Nonmetalic sheathed cable

[xunomemo]

I have a code check sheet that sites two regulations for securing NM when not clamped to box with an approved clamp. What is the difference between 1999 NEC 370-17cX and 1999 NEC 336-18 for securing NM when not clamped to box? I would appreciate what ever clarification anyone could proveide.

 

[websparky]

Re: Nonmetalic sheathed cable

NEC 1999 370.17 (C)......Where nonmetallic-sheathed cable is used, the cable assembly, including the sheath, shall extend into the box no less than ? in. (6.35 mm) through a nonmetallic-sheathed cable knockout opening. In all instances, all permitted wiring methods shall be secured to the boxes.

In this article above, the subject is "boxes" and basically says that you can't just drill a hole in a plastic box and stick in the cable. They want to be sure you use a manufactured hole that has the plastic clip that holds the cable.

NEC 1999 336-18. Supports .....Cable shall be secured in place at intervals not exceeding 4? ft (1.37 m) and within 12 in. (305 mm) from every cabinet, box, or fitting.

In this article above, the subject is about "supporting" of the cable as it is installed and when it enters anything. The cable needs to be supported within 12" any entry.

Dave

 

[david]

Re: Nonmetalic sheathed cable

I think the key to what you are asking is the approved clamp. The general rule in both these sections require NM cable to be secured to the box.

quoted in part:
In 336-18 ?Exception No. 2: A wiring device identified for the use, without a separate outlet box, incorporating an integral cable clamp shall be permitted?

Some boxes use a wiring device that is factory designed to secure the NM cable to the box and their would be no need to use an approved cable clamp.

370-17(c) Nonmetallic Boxes.
Exception: Where nonmetallic-sheathed cable or underground feeder and branch-circuit cable is used with single gang boxes no larger than a nominal size 2? in. x 4 in., mounted in walls or ceilings, and where the cable is fastened within 8 in. (203 mm) of the box measured along the sheath and where the sheath extends through a cable knockout no less than ? in. (6.35 mm), securing the cable to the box shall not be required. Multiple cable entries shall be permitted in a single cable knockout opening.

In this exception there is no need to secure the NM to a single gang nonmetallic device box( by an approved clamp or an factory wiring device) but notice the cable needs to be secured within 8 in. of the box verses the normal 12 in.

Though this is not part of your thread if you are wiring in an agricultural building the cable needs to be secured with in 8 in. of the box even when you use an approved cable clamp.

 

[michael nye]

Re: Nonmetalic sheathed cable

Just wanted to add to the question, how about a serfice panel, flush mount. If the romex is stapled within 12" of the panel can you just use a plastic snap on bushing? Or would a two screw connector be required, or the stablock type connectors?

 

[romeo]

Re: Nonmetalic sheathed cable

I wanted to post a question but not sure how to.

I hope I can get some response to this code artical 334.30 requiring nmc to be secured ( not supported )I believe that it applies to concealed work ( new homes ) so it is not permitted to lay nmc on strapping in open bays or to run across ceiling members and the strapping ( cross country )

Romeo

 

[romeo]

Re: Nonmetalic sheathed cable

I wanted to post a question but not sure how to.

I hope I can get some response to this code artical 334.30 requiring nmc to be secured ( not supported )I believe that it applies to concealed work ( new homes ) so it is not permitted to lay nmc on strapping in open bays or to run across ceiling members and the strapping ( cross country )

Romeo

 

[david]

Re: Nonmetalic sheathed cable

Romeo

334.30 Is requiring NM cable to be supported and secured. There are times for instances that stables will support and secure the cable. Most of the time the support is given from the framing member that the cable is secured to.

There are exceptions to the support requirements:

(B) Unsupported Cables. Nonmetallic-sheathed cable shall be permitted to be unsupported where the cable:
(1) Is fished between access points, where concealed in finished buildings or finished panels for prefabricated buildings and supporting is impracticable
(2) Is not more than 1.4 m (41/2 ft) from the last point of support for connections within an accessible ceiling to luminaire(s) [lighting fixture(s)] or equipment

 

[david]

Re: Nonmetalic sheathed cable

michael nye

you must use a approved cable clamp to secure NM cable to surface mounted panels.