# 2 Romex through 1 joist/stud hole?



## 3xdad

IMO, the splices are worse than the two cables in a single hole.

They may be interpreting 334.80(2011) wrong.


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## cad99

It is normal here in nd to run two nm's in same hole I drill all my home runs at 3/4" and never heard a complaint but we also have some weird stuff that is not in the nec that inspectors make us do.like tieing up troffers in the grid with painted grid wires.some inspectors really pull the card of being the ahj and demand you do everything there way.


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## macmikeman

cad99 said:


> It is normal here in nd to run two nm's in same hole I drill all my home runs at 3/4" and never heard a complaint but we also have some weird stuff that is not in the nec that inspectors make us do.like tieing up troffers in the grid with painted grid wires.some inspectors really pull the card of being the ahj and demand you do everything there way.
> 
> 
> Sent from my iPhone using Tapatalk


I routinely run 5 or six thru holes drilled in joist. Then I fan out the cables between the joists. Your local inspectors are little generals who need to be tied up and spanked by a german woman.


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## Dennis Alwon

If the hole is going to be fire caulked then you are subject to derating. Since the wire in nm is rated 90C then you can have 9 current carrying conductor's before the derating affects you. Generally speaking you can have 4 nm canles thru one hole without it affecting the ampacity of the nm. 

For instance #12 is rated 90C so it is good for 30 amps. Derate 8 current carrying conductor's is 70% so 30 * .7 = 21 amps-- still good.


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## chicken steve

Iirc, all the spray foam insulation spawned the _'rule of 9' _as applied to _'romex in hole'_ , which seem to forgo the usual 24" rule

~CS~


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## Ultrafault

They will cry foul if you undersize the neutral as well.


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## Bootss

have them show you in the code or a local ordinance in writing


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## AK_sparky

1 NM per hole? Does the inspector have stock in the local auger bit factory?


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## Dennis Alwon

arminkeller said:


> 1 NM per hole? Does the inspector have stock in the local auger bit factory?


I can imagine what the top plate above a panel would look like. Yikes-- you couldn't get enough holes in it for 20 circuits. Build a double wall with space between and there you go. One big hole.....:thumbup:


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## Ultrafault

Dennis Alwon said:


> I can imagine what the top plate above a panel would look like. Yikes-- you couldn't get enough holes in it for 20 circuits. Build a double wall with space between and there you go. One big hole.....:thumbup:


Simple economics will let you know what it looks like. More cost per wire means less wires. St. louis county houses are all code min.
20 circuits would be alot. 

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## backstay

TLinSTL said:


> Is this prohibited anywhere in the NEC? I cannot find anywhere that makes it not allowed, but all of the inspectors around here (multiple jurisdictions)will not allow it. I've been going along with it, drilling a hole for every NM wire. What finally put me over the edge was for a house I personally bought in which a city inspector said I had to redo, in the basement, where 2 existing NM wires went through 1 hole in the floor joists. This is in multiple spots and will require a few splices. The inspectors can't give me a code reference or any other justification other than that's just the way it is.


Time to educate the inspectors on their job. It's to "INSPECT" not make up rules.


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## Bootss

Dennis Alwon said:


> I can imagine what the top plate above a panel would look like. Yikes-- you couldn't get enough holes in it for 20 circuits. Build a double wall with space between and there you go. One big hole.....:thumbup:


I usually build" pop out " in the wall if its in the garageDennis


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## Dennis Alwon

Lep said:


> I usually build" pop out " in the wall if its in the garageDennis


We try and get them to do that also


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## Awseay

We have a city that only allows one nm cable per connector. No matter what size connector. From my experience it's pretty standard to drill 7/8-1" holes and do 2-4 wires. All you can do is obey the inspector and vent about it on here. That's what I do and it helps a little bit.


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## Semi-Ret Electrician

arminkeller said:


> 1 NM per hole? Does the inspector have stock in the local auger bit factory?


