NM Cables in pipe sleeve into breaker panel

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richwaskowitz

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Location
Shelby Twp. MI, near Detroit
I am looking at a statement in a book by Ray Mullin on residential wiring where hr makes a statement without offering any specific article to back it up and I want to know if it is true and what the Code reference would be.

He shows a bunch of NM branch circuit cables entering a breaker panel from an unfinished basement ceiling down through a conduit sleeve (with a bushing on the end of it and all cables are secured within 12 inches of the entry point as required) and states that the pipe must be at least 18 inches long and not more than 10 feet. Why 18 inches?

Part two, what about the guy who stuffs a bunch of NMs into a 2 inch cable clamp? I'm pretty sure not too many inspectors would allow that (unless somebody's 2 inch connector is listed for that......

I am more interested in the sleeve question than the 2 inch connector question. I would have thought I could find it in 334.15 or 334.30
 
jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
The 2' connector with multiple small NMs is a no-no unless listed as you said.

From link below:
Cable clamps or cable connectors must be used with only one cable, unless that clamp or fitting is identified for more than one cable. Some Type NM cable clamps are listed for two Type NM cables within a single fitting (UL White Book, product category PXJV).
Click to expand...

For the conduit sleeve and 18", see 312.5(C) Exception. Why more than 18" and less than 10', IDK.

View attachment 15971

http://ecmweb.com/qampa/stumped-code-2
 
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infinity

infinity

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Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Took a little work but here it is from the 1999 ROP, seems like the 18" length is completely arbitrary:

(Log #3203)
9- 75 - (373-5(c), FPN, Exception-(New) ) Accept in Principle
Note: It was the Acton of the Technical Correlating Committee
that further considerations be given to the comments expressed on
the voting This action will be considered by the Panel as a
Pubic Comment
SUBMITTER Frederic P Hartwell, Mass Electrical Code Advisory
Committee
RECOMMENDATION Add an exception and Fine Print Note as
follows:
Exception: Cables with entirely nonmetallic sheaths shall be
permitted to enter a surface-mounted enclosure through one or
more non-flexible raceways not less than 18 inches (457 mm) in
length, provided all the following conditions are met.
a. The cables are fastened within 12 in (305 mm), measured
along the sheath, of the end of the raceway
b The raceway does not penetrate a structural ceiling or floor
c. A fitting ts provided on the end of the raceway to protect the
cables from abrasion and this fitting remains accessible after
installation
d. The raceway is plugged so as to prevent access to the interior
of the enclosure
e. Where installed in 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
(FPN) See Table 1 m Chapter 9, including Note 9 thereto, for
allowable cable fill in circular raceways. See Article 310 Note
8(a) of the Notes to Ampacity Tables of 0 to 2000 volts for
required ampacity reductions for multiple cables installed in a
common raceway
SUBSTANTIATION This is the perfected version of a NEC
proposal that failed by one vote entering the 1996 NEC. The
decisive negative vote concerned access to the interior of the
enclosure, which is addressed in this version It provides safe and
consistent installation requirements for the common,
workmanlike practice of using raceway sleeves for nonmetallic
sheathed cables entering panelboards and the like
PANEL ACTION Accept in Principle
I Revise "d" of the proposed exception as follows "d The
raceway is fastened at its outer end and plugged, using approved
means, so as to prevent access to the interior of the enclosure"
PANEL STATEMENT The panel wants to assure that the
raceway is secure
NUMBER OF PANEL MEMBERS ELIGIBLE TO VOTE 10
VOTE ON PANEL ACTION
AFFIRMATIVE 9
NEGATIVE 1
Click to expand...
 
jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
Nice work Rob. Thanks.

Edit: I noticed the 10' max for length was missing from that ROP, so I checked: it was added in the 1999 ROC.

Substantiation:

A 10 ft length limitation is suggested to prevent abuse of unlimited length, and which should be adequate for surface-mounted installations on walls of
basements, garages, rooms, etc. and permit an enclosure height where the raceway can extend into an attic or open joist space even with a 90 degree
bend at the top or bottom.
 
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jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
infinity said:
Took a little work but here it is from the 1999 ROP, seems like the 18" length is completely arbitrary:
Click to expand...

It really basically is IMO or least a CYA for the CMP.

From the 1999 ROP info you posted I looked up the 1996 ROP mentioned.

This is it:

Add an 18-inch minimum raceway length.
This is to address the concerns in Proposal 9-68, and 9-73.
The distance chosen is long enough to provide reasonable containment of the enclosed cables without
specifying a length so long as to require mandatory derating of the cables, that would largely defeat its purpose and applicability.
 
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