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Old 01-26-2009, 06:52 PM   #16
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How many 12 AWG Runs in a piece of 2" sch. 80?


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Originally Posted by chris75 View Post
Because he is asking if its alright to do what he wants to do, IMO if no codes are in order, then why ask if its okay?
He wants to know if it'll catch on fire, not what he needs to do to follow code. The two often coincide but not always.

For example a 25 inch nipple isn't going to be more of a fire risk than a 24 inch nipple but under the code it changes the rules completely.

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Old 01-26-2009, 06:55 PM   #17
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How many 12 AWG Runs in a piece of 2" sch. 80?


How long is the conduit?
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Old 01-26-2009, 06:58 PM   #18
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How many 12 AWG Runs in a piece of 2" sch. 80?


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Originally Posted by Gigs View Post
He wants to know if it'll catch on fire, not what he needs to do to follow code. The two often coincide but not always.

For example a 25 inch nipple isn't going to be more of a fire risk than a 24 inch nipple but under the code it changes the rules completely.

So tell me this, how many cables is it before it does catch on fire?
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Old 01-26-2009, 06:59 PM   #19
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How many 12 AWG Runs in a piece of 2" sch. 80?


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Did you read my code section? 312.5 (C) does not agree with you at all.
No I did not. It seems Exc. (g) kills that idea.

I only looked at note 2 to ch. 9, table 1 before responding. Live and learn. With that said, figuring cables the way the NEC wants him too, he's gonna need two or three 2" pipes for that. Time to get out the KO punch.
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Old 01-26-2009, 07:17 PM   #20
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How many 12 AWG Runs in a piece of 2" sch. 80?


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So tell me this, how many cables is it before it does catch on fire?
That depends on a lot of things, but assuming he is using 20 amp breakers with his 12 gauge romex, I'd say he'd have a hard time putting too many in there.

From what he described it is just a sleeve after all.
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Old 01-26-2009, 07:20 PM   #21
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How many 12 AWG Runs in a piece of 2" sch. 80?


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With that said, figuring cables the way the NEC wants him too, he's gonna need two or three 2" pipes for that.
Even if he were following the NEC, you have to follow derating but not fill on sleeves. With small Romex the fill calculation is what gets you.
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Old 01-26-2009, 07:45 PM   #22
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How many 12 AWG Runs in a piece of 2" sch. 80?


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I am sure it isnt "as many as I can fit".
As many as you can comfortably fit.
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Old 01-26-2009, 08:33 PM   #23
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How many 12 AWG Runs in a piece of 2" sch. 80?


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How long is the conduit?
Maybe 5 feet long, and there is a 90 degree elbow at the end so the wires can more easily flow into the rafters.
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Old 01-26-2009, 08:39 PM   #24
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How many 12 AWG Runs in a piece of 2" sch. 80?


I give up, but do what you feel is right.
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Old 01-27-2009, 08:30 AM   #25
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How many 12 AWG Runs in a piece of 2" sch. 80?


Since it is longer than 24 inches derating applies. If you put more 9 current carrying conductors you need to derate the current carrying capacity.
But since don't follow the NEC as many as you can fit without damaging the cables.
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Old 01-27-2009, 11:51 AM   #26
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How many 12 AWG Runs in a piece of 2" sch. 80?


Question
If you were to drill holes in the sides every foot or so to ventilate the conduit, would that have any effect? I imagine NEC does not address something like that
Is derating due to just potential heat build up, or is it also the effect of current flowing on wires packed together?
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Old 01-27-2009, 12:06 PM   #27
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How many 12 AWG Runs in a piece of 2" sch. 80?


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Question
If you were to drill holes in the sides every foot or so to ventilate the conduit, would that have any effect? I imagine NEC does not address something like that
Don't do that.

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Originally Posted by Scuba_Dave View Post
Is derating due to just potential heat build up, or is it also the effect of current flowing on wires packed together?
Heat build up. Some heat is caused by the fields interacting and most by direct resistance.

Thing is, with 12 gauge wire the true ampacity is higher than 20 amps so you can derate it a good amount and still use it with 20 amps overcurrent protection.
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Old 01-27-2009, 02:33 PM   #28
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How many 12 AWG Runs in a piece of 2" sch. 80?


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Since it is longer than 24 inches derating applies. If you put more 9 current carrying conductors you need to derate the current carrying capacity.
But since don't follow the NEC as many as you can fit without damaging the cables.
So for 12-2 you would hit derating at the 5th cable
Curious how many total cables & still have 20a capacity?
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Old 01-27-2009, 03:26 PM   #29
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How many 12 AWG Runs in a piece of 2" sch. 80?


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So for 12-2 you would hit derating at the 5th cable
Curious how many total cables & still have 20a capacity?
4 12-2's equals 8 current carrying conductors

After 9 current carrying conductors, then they start taking a hit.... Check out table 310.15(B)(2)(a), If you still wanted 20 amp capacity you could increase wire size.

#10 AWG is good for 40 amps as far as derating goes. THis would get you into the 10-20 Current Carrying Conductors at 50% value.

Last edited by chris75; 01-27-2009 at 03:36 PM.
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Old 03-02-2009, 11:27 AM   #30
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How many 12 AWG Runs in a piece of 2" sch. 80?


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Can anyone tell me how many 12/2 runs I can put into a piece of 2 inch schedule 80?

Thanks!
I got twelve (12) and the last one was a royal PITA!

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