Not only that..what does the structural inspector say:laughing:


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## chicken steve

on those tgi's and gluelams.....

~CS~


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## Dennis Alwon

The more you allow the inspectors to make up rules the more they will do so. Think of it as an education. If you train yourself so you know what you are talking about you will get a lot of respect and they will usually listen. One wire per hole is absolutely ridiculous.


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## macmikeman

Dennis Alwon said:


> The more you allow the inspectors to make up rules the more they will do so. Think of it as an education. If you train yourself so you know what you are talking about you will get a lot of respect and they will usually listen. One wire per hole is absolutely ridiculous.


So is two, and so is three and deep down you know yourself from your own experience that ten or twelve cables thru a 2'' hole never ever ever was a real problem. 

Watch the new film coming out in 2017- Code Making Panels gone wild!


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## Dennis Alwon

macmikeman said:


> So is two, and so is three and deep down you know yourself from your own experience that ten or twelve cables thru a 2'' hole never ever ever was a real problem.
> 
> Watch the new film coming out in 2017- Code Making Panels gone wild!


For sure. I used to drill a 2 1/8" hole and bring down as many cables that would fit in there enroute to the panel. Never an issue. It has gotten ridiculous


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## Speedy Petey

Dennis Alwon said:


> If the hole is going to be fire caulked then you are subject to derating. Since the wire in nm is rated 90C then you can have 9 current carrying conductor's before the derating affects you. Generally speaking you can have 4 nm canles thru one hole without it affecting the ampacity of the nm.
> 
> For instance #12 is rated 90C so it is good for 30 amps. Derate 8 current carrying conductor's is 70% so 30 * .7 = 21 amps-- still good.


THIS! Explain this to them and see what they say. 

They CANNOT simply make up stuff and force you to do it (which is exactly what they are doing). That is not interpretation, it is totalitarianism.


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## Stash

Dennis Alwon said:


> The more you allow the inspectors to make up rules the more they will do so. Think of it as an education. If you train yourself so you know what you are talking about you will get a lot of respect and they will usually listen. One wire per hole is absolutely ridiculous.


This..

I've had inspectors come out and try to make up cosea on the spot (why I don't know) I usually carry the NEC with me, call them out and then don't have anymore problems with future inspections. 

I've also called their bosses if they really don't want to follow the code.


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## Achilles

Dennis Alwon said:


> If the hole is going to be fire caulked then you are subject to derating. Since the wire in nm is rated 90C then you can have 9 current carrying conductor's before the derating affects you. Generally speaking you can have 4 nm canles thru one hole without it affecting the ampacity of the nm.
> 
> For instance #12 is rated 90C so it is good for 30 amps. Derate 8 current carrying conductor's is 70% so 30 * .7 = 21 amps-- still good.


Before you tell your inspector this I would drop the 90°C part. (too many problems due to lugs & equipment downstream need to be rated 90°C)

Either way 25*.7 = 17.5 = 20A (next common breaker size)


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## Dennis Alwon

Achilles said:


> Before you tell your inspector this I would drop the 90°C part. (too many problems due to lugs & equipment downstream need to be rated 90°C)
> 
> Either way 25*.7 = 17.5 = 20A (next common breaker size)


There is no issue with the 90C part. The 90C column is there for a reason and that reason is for de-rating. You cannot use the 90C as the final overcurrent protective device but you certainly can use it to de-rate. 

Our inspectors know this info and if they don't I have no problem showing it to them.


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## Dennis Alwon

Here is the article to cite--



> 310.15(B) Tables. Ampacities for conductors rated 0 to 2000 volts
> shall be as specified in the Allowable Ampacity Table
> 310.15(B)(16) through Table 310.15(B)(19), and Ampacity
> Table 310.15(B)(20) and Table 310.15(B)(21) as modified by
> 310.15(B)(1) through (B)(7).
> *The temperature correction and adjustment factors shall
> be permitted to be applied to the ampacity for the temperature
> rating of the conductor, if the corrected and adjusted
> ampacity does not exceed the ampacity for the temperature
> rating of the termination in accordance with the provisions
> of 110.14(C).*


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## Achilles

Dennis Alwon said:


> There is no issue with the 90C part. The 90C column is there for a reason and that reason is for de-rating. You cannot use the 90C as the final overcurrent protective device but you certainly can use it to de-rate.
> 
> Our inspectors know this info and if they don't I have no problem showing it to them.


