Ampacity adjustment through drilled members?

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ritelec

ritelec

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Jersey
Hello.
I'm reading opinions about having to apply ampacity adjustment to conductors (cables) running through bored holes in lumber. Some say adjustments apply, some say as long as you can get the wire in with out damaging it your good to go.
I'm looking at inspector forums, this forum and other forums.

Is there a definitive yes or no answer on this.

I was asked to file for a permit on wiring that a previous home owner did throughout the basement (which also feeds first floor and exterior and ...)
That owner didn't pull any permits, and there was a foreclosure on the house.
For the sale of the house the new potential owners will need to get a permit and inspections on this wiring to get a CO.

I see some box fill problems, supporting, gfci etc. but for the most part, the guy (gal) did a clean job. My biggest concern is large bored holes with 20 or more nm cables running through them ( like across the ceiling going from one end to the other). Some holes also share coaxial and LV wire in them.


OK, another concern is all the splice boxes in the ceiling. He has home runs and switching, and multiple slice boxes through out up inside the floor joists. The floor to the bottom of the joists has to be about 6' 7". To me it looks like he was going to bury everything and put the boxes in the joist to get headed room. Maybe not ??? Maybe he did intend to leave it open, and just wanted them up inside so you wouldn't hit your head on them.

Thing is, how would an inspector see these boxes ??? But, first things first,
the bundled or not considered bundled nm wire.

I don't pull permits and have others do the work so I'm not sure if I will sign on for this.

If I did decide to, how might I attack the multiple wires through the ceiling joists. How would the inspector view these wires and if they should be derated (ampacity adjustified) or not considered bundled.

Thank you
 
There is no limit as to the number of NM cables through a bored hole in wood if that hole is not filled with fire or draft stop material. The question becomes are the cables considered bundled for the 14½" that they run in free air between the holes in the joists? IMO no, others will disagree. :giggle:
 
My understanding is inspectors here will consider them bundled within the joist bay as well as at the hole, triggering the 24" bundling rule. So this is definitely a check with your AHJ issue.

I've thought somebody should make a plastic ring with slots around the perimeter, so you could use one in each joist bay, with 1-3 cables in each slot. That would make it clear than cables in different slots aren't bundled together, because the ring would "maintain spacing".

Cheers, Wayne
 
I believe the op described a retroactive permit, where occupancy has been revoked from existing building.

In my area retroactive permits remove all finished walls, and demo any remodel equipment not planned with original structure, or permits. That could be several layers of renovation tampering over the years.

The stucco & sticks stand on their own when the lot gets gutted.
 
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Often I used to hear the maximum number of NM cables in a bored hole is 3, today there is no basis for that. Perhaps when we had NM, that was the max could get through a hole and still maintain the 1 1/4' set back.
If the cables are installed in insulation then that impacts the ampacity rating.
But ampacity is determined at the 90 C rating of the conductor so as long as the derated ampacity is not less than the 60 C rating there is no impact, So often for running thru a top plate there may be no impact.
So the answer is fairly definite...
 
ritelec said:
... My biggest concern is large bored holes with 20 or more nm cables running through them ( like across the ceiling going from one end to the other). Some holes also share coaxial and LV wire in them.
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Do all of the holes meet the building code requirements? A typical requirement is the hole diameter can be no larger than 1/3 of the depth of the joist, and it must be more than 2" away from the joist's top and bottom edges.
 
ritelec said:
Some holes also share coaxial and LV wire in them.

Thank you
Click to expand...
No NEC issue on that, NM is a chapter 3 wiring method, same as running coax along side MC or rigid. Now interference from power cables into coax and LV is possible but the NEC does not care about that.
 
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