3- 14-2 romex in draft stopped hole then run down stud stapled and wire tied (2 wires under staple 3rd wire wire tied

[klineelectric]

I am a licensed electrical contractor 25 yrs in buisiness. I have an inspector who is telling me that when I have 3 wires together immediately after exiting fire stopped hole that i have to derate the wire again(compounding the deration) of where i came through the hole. So 334.80 says I derate the wires in the hole, I have 6 # 14 conductors (3 -14-2 romex) so going to 310.15(c)(1) 4-6 conductors gets derated to 80%
now going from 90% column of 310.16 ................ 14awg is rated 25 amps
so derating the wires in the hole would be ......... 25amps X .8= 20 amps (wire is rated for 20 amps after derating, going on a 15 amp breaker)
Now he says since the 3 wires in the hole are stacked together immediately after exiting hole for longer than 24" I have to further derate from the derated ampacity from the hole. So i guess he thinks i dont follow what the code says and derate the sections in question on their own. That I would instead derate the hole and take that number to further derate for the wires stapled down the stud to the switch. (2 wires under staple 3rd wire wire tied to other two)
So he is saying ................................................................................Hole derated to 20 amps
derate 3 wires together from already derated wire 20amps x .8=16 amps (while this is still over the 15 amps that is not the point, if one of those wires was a 3 wire and I had to go to 7-9 conductors @70% I would be over) Yes I know I can use stackers but not the point because where does it end. Selection of ampacity 310.14(a)(2) says there can be more than one ampacity for a given length of wire and you use the lowest. Please tell me if I am wrong. BTW the code handbook has a perfect example of 4 12- 2 romex without airspace and their conclusion says you can have romex wires (no more than 9 conductors) without airspace in almost all circumstances without having to upsize the wire due to derating. My understanding is you derate the hole... 25 amps X .8 %=20amps
Then you derate the 3 wires together ..........25 amps X .8%=20amps

 

[infinity]

You only need to derate once in your scenario. So 6 CCC's = 80% as you've stated.

When you have a minute please update your location and occupation in your profile.
Thanks.

 

[klineelectric]

You only need to derate once in your scenario. So 6 CCC's = 80% as you've stated.

When you have a minute please update your location and occupation in your profile.

is there anything Im missing in the code to point him too

 

[Dennis Alwon]

is there anything Im missing in the code to point him too

Ask him to read this forum. If you look at it logically there is no reason to make a double de-rate. The de-ration for the hole is satisfied and then the de-ration for the bundle is de-rated. They are both satisfied.

 

[klineelectric]

I was thinking about forwarding this forum to him.

Ask him to read this forum. If you look at it logically there is no reason to make a double de-rate. The de-ration for the hole is satisfied and then the de-ration for the bundle is de-rated. They are both satisfied.

maybe if some more people respond and help make the point I will

 

[infinity]

maybe if some more people respond and help make the point I will

Ask what code section specifically requires you to apply a "double" derating in this installation. Also if you apply some logic you would see that once you've derated for the hole the conductors are already adequate for the bundling.

 

[LarryFine]

He's nuts wrong. A few more holes and the wire would have no ampacity at all.

 

[tom baker]

The answers above are correct so we won’t likely see more answers

 

[klineelectric]

He's nuts wrong. A few more holes and the wire would have no ampacity at all.

I said something to that effect to him as I was trying to wrap my head around compounding the deratings. Im waiting for an answer from his supervisor, Been waiting a week.

 

[klineelectric]

The answers above are correct so we won’t likely see more answers

Thank you Tom, I guess i was hoping there was something I missed that would help. You would think the( selection of ampacity 310.14 (a)(2) where more than one ampacity applies for a given circuit length, the lowest ampacity value must be used for the circuit) would be enough. Hopefully If a bunch my respected electrical peers chime in, it could make a difference

 

[Dennis Alwon]

So he turned you down even though a double de-rate would still be good for 15 amps?

 

[klineelectric]

So he turned you down even though a double de-rate would still be good for 15 amps?

He said it’s out of his hands (waiting for supervisor to clarify) to be honest I didn’t even do the double deration until posting this. I want this clarified so I don’t run into it where there are 7-9 conductors b/c then double de rating causes trouble

 

[Fred B]

But even with the De-rating from the 90deg C, your Romex cannot be sized for greater than the 60deg C column. If your de-rating takes it lower than your 60 deg rating then you must upsize.
If the inspector is trying to de-rate the 60deg wire he's going to have significate trouble ever using #14, but he also would be dead wrong.
Refer him to 334.80 for guidance.

 

[klineelectric]

My builder just heard from head building official ( who is a master electrician ) and he said to only derate once in this instance, and I was good to go. My re-inspection is tomorrow.

 

[infinity]

My builder just heard from head building official ( who is a master electrician ) and he said to only derate once in this instance, and I was good to go. My re-inspection is tomorrow.

I'm glad that you stuck to your guns. Inspector mistakes need to be called out so that they're not repeated over and over again.