!!!Mind Blown!!!

I never considered 90°C for de-ration. Only tried to use it for feeder circuit ampacity. Thank you


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## Dennis Alwon

Since most terminations are 75C we cannot use the 90C column for our overcurrent protective device but we can use it for de-rating as long as the final ampacity is not greater than the 75C column-- assuming 75C terminations


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## Achilles

Dennis Alwon said:


> Here is the article to cite--


Now I've gone way off subject but

if the corrected and adjusted
ampacity does not exceed the ampacity for the temperature
rating of the termination

This is the part that I thought sends me back to 75°C


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## Dennis Alwon

Achilles said:


> Now I've gone way off subject but
> 
> if the corrected and adjusted
> ampacity does not exceed the ampacity for the temperature
> rating of the termination
> 
> This is the part that I thought sends me back to 75°C


Yes it does but only for the final overcurrent protective device as I stated above. You can still de-rate from the 90. 

Lets say you have a #6 thhn-- we see in the 90C column that it is rated 75 amps. Now we know we cannot use the wire at 75 amps but we can de-rate-from the 90C column. Say we have 8 current carrying conductor in a conduit that would be 70% * 75amps = 52 amps. We can only use a 50 amp breaker or a 55 amp breaker as long as the load is not greater than 52 amps. 


We do *not* need to start the de-rating from 65 amps which is the 75C column


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## Achilles

I understand. My first thought was all the RTU's I've run in separate conduits de-rating from 75°C.

makes me sad - happy going forward though


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## FF301

2014 code you need to derate if nm is running incontact with thermal insulation so to aviod derating, no more then 2 nm cables in a hole


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## Speedy Petey

FF301 said:


> 2014 code you need to derate if nm is running incontact with thermal insulation so to aviod derating, no more then 2 nm cables in a hole


The point being made is that even if you have to derate #14-#10 you can still have up to 8 CCC's since we derate from the 90 deg C column, and those conductors don't drop under their "typical" amperage until you have 9 or more CCC's.


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## Dennis Alwon

FF301 said:


> 2014 code you need to derate if nm is running incontact with thermal insulation so to aviod derating, no more then 2 nm cables in a hole


As stated above by both myself and Pete this info is incorrect. Try reading the posts I wrote just above yours. It also works for 14-10 as Pete pointed out. In fact I think it works for almost all conductor sizes- at least the smaller sizes


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## Dennis Alwon

Since NM must be used at 60C anyway then the derating from 90C, which is the actual temperature rating of the wire, does not hurt the conductor as long as the overcurrent protective device is not larger than the 60C rating after de-rating


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## EJPHI

Dennis Alwon said:


> Yes it does but only for the final overcurrent protective device as I stated above. You can still de-rate from the 90.
> 
> Lets say you have a #6 thhn-- we see in the 90C column that it is rated 75 amps. Now we know we cannot use the wire at 75 amps but we can de-rate-from the 90C column. Say we have 8 current carrying conductor in a conduit that would be 70% * 75amps = 52 amps. We can only use a 50 amp breaker or a 55 amp breaker as long as the load is not greater than 52 amps.
> 
> 
> We do *not* need to start the de-rating from 65 amps which is the 75C column


I thought the original question had to do with Romex which isn't derated with the 90 degree column. What am I missing?

EJPHI


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## Dennis Alwon

EJPHI said:


> I thought the original question had to do with Romex which isn't derated with the 90 degree column. What am I missing?
> 
> EJPHI


Why not? NM is rated 90C but is used at the 60C because the NEC states this however we still derate from the 90C as long as the final overcurrent protective device is not greater than the 60C column.


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## Dennis Alwon

Look at 110.14(C)-- it can't be said any better than that



> (C) Temperature Limitations. The temperature rating associated
> with the ampacity of a conductor shall be selected
> and coordinated so as not to exceed the lowest temperature
> rating of any connected termination, conductor, or device.
> *Conductors with temperature ratings higher than specified
> for terminations shall be permitted to be used for ampacity
> adjustment, correction, or both.*


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## Speedy Petey

EJPHI said:


> I thought the original question had to do with Romex which isn't derated with the 90 degree column.


I hope for your sake you have not been doing it this way the whole time.


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## Ultrafault

Any update op?


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## Dennis Alwon

See if you can get the inspectors to read these posts-- not an in your face thing but to educate them. A good inspector will not be intimidated by our responses and should feel free to post if he/she wants


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## RIVETER

TLinSTL said:


> Is this prohibited anywhere in the NEC? I cannot find anywhere that makes it not allowed, but all of the inspectors around here (multiple jurisdictions)will not allow it. I've been going along with it, drilling a hole for every NM wire.
> 
> What finally put me over the edge was for a house I personally bought in which a city inspector said I had to redo, in the basement, where 2 existing NM wires went through 1 hole in the floor joists. This is in multiple spots and will require a few splices.
> 
> The inspectors can't give me a code reference or any other justification other than that's just the way it is.


If it's your house then time is on your side. Ask for a code reference and move your balls to the front.


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## rookie sparky

cad99 said:


> It is normal here in nd to run two nm's in same hole I drill all my home runs at 3/4" and never heard a complaint but we also have some weird stuff that is not in the nec that inspectors make us do.like tieing up troffers in the grid with painted grid wires.some inspectors really pull the card of being the ahj and demand you do everything there way.
> 
> 
> Sent from my iPhone using Tapatalk


Painted or identified grid wires are required in the instance you mentioned.


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## Ultrafault

Still no update.


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## Shockdoc

Too many stupid people in high places in today's world.


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## backstay

chicken steve said:


> Iirc, all the spray foam insulation spawned the 'rule of 9' as applied to 'romex in hole' , which seem to forgo the usual 24" rule ~CS~


Just talked to the state inspector about this. He said the state(not individual inspectors) consider the hole in the joist the same as 24 inches of contact(conduit, solid material). So four is the max before you derate.


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## chicken steve

I've a similar response on my end of the wired world Backstay

I guess this new spray foam captivates heat rather efficiently , which is their underlying rationale

So i grudgingly conceed bundled conductors subscribe to the rule of 9 as requested, although i have yet to read up on any nrtl level reports

Sometimes i think captive heat in our trade isn't so much a science as it is various kneejerk benchmarks 

That i could stick to this rule, and then install 30-40 home run circuits in one of these just seems skewed to me>>>>











~CS~


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## Inspector Grump

A lot of inspectors should drink less coffee and read more code. I'm a retired inspector and heard horror stories about some other inspectors


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## Lectric

I just ran into this with an inspector, I had 4 nm cables through bored holes and he said I could only have 3. Even after explaining 334.80 to him and doing the math he still said I was wrong, "because you cannot use the 90deg rating" he claimed for nm cable....so I drilled more holes and mumbled obscenities under my breath.....


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## Dennis Alwon

Lectric said:


> I just ran into this with an inspector, I had 4 nm cables through bored holes and he said I could only have 3. Even after explaining 334.80 to him and doing the math he still said I was wrong, "because you cannot use the 90deg rating" he claimed for nm cable....so I drilled more holes and mumbled obscenities under my breath.....


The inspector is incorrect. How can he possibly ignore 334.80 It is pretty clear especially the part I highlighted



> 334.80 Ampacity. The ampacity of Types NM, NMC, and
> NMS cable shall be determined in accordance with 310.15.
> *The allowable ampacity shall not exceed that of a 60°C
> (140°F) rated conductor. The 90°C (194°F) rating shall be
> permitted to be used for ampacity adjustment and correction
> calculations, provided the final derated ampacity does not exceed
> that of a 60°C (140°F) rated conductor*. The ampacity of
> Types NM, NMC, and NMS cable installed in cable tray shall
> be determined in accordance with 392.80(A).


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## Black Dog

Lectric said:


> I just ran into this with an inspector, I had 4 nm cables through bored holes and he said I could only have 3. Even after explaining 334.80 to him and doing the math he still said I was wrong, "because you cannot use the 90deg rating" he claimed for nm cable....so I drilled more holes and mumbled obscenities under my breath.....




Now you can nail him with this...






Dennis Alwon said:


> Here is the article to cite--
> 
> 
> 
> 
> Quote:
> 310.15(B) Tables. Ampacities for conductors rated 0 to 2000 volts
> shall be as specified in the Allowable Ampacity Table
> 310.15(B)(16) through Table 310.15(B)(19), and Ampacity
> Table 310.15(B)(20) and Table 310.15(B)(21) as modified by
> 310.15(B)(1) through (B)(7).
> *The temperature correction and adjustment factors shall
> be permitted to be applied to the ampacity for the temperature
> rating of the conductor, if the corrected and adjusted
> ampacity does not exceed the ampacity for the temperature
> rating of the termination in accordance with the provisions
> of 110.14(C).*
Click to expand...




Dennis Alwon said:


> Look at 110.14(C)-- it can't be said any better than that
> 
> 
> 
> 
> (C) Temperature Limitations. The temperature rating associated
> with the ampacity of a conductor shall be selected
> and coordinated so as not to exceed the lowest temperature
> rating of any connected termination, conductor, or device.
> *Conductors with temperature ratings higher than specified
> for terminations shall be permitted to be used for ampacity
> adjustment, correction, or both.*
Click to expand...


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## crazyboy

Man you should see how many I fit with the 1.5" auger bit I use. :jester::jester:


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## Lectric

My employer and I photo copied and highlighted all of the before mentioned articles, as well as the explanation in the NEC handbook (which shows the exact math examples i used to plead my case). This inspector is a jack of all trades AHJ, he inspects plumbing, electric, building, and hvac. When we go back for final and after he gives us the final sticker he will receive his "information packet"  But what really Pi$$3$ me off is that he said" Now I have to question the rest of your install if your using that kind of math for your circuits".........


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## jimmy21

The fact that your inspector can even do math makes your inspector look like a rocket scientist compared to the one I've been dealing with


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## MetryTiger

I've had one of those guys. He told me no more than 2 cables through a bored hole. I basically shut him down so bad that he walked off the job site and refused to inspect. His boss, who isn't even and electrical inspector, does the inspections now....too funny.


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## macmikeman

On turkey day I drove the family over to wife's cousin's house sitting next to the tee at the 11th hole of a beautiful golf course that I had the pleasure of wiring for them. It was the last of many many houses where I drilled a 2'' thru all the floor joist between the panel and the kitchen area down the long hallway. It's 18 years old now that house. We all rejoiced since that house has not yet burst into flames from all the bundling going on there. Man I hope they make it to next years thanksgiving, the food was terrific.


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## Ultrafault

I have an interview with that same inspection agency next week. Maybe ill tell them how wrong headed they are when I'm there.


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## Pharon

macmikeman said:


> On turkey day I drove the family over to wife's cousin's house sitting next to the tee at the 11th hole of a beautiful golf course that I had the pleasure of wiring for them. It was the last of many many houses where I drilled a 2'' thru all the floor joist between the panel and the kitchen area down the long hallway. It's 18 years old now that house. We all rejoiced since that house has not yet burst into flames from all the bundling going on there. Man I hope they make it to next years thanksgiving, the food was terrific.


I'd be more worried about it structurally collapsing than anything else. Good thing it wasn't a load bearing wall? Leave those to the plumbers.


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