Hi Julie,
Discussions pertaining to the ?length of free conductor? have been around for a number of years. Prior to 1999 edition, there was no mention of how to measure the 6 inches of free conductor. Proposals were submitted for; 1) starting the measurement at the point in the box where it emerges from its raceway or cable sheath, and 2) starting the measurement from the exterior edge of the box. While I couldn?t find the Report on Proposals (ROP) for the 1999 edition, I found similar wording submitted for the 2005 ROP . . . both were rejected. The 2005 ROP can be found on the NEC Digest website.
http://www.nfpa.org/itemDetail.asp?...C%AE%20Resources/ROPs%20and%20ROCs/2005%20ROP
Report on Proposals ? May 2004 NFPA 70
3-74 Log #2287 NEC-P03
(300-14)
Recommendation:
Revise text as follows:
Where the opening to an outlet, junction, or switch point is less than 200 mm (8 in.) in any dimension, each conductor shall be long enough to extend at least (75 mm (3 in.)) (5 in.) outside the opening.
Substantiation:
Three inches of conductor to install a device is not enough. It allows almost no play or room for error. If the conductors need to be trimmed back in the future, there is not enough conductor to do it.
Panel Meeting Action: Reject
Panel Statement:
A Task Group consisting of Panel 9 members (having jurisdiction over Article 314) and Panel 3 (having jurisdiction over Article 300) studied and reviewed the issues raised by proposals in both the 1996 and the 1999 Code process, and determined the present text in 300.14. Where boxes or plaster rings had openings that were smaller than 8 inches in any dimension, a 6 inch conductor may not have sufficient length to project more than a few inches outside the box or ring, depending upon where the conductors actually entered the box. It was decided that the conductors entering into the box must be at least 6 inches long measured from the point in the box where the conductor emerges from the raceway or cable sheath and then have at least 3 inches outside the opening. This would permit easy splicing of the conductors within the box or connection to most devices without unduly overfilling the box. Adding an additional 2 inches may overfill the enclosure. Adequate substantiation has not been provided for justifying this additional length.
Number Eligible to Vote: 12
Ballot Results: Affirmative: 12
3-75 Log #2336 NEC-P03
(300-14)
Final Action: Reject
Recommendation:
Revise text as follows:
Length of Free Conductors at Outlets, Junctions, and Switch Points. At least 150 mm (6 in.) of free conductor, measured from the exterior edge of box, shall be left at each outlet, junction, and switch point for splices or the connection of luminaires (fixtures) or devices. Where the opening to an outlet, junction, or switch point is less than 200 mm (8 in.) in any dimension, each conductor shall be long enough to extend at least 150 mm (6 in.) outside the opening.
Substantiation:
NEC 300.14 Length of Free Conductors at Outlets, Junctions, and Switch Points states: "At least 150 mm (6 in.) of free conductor, measured from the point in the box where it emerges from its raceway or cable sheath, shall be left at each outlet... "The problem with this code statement is that (6 in.) of free conductor should be measured from the exterior of the box instead of the "point in the box where it emerges from its raceway or cable sheath". This in turn, would change "at least 75 mm (3 in.) outside the opening" to at least 150 mm (6 in.) outside the opening. The primary reason for changing the article's point of measurement is in regards to safety. Measuring from the point in the box from the raceway or cable sheath actually shortens the total overall length of free conductor that extends beyond the box. The shortened length of conductor makes it difficult to work on a device safely when that device is serviced or exchanged. It is possible to damage the conductor on the edge or side of the box while trying to access the termination points on a device, such as a receptacle. The bare conductor and metal box could cause an overcurrent condition, resulting in a potential fire hazard. Another problem with the shortened conductor length is in regards to replacing a receptacle that can not be de-energized. Such a situation may occur in a hospital or industrial application. This could be a potential electrical shock hazard to the individual servicing the device.
Solution to the Problem: The safest solution to the problem would be to change the point at which the conductor length is measured from. The measurement for the (6 in.) free conductor length should be measured from the exterior (outer) edge of the box, rather than the raceway or cable sheath within the box. Measuring from the exterior edge would give a better working clearance away from the box, making it less likely to damage the conductor and would also make it easier to manipulate an energized device. A greater working clearance would then be safer without question.
Panel Meeting Action: Reject
Panel Statement:
See the first paragraph in the Panel Statement in Proposal 3-74.
Adding an additional 6 inches will most likely overfill the enclosure. Adequate substantiation has not been provided for justifying this additional length.
Number Eligible to Vote: 12
Ballot Results Affirmative: 12
Sometimes by reading statements from panels, it is easier to understand the Code.
Charles
