actually Mike this cutter will not do as you say. Although I have not used one personally yet it does seem to live up to it's reputation.
It is made specifically for EMT. It is NO ordinary tubing cutter.

I have one and use it of the time. It was a little hard to get used to it, to know how far to cut.
You score the cut, then snap the pipe. It does not work well on short pipe, because you don't have much to hold when snapping.

[Verdeboy]

1. Can you use this outside (above ground) or do you need the kind with PVC coating for outdoor use?

2. What's the best way to cut it?

3. Do they make outdoor boxes specifically designed to connect flex conduit?

[jwelectric]

1. Can you use this outside (above ground) or do you need the kind with PVC coating for outdoor use?

2. What's the best way to cut it?

3. Do they make outdoor boxes specifically designed to connect flex conduit?

348.12 Uses Not Permitted.
FMC shall not be used in the following:
(1) In wet locations unless the conductors are approved for the specific conditions and the installation is such that liquid is not likely to enter raceways or enclosures to which the conduit is connected
(2) In hoistways, other than as permitted in 620.21(A)(1)
(3) In storage battery rooms
(4) In any hazardous (classified) location other than as permitted in 501.10(B) and 504.20
(5) Where exposed to materials having a deteriorating effect on the installed conductors, such as oil or gasoline
(6) Underground or embedded in poured concrete or aggregate
(7) Where subject to physical damage
348.20 Size.
(A) Minimum. FMC less than metric designator 16 (trade size ½) shall not be used unless permitted in 348.20(A)(1) through (A)(5) for metric designator 12 (trade size ).
(1) For enclosing the leads of motors as permitted in 430.245(B)
(2) In lengths not in excess of 1.8 m (6 ft) for any of the following uses:
a. For utilization equipment
b. As part of a listed assembly
c. For tap connections to luminaires (lighting fixtures) as permitted in 410.67(C)

[Verdeboy]

Thanks,

This is almost as complicated as the tax code, but a lot more interesting.

[frenchie]

I think I may have posted this before, but just in case I didn't? Online access to the NEC:

http://www.nfpa.org/freecodes/free_a...ookie%5Ftest=1

It's good bedtime reading, anyways. Hard to stay awake through more than a couple of pages!

...that link is courtesy of Joe T., believe it or not.

[Chris75]

http://www.nfpa.org/freecodes/free_a...ookie%5Ftest=1

Here is the 2008 edition...