Number of cables through a hole

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sfav8r

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A friend is doing a kitchen remodel and has called me for information along the way. He just called for the inspection and failed due to "too many wires going through a single hole." and "Using a switch box as a junction box." First, for the second fail since I think its easy. The "switch box" the inspector is referring to is a 2 gang WP box (mulberry). He claims that is not a "junction box" that it is made for putting switches in and can't be used as a junction box. I have no idea what that's all about. However, the 2nd issue is that there are a number of cables (12/2, 14/2, 12.3 romex) exiting the box out a single 1" hole in the back of the box. The situation is that the box is fed with THHN via conduit and then spliced with Romex that runs out the back of the box and into the wall. He cited 310.15(b)(2)(a) stating that with that number of conductors they would have to be derated. I don't believe this is the case because the length is only an inch or two. I believe the 24" rule would apply and no derating is necessary. Having said that, I do believe he could have called the fact that the 1" clamp is almost certainly not rated for that number of conductors. I suppose the clamp could be removed and a busing installed instead and the romex could be stapled as it enters the house. Any thoughts?
 
Not sure what a mulberry is
For the cables going into the back of the box, each individual run of NM-B needs to be secured within 12" or 8" if no clamps. if a hole was drilled in the back of the box then that may be an issue as well
 
A clamp is required. The exception that allows boxes without clamps is only for single gang NM boxes. De-rating would not be an issue but as you suggested the clamp is not going to be listed for the multiple odd combination of cables.

With multiple cables being spliced you are probably going to be close if not overfilled. You would be better off using a 664 3R can and drilling multiple holes for cable clamps in the back.
 
Did you look at the table? The most you have is 7 current carrying conductor's and with that you have a 70% derating to do. Look at NM Cable-- even though it is rated 60C we can still derate from the 90C column because 334.112 states nm is rated 90C.

At 90C 12awg is rated 30 amps. Multiply by 70% and we still have 21 amps so we can use a 20 amp breaker on it. Same is true for the 14 awg.

Now 12/2 and 12/3 plus a 14/3 using the same connector is probably an issue. It also sounds like fill may be an issue. What size (cu.in ) is the box?
 
sfav8r said:
A friend is doing a kitchen remodel and has called me for information along the way. He just called for the inspection and failed due to "too many wires going through a single hole." and "Using a switch box as a junction box." First, for the second fail since I think its easy. The "switch box" the inspector is referring to is a 2 gang WP box (mulberry). He claims that is not a "junction box" that it is made for putting switches in and can't be used as a junction box. I have no idea what that's all about. However, the 2nd issue is that there are a number of cables (12/2, 14/2, 12.3 romex) exiting the box out a single 1" hole in the back of the box. The situation is that the box is fed with THHN via conduit and then spliced with Romex that runs out the back of the box and into the wall. He cited 310.15(b)(2)(a) stating that with that number of conductors they would have to be derated. I don't believe this is the case because the length is only an inch or two. I believe the 24" rule would apply and no derating is necessary. Having said that, I do believe he could have called the fact that the 1" clamp is almost certainly not rated for that number of conductors. I suppose the clamp could be removed and a busing installed instead and the romex could be stapled as it enters the house. Any thoughts?
Click to expand...

The cables need to enter the box in an approved connector(s) with the number of cables within the connector used per its listing. The 2 gang weatherproof FS box is fine for a splice box if it's sized properly.
 
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