Conduit fill 1/2 inch EMT

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tx2step

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North Texas, DFW area
I'm out of town and don't have a code book with me. I was just asked to see if the following THWN mix can be put into a 1/2 inch EMT to go to a residential rooftop condenser:
2 #8 + 1#10 + 2 #12 # 1 #14 THWN.

It looks overfilled to me, but without a code book I can't check for sure. Can one of you guys let me know?

The run length across the roof is fairly short. Being on the roof, it'll be a wet location.

The #8 &#12 are current carrying - what amp rating would they be good for?

this will teach me to leave town without my code book...

Thanks for for the help!
 
highlegdelta said:
Sounds like somebody trying to get answers for their homework

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LOL. If so, points for creativity.

The fill charts I was just looking at lists just 3 #8 in 1/2" EMT, so I'm pretty sure 2 #8 plus 4 other wires is overfilled, but you cant know if you're above 40% w/o calculating circular mils. If it is overfilled, the rest of the questions are moot.

4-6 CCC in a raceway is 80% per table 310.15(B). No idea of rooftop temp or termination temps (w/o that info, assume 75*C).

and I've never seen a residence with a condenser unit on the roof. Also, that #14 ground/neutral seems wrong for #12 ungrounded conductors.
 
JFletcher said:
LOL. If so, points for creativity.


I've never seen a residence with a condenser unit on the roof. Also, that #14 ground/neutral seems wrong for #12 ungrounded conductors.
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That's what made me think it is a book question. Weird combination of wires, weird circumstance and the #14 just so happens to be the straw that breaks the conduit fills back.

Also, he has another post asking an equally academic quesntion.
 
highlegdelta said:
Sounds like somebody trying to get answers for their homework

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Nope, just don't have my book with me. You can check my profile.

You can only put 3 #8 or 5 #10s in a half inch, so I'm pretty sure it's overfilled and pass inspection. I don't think you could pull it without skinning the insulation, anyway.
 
Well I stand corrected.

So since it appears to be real, why would you be pulling that combination of wires?
tx2step said:
Nope, just don't have my book with me. You can check my profile.

You can only put 3 #8 or 5 #10s in a half inch, so I'm pretty sure it's overfilled and pass inspection. I don't think you could pull it without skinning the insulation, anyway.
Click to expand...

highlegdelta said:
That's what made me think it is a book question. Weird combination of wires, weird circumstance and the #14 just so happens to be the straw that breaks the conduit fills back.

Also, he has another post asking an equally academic quesntion.
Click to expand...


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tx2step said:
Nope, just don't have my book with me. You can check my profile.
Click to expand...

You have 458 posts, I hardly think you are a student....... looking for answers.
I do wonder why the #14? Was it going to be a ground? For the # 12's? Even on a 15 amp breaker you could get challenged that if you are running the 12's for voltage drops you have to increase the ground too. So it would have to be 12. Just asking.
Plus you'll never get all that in 1/2 inch.... ;)
 
fmtjfw said:
Go to NFPA site. Look for list of all standards. Select NEC 70. There will be a link for on-line reading.
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I got that to work, but it's painfully slow here!

as I thought, that would be overfilled. .122 allowed at 40%, and .1306 worth of wire. Besides, it would pull so hard it would skin the wire. Don't know what he was thinking.

Thanks!
 
qcroanoke said:
You have 458 posts, I hardly think you are a student....... looking for answers.
I do wonder why the #14? Was it going to be a ground? For the # 12's? Even on a 15 amp breaker you could get challenged that if you are running the 12's for voltage drops you have to increase the ground too. So it would have to be 12. Just asking.
Plus you'll never get all that in 1/2 inch.... ;)
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Dont really know exactly what he's doing. He could use the EMT for the ground, but it still is better to just put it in a separate 1/2 & 3/4 and not worry about it.

Thanks!
 
tx2step said:
Nope, just don't have my book with me. You can check my profile.

You can only put 3 #8 or 5 #10s in a half inch, so I'm pretty sure it's overfilled and pass inspection. I don't think you could pull it without skinning the insulation, anyway.
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I did the math just for fun. It is overfilled but only by a little, .1306. Forty percent fill on half inch emt is .122.

Looking at the wire sizes it seems like someone was reducing the neutral on two MWBCs fighting for every square inch they could.
 
qcroanoke said:
You have 458 posts, I hardly think you are a student....... looking for answers.
I do wonder why the #14? Was it going to be a ground? For the # 12's? Even on a 15 amp breaker you could get challenged that if you are running the 12's for voltage drops you have to increase the ground too. So it would have to be 12. Just asking.
Plus you'll never get all that in 1/2 inch.... ;)
Click to expand...

I cant get hold of him to ask, but I assume the #12 was for a service plug by the condenser - I don't know what else it would likely be for. Probably plans to tie into an existing circuit for that.

Thanks!!!
 
ActionDave said:
I did the math just for fun. It is overfilled but only by a little, .1306. Forty percent fill on half inch emt is .122.

Looking at the wire sizes it seems like someone was reducing the neutral on two MWBCs fighting for every square inch they could.
Click to expand...

That could be it, but I don't think it's worth the effort. I'll tell him to split it up into 2 conduits and be done with it.

Thanks!
 
highlegdelta said:
That's what made me think it is a book question. Weird combination of wires, weird circumstance and the #14 just so happens to be the straw that breaks the conduit fills back.
Click to expand...

The #14 would have to be a neutral b/c the #10 would be the grounds for the dual 8s, and you only need one EGC in the conduit... unless the EMT is serving that role. but then why pull neutrals to eqpt that doesnt need it? especially when it blows your conduit fill???

"Short run" would tell me the 12s werent run for VD...

On a 15A circuit, can you run a #14 non-CCC neutral or ground if the ungrounded conductors are #12? I thought the answer was in 250.122....
 
Might be a mini split. The 2 #8 and #10 feed the CU and then the CU feeds the mini split AHU with the 2#12 back inside the building. The 14 would be the control wire from the CU to the AHU. Lots of these in my area, although we keep the control a #12, but it likely doesn't need to be.

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woodduder said:
Might be a mini split. The 2 #8 and #10 feed the CU and then the CU feeds the mini split AHU with the 2#12 back inside the building. The 14 would be the control wire from the CU to the AHU. Lots of these in my area, although we keep the control a #12, but it likely doesn't need to be.

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Ahhh. I've yet to install one of those.

EMT on a rooftop in FL, possible in direct sunlight too... I imagine the ambient could top 150+*, which would lead to some serious derating, which is why the #8 is in there in the first place, amiright?
 
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