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#50292 03/29/05 08:52 PM
Joined: Aug 2004
Posts: 186
N
Member
What size EMT, & PVC would be used if you were going to run on 30 amp 220 volt circuit. the run would be 10/2 romex pushed through this. I have been told that it requires 3/4" but every thing i have ever been tought tells me 1/2 would be fine. It is 2 conductors and a ground all solid 10awg copper. These hit a weather proof box befor going to pipe, it it required to strip down the romex from its outer jacket pprior to being fished.

#50293 03/30/05 04:23 PM
Joined: Dec 2003
Posts: 751
E
Member
Why would any sane electrician strip down a length of NM cable, instead of simply pulling the individual conductors?

To address your question: Chapter 9, Table 1 of the NEC, note 9 requires us to consider the cable as a single circular conductor with a diameter equal to the largest dimension of the cable. 53% fill.

What is the largest dimension of 10/2 Romex? using Table 4 for PVC, I see, for the 53% column, a maximum area of .151 sq. in. for 1/2 inch and .269 sq. in. for 3/4 inch conduit.
Doing the math, for 1/2 inch PVC conduit the maximum size would be .438 inches, and for 3/4 inch PVC the maximum size would be .585 inch.
I do believe to sleeve 10/2 we would need 1 inch PVC to meet code. Has anyone measured 10/2 Romex lately?


Earl
#50294 03/30/05 04:29 PM
Joined: Apr 2004
Posts: 156
R
Member
Save yourself much pain and foul language and change over to THHN in a 1/2". Running romex through EMT is like driving a tractor trailer in a parking garage, not worth the trouble.

#50295 03/30/05 10:36 PM
Joined: Apr 2002
Posts: 914
E
Member
Skip the formulas and go to annex C for ENT. Use THHN and it says 4 #10 conductors in 1/2", so 10/2 is OK.

#50296 03/30/05 11:19 PM
Joined: Mar 2001
Posts: 333
S
Member
Disregard this post..... [Linked Image]

Essex Electric Company(cable manufacturer)
lists their 10/2 w/grnd as having the approximate dimensions of .22"x.49". Per Chapter 9, 1" EMT @40% fill is only good for .346", so 1¼" EMT would be needed. For RNC sch40, 1" is .333", so 1¼" RNC would also be needed. ½" EMT @ 40% fill is good for .122". Essex lists their 14/2 w/grnd as having the dimensions of .17"x.37", so even the 14/2 would need to be in 1¼".


steve

[This message has been edited by stamcon (edited 03-31-2005).]


Steve
#50297 03/30/05 11:25 PM
Joined: Jun 2003
Posts: 681
P
Member
10/2 NM installed in 1/2 conduit.... I think not! [Linked Image]

Read the last sentence of Note (9) in Chapter 9.

Pierre


Pierre Belarge
#50298 03/31/05 01:09 AM
Joined: Sep 2003
Posts: 650
W
Member
Stamcon,

Don't confuse diameter with area. The 10/2 has a cross section of 0.49x0.22, and thus an area of about 0.085 _square inches_. However code requires us to treat it as a circular object with a diameter of 0.49", or a 'code calculated area' of 0.189 square inches.

For a _single_ conductor or cable, you are allowed to go to 53% fill, so 3/4 EMT would be sufficient for this particular 10/2.

Note that if this is conduit in a wet location, you need wet rated conductors. NM-B is _not_ rated for wet location use. Also pulling individual THHN/THWN conductors is probably much easier [Linked Image]

-Jon

#50299 03/31/05 01:21 AM
Joined: Mar 2001
Posts: 333
S
Member
Jon, my WAY bad. Thanks for the correction.

[Linked Image] steve [Linked Image]


Steve
#50300 03/31/05 01:59 AM
Joined: Jul 2004
Posts: 9,772
Likes: 14
G
Member
Then I do this type of thing I cheat. Find a single conductor about the same diameter as the flat side of the cable and use the table for that conductor.


Greg Fretwell
#50301 03/31/05 10:12 PM
Joined: Aug 2004
Posts: 34
H
Member
When you stated that you would need a weatherproof cover I'm thinking this would be located outside in which would be concidered a damp of wet location. Romex is not listed for these locations 334.12(B)(4)

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