Conduit requirements

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Hamberg

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Anyone know the requirements (NEC chapter 3, I think) for when/where you must use conduit? Supplying a garage sub panel through basement (approx 65') and up into a 2 x 4 drywall cavity in the garage. (if it matters it's 2/3 NMB copper)
 

Hamberg

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Inside the wall conduit wouldn't be required if you use the properly sheathed cable.
Hey @Sparky617 - using non-metallic (NM-B) cable. Also, wasn't so much worried about "in the wall" as the run in the (FINISHED) basement.

I added a chase when I was finishing but there would literally be no way to add conduit with out ripping the ceiling out. (if it matters we are still in NEC 2014 in our area)
 

Sparky617

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So where would you be putting conduit? In the chase is your plan just to pull it through without stapling it? Not sure that is a problem, but you will want to make sure the cable won't be subject to damage from someone driving a screw or nail into the ceiling or wall and hitting the cable.
 

Hamberg

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So where would you be putting conduit? In the chase is your plan just to pull it through without stapling it? Not sure that is a problem, but you will want to make sure the cable won't be subject to damage from someone driving a screw or nail into the ceiling or wall and hitting the cable.
Comes from the garage into an unfinished utility area, into a finished section, then into the service panel area. No chance of anyone running a screw into the (PVC) chase and the cable will run under the floor joist in the unfinished sections.

My fear was (as I couldn't find any "required" reference in the NEC) that because of the cable size, I'd need to conduit under the floor joists. But, now that I think about it, I can't find a reference because it's not needed.
 

Sparky617

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Staple the NMC to the floor joists and you'll be good. I just did this and passed inspection for an 50 amp EV circuit to my garage and a new sub panel in my basement. I did have to put nailing plates in where it passed through a stud to protect it from drywall screws and nails.
 

Guzzle

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Says it's 90C but good for 100A. If your breakers are rated for 60/75C you're supposed to run it at the 60/75C current, 90A or 75A.

You need to be a bookkeeper to keep track of this.

Here's more about dry/wet locations.
 
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Guzzle

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I'm more sure-footed with voltage drop. Ampacity seems to have a lot of fine print to read.

For #2 AL, 65', 100A gives a 1.4% drop from 240v & 80A gives a 1.1% drop.
 

Hamberg

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Maybe @Sparky617 or @afjes_2016 could help out the rookie here?

How/why does the temperature rating of the cable, make a difference as it relates to the breaker?

In my feeble mind I look at the chart below and say I am using a #2 XHHW-2 aluminum cable, which according to the chart is good to 100A BUT there is no reference to the breaker which may be rated at a different degree (I'm guessing 75C is typical??)

I'm missing something here that ties them together...



1637935637198.png
 

Guzzle

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You left out the footnote for the two asterisks for #10 thru #18 in the leftmost column. Here's the footnote \/

**Refer to 240.4(D) for conductor overcurrent protection limitations.
 

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