314.16 (B) (2) Clamp Fill 2008

[Daniel Palmquist]

I was reading at http://ecmweb.com/nec/code-basics/electric_box_fill_calculations/ about 1/4 of the way down the page it says on
2. Cable clamp volume One or more internal cable clamps count as a single conductor volume, based on the largest conductor that enters the box. Cable connectors that have their clamping mechanism outside the box aren't counted.
Am I to gather from this that it is counted when the cable clamp or mc/romex type connector is facing inwards (inside the box)? I have never seen this and it really doesn't make sense due to an article I believe stating that fittings or their lock-rings are not counted.

Here is another question that may seem stupid but I need to know because I'm taking the Clark County Journeyman Exam this coming Friday: Are Wire-nuts counted in derating or any calculation for resistance or fill? I was on a website http://electriciansexam.com/ and it gave a so called short test that I got to over question 100 and it was still going and some of the questions I know I was correct on stated was wrong. It was asking questions on conduit fill where I used Table 4 and 5 of Chapter 9 for different sized conductors I took the area2 added them up and used the percentage from Table 1 and then chose the proper conduit in Table 4 yet it was wrong. One of the questions on that website asked about a 'wire stretcher' so I realized that it was probably bs. Does anyone know anything about that? That is really messed up and I think the guy who made that website is a scam artist.

 

[ActionDave]

You may have never seen a box with internal clamps unless you have done some work in an old building. I haven't used one in a long time, and haven't bought one in even longer.

Back when you could fill up your tank for less than a days pay metal boxes had a clamps built into the box. Those are internal clamps and count toward box fill. The clamps that one can carry around in ones pocket are external clamps.

 

[Sierrasparky]

The cable clamps on the inside of NM boxes are also the ones needed to be counted.

 

[ActionDave]

Are the clamps not considered in the calculation given on the inside of the NM box? I have always gone by that.

 

[Dennis Alwon]

I believe we had a thread on this not to long ago. The manufacturers stated that the calculation in the box is there and the deductions for fill must be applied using the NEC- they do not account for the clamp, so we must deduct it in our calculations just like any other box.