NM cable (romex) in EMT (conduit) allowed?

Reply

  #1  
Old 01-20-09, 12:01 PM
R
Member
Thread Starter
Join Date: Feb 2006
Posts: 88
Received 0 Votes on 0 Posts
NM cable (romex) in EMT (conduit) allowed?

Would like information on potentially adding receptacles to an unfinished basement. 1/2" EMT condiut would be run from existing lighting boxes to the new metal receptacle boxes. May NM cable (14-2 romex) be run thru this EMT, or must separate wires (THHN?) be pulled? Any explanation accompanying the answer would be appreciated.

Thanks and best regards
 
Sponsored Links
  #2  
Old 01-20-09, 12:22 PM
I
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,943
Received 43 Votes on 41 Posts
A single piece of NM-B cable may be pulled through conduit, but it is not considered to be good practice. Typically you would use THHN conductors.

The reason is because of conduit fill and flexibility. The cross-sectional area of three THHN conductors is must less than that of a romex cable with the added bulk of the outer jacket and inner paper wrappers. Code limits the conduit fill to 40% which is roughly either 10 individual conductors or one romex cable.

Furthermore, the individual conductors pull more easily through the conduit requiring less force to pull and therefore less chance of kinking or skinning the conductors.
 
  #3  
Old 01-20-09, 12:30 PM
M
Member
Join Date: Dec 2007
Location: OR
Posts: 71
Received 0 Votes on 0 Posts
You are allowed to pull NM cable through EMT indoors as long as you don't exceed the allowable fill. There has been some confusion on this issue for historical reasons, but it is definitely allowed as of the 2005 edition of the NEC. For elliptical Romex cable, the fill is calculated by considering the Romex to be a single conductor whose diameter is the major diameter of the ellipse.

Individual wires will be easier to pull, however. I don't see any reason to use Romex unless you happen to have a bunch of it left over from another job.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: