nm staples

[jetlag]

If I remember correctly you are only supposed to put 1 nm wire under a staple , I was looking at a new house in another county and they had some metal staples about 2 or 3 inches long. They had 5 or 6 nm #12 under same staples in the center of stud , I believe they nailed the staples in slightly first then threaded the nm thru the staples , that way they are stacked in neat. then when finished finished tighten the staple. Isnt that against code, I thought u had to use the stand off brackets for that. to keep the nm 1-1/4 " from edge of stud. Also they had 4 nm #12 s thru 1" hole in center of stud , I think my local inspector said only 2 in a hole, what is code on that

 

[infinity]

If I remember correctly you are only supposed to put 1 nm wire under a staple , I was looking at a new house in another county and they had some metal staples about 2 or 3 inches long. They had 5 or 6 nm #12 under same staples in the center of stud , I believe they nailed the staples in slightly first then threaded the nm thru the staples , that way they are stacked in neat. then when finished finished tighten the staple. Isnt that against code, I thought u had to use the stand off brackets for that. to keep the nm 1-1/4 " from edge of stud. Also they had 4 nm #12 s thru 1" hole in center of stud , I think my local inspector said only 2 in a hole, what is code on that

Two in a hole is not true. Derating is a rather complicated issue. For your question there are a few different parameters involved. One being the number of conductors through a bored hole and how that is related to derating. The other involves when and if the neutral conductor is counted as a current carrying conductor (CCC). Starting with the latter the neutral conductor in a multi-wire branch circuit (MWBC) is sometimes counted as a CCC and at other times it is not. For this question regarding NM cable in a dwelling, where the system is almost always 120/240 volts, the neutral conductor in a 3 wire MWBC is not considered a CCC. Here's the rule from the 2008 NEC:

310.15(B)(4) Neutral Conductor.
(a) A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(B)(2)(a).
(b) In a 3-wire circuit consisting of two phase conductors and the neutral conductor of a 4-wire, 3-phase, wye-connected system, a common conductor carries approximately the same current as the line-to-neutral load currents of the other conductors and shall be counted when applying the provisions of 310.15(B)(2)(a).
(c) On a 4-wire, 3-phase wye circuit where the major portion of the load consists of nonlinear loads, harmonic currents are present in the neutral conductor; the neutral conductor shall therefore be considered a current-carrying conductor.

For a MWBC on a 120/240 volt system 310.15(B)(4)(a) would apply since the neutral conductor carries only the unbalanced current from the other conductors and is not required to be counting when calculating derating.

The second issue is regarding cables through a bored hole in wood. Where the bored hole does not contain fire or draft stopping materials multiple cables through a bored hole do not require any derating. Derating would apply to cables that are bundled together for more than 24" but it would not apply to cables installed through a single hole.

When derating NM cables in a hole that contains fire or draft stopping material the cables can be derated by using their 90 degree C ampacity in table 310.16. For general use with #14 AWG and #12 AWG cables that means that up to 9 CCC's can be installed in that fire or draft stopped hole before derating would have any affect on the cables derated ampacity. That leaves us with the possibility of installing 4-14/3 or 4-12/3 wire cables (8 CCC's) in that hole before derating would actually lower the ampacity level of those conductors below the typical [240.4(D)] 15 amps for #14AWG and 20 amps for #12 AWG cables.

One last caveat in derating is 310.15(A)(2)Exception which tells us that we can disregard the lower adjusted ampacity of the derated cable if it meets the so called 10' or 10% rule but we can leave that for another day.

 

[raider1]

First, as far as staples are concerned, the number of cables permitted under the staple would be a manufactures requirement. (110.3(B))

Second, there is no NEC limit to the number of cable permitted to be installed in holes through studs. If the holes are going to be fire or draft stopped then you must derate the NM cables in accordance with 334.80.

Chris

 

[jetlag]

thanks rob

thanks rob

Two in a hole is not true. Derating is a rather complicated issue. For your question there are a few different parameters involved. One being the number of conductors through a bored hole and how that is related to derating. The other involves when and if the neutral conductor is counted as a current carrying conductor (CCC). Starting with the latter the neutral conductor in a multi-wire branch circuit (MWBC) is sometimes counted as a CCC and at other times it is not. For this question regarding NM cable in a dwelling, where the system is almost always 120/240 volts, the neutral conductor in a 3 wire MWBC is not considered a CCC. Here's the rule from the 2008 NEC:

For a MWBC on a 120/240 volt system 310.15(B)(4)(a) would apply since the neutral conductor carries only the unbalanced current from the other conductors and is not required to be counting when calculating derating.

The second issue is regarding cables through a bored hole in wood. Where the bored hole does not contain fire or draft stopping materials multiple cables through a bored hole do not require any derating. Derating would apply to cables that are bundled together for more than 24" but it would not apply to cables installed through a single hole.

When derating NM cables in a hole that contains fire or draft stopping material the cables can be derated by using their 90 degree C ampacity in table 310.16. For general use with #14 AWG and #12 AWG cables that means that up to 9 CCC's can be installed in that fire or draft stopped hole before derating would have any affect on the cables derated ampacity. That leaves us with the possibility of installing 4-14/3 or 4-12/3 wire cables (8 CCC's) in that hole before derating would actually lower the ampacity level of those conductors below the typical [240.4(D)] 15 amps for #14AWG and 20 amps for #12 AWG cables.

One last caveat in derating is 310.15(A)(2)Exception which tells us that we can disregard the lower adjusted ampacity of the derated cable if it meets the so called 10' or 10% rule but we can leave that for another day.

I dont know where the ahj came up with that. i have always put 3 0r 4 #12 in 1" hole. I wonder if he meant by "hole "a knock out with connector . 2 might be right for that if connector rated for two.

 

[infinity]

I dont know where the ahj came up with that. i have always put 3 0r 4 #12 in 1" hole. I wonder if he meant by "hole "a knock out with connector . 2 might be right for that if connector rated for two.

Yes a connector and a hole are two different animals. There is no set rule on the number of cables you can put in a hole. If hole has no fire or draft stop you can put in as many as will fit. I've heard about inspectors stating no more than X number in a hole but that answer is not often supported by the NEC as written.

 

[jetlag]

thanks raider

thanks raider

First, as far as staples are concerned, the number of cables permitted under the staple would be a manufactures requirement. (110.3(B))

Second, there is no NEC limit to the number of cable permitted to be installed in holes through studs. If the holes are going to be fire or draft stopped then you must derate the NM cables in accordance with 334.80.

Chris

do you know of any long staples approved to stack the nm , if not what method do you use yourself to install several nm on same 2x4 stud.

 

[e57]

do you know of any long staples approved to stack the nm , if not what method do you use yourself to install several nm on same 2x4 stud.

I think I would like the long staple idea - but don't personally know of any.... I use 3M stackers and Caddy CJ's depending on mood and where I'm working... If I have a whole lot in one bay I'll zip tie them to a hanger bar.

 

[Dennis Alwon]

He is where the inspector is probably getting his info.

Where more than two NM cables containing two or more current-carrying conductors are installed in contact with thermal insulation without maintaining spacing between cables, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).

But as Trevor states this means that you could have up to four 2 wire NM in a hole before the derating affects you. The inspector reads this as you cannot have more than 2 wires in a hole. Wrong. It simply states when you have more than 2 you must derate but again so what since it doesn't affect us unless you have more than four 2 wire cables.

 

[Dennis Alwon]

do you know of any long staples approved to stack the nm , if not what method do you use yourself to install several nm on same 2x4 stud.

Avoid bundling and use the stak-its.

 

[raider1]

Avoid bundling and use the stak-its.

That is what I prefer.

I have used a staple and wire tie for 3 cables before, where you pound in the staple and used a wire tie to secure the 3 cables to the staple.

Chris

 

[e57]

Avoid bundling and use the stak-its.

Derating still applies.... Read the bag... More here.

 

[infinity]

He is where the inspector is probably getting his info.

Where more than two NM cables containing two or more current-carrying conductors are installed in contact with thermal insulation without maintaining spacing between cables, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).

But as Trevor states this means that you could have up to four 2 wire NM in a hole before the derating affects you. The inspector reads this as you cannot have more than 2 wires in a hole. Wrong. It simply states when you have more than 2 you must derate but again so what since it doesn't affect us unless you have more than four 2 wire cables.

Where did that info come from?

 

[jetlag]

Thanks infinity

Thanks infinity

Two in a hole is not true. Derating is a rather complicated issue. For your question there are a few different parameters involved. One being the number of conductors through a bored hole and how that is related to derating. The other involves when and if the neutral conductor is counted as a current carrying conductor (CCC). Starting with the latter the neutral conductor in a multi-wire branch circuit (MWBC) is sometimes counted as a CCC and at other times it is not. For this question regarding NM cable in a dwelling, where the system is almost always 120/240 volts, the neutral conductor in a 3 wire MWBC is not considered a CCC. Here's the rule from the 2008 NEC:

For a MWBC on a 120/240 volt system 310.15(B)(4)(a) would apply since the neutral conductor carries only the unbalanced current from the other conductors and is not required to be counting when calculating derating.

The second issue is regarding cables through a bored hole in wood. Where the bored hole does not contain fire or draft stopping materials multiple cables through a bored hole do not require any derating. Derating would apply to cables that are bundled together for more than 24" but it would not apply to cables installed through a single hole.

When derating NM cables in a hole that contains fire or draft stopping material the cables can be derated by using their 90 degree C ampacity in table 310.16. For general use with #14 AWG and #12 AWG cables that means that up to 9 CCC's can be installed in that fire or draft stopped hole before derating would have any affect on the cables derated ampacity. That leaves us with the possibility of installing 4-14/3 or 4-12/3 wire cables (8 CCC's) in that hole before derating would actually lower the ampacity level of those conductors below the typical [240.4(D)] 15 amps for #14AWG and 20 amps for #12 AWG cables.

One last caveat in derating is 310.15(A)(2)Exception which tells us that we can disregard the lower adjusted ampacity of the derated cable if it meets the so called 10' or 10% rule but we can leave that for another day.

It sounds like I need to call the inspector if he objects to nm in the same non fire rated hole and if he objects to 4 or less #12 mn in a fire rated 1" dia hole that would be at the most thru a double plate or 3" of wood . We are talking about #12/2 mn wg not multiwire circuit. Do you agree on this , that 4 #12 is ok on 1" fire chaulked hole?

 

[infinity]

It sounds like I need to call the inspector if he objects to nm in the same non fire rated hole and if he objects to 4 or less #12 mn in a fire rated 1" dia hole that would be at the most thru a double plate or 3" of wood . We are talking about #12/2 mn wg not multiwire circuit. Do you agree on this , that 4 #12 is ok on 1" fire chaulked hole?

If you mean 4-#12/2 cables in a fire stopped hole then yes it would be OK since you have 8 CCC's which would require a derating of 70%.

30 amps * 70% = 21 amps adjusted ampacity.

I don't know on what basis he could form an objection to multiple cables in a hole with no firestop.

 

[Dennis Alwon]

Where did that info come from?

That came from me....:grin: I was just meaning the derating part which I elaborated on. Didn't mean to imply that you stated it as I did. You eventually came around to it, in your last post.

 

[infinity]

That came from me....:grin: I was just meaning the derating part which I elaborated on. Didn't mean to imply that you stated it as I did. You eventually came around to it, in your last post.

Sorry, you had me confused.

 

[Dennis Alwon]

Sorry, you had me confused.

I have a way of doing that.

 

[jetlag]

Thanks all

Thanks all

He is where the inspector is probably getting his info.


But as Trevor states this means that you could have up to four 2 wire NM in a hole before the derating affects you. The inspector reads this as you cannot have more than 2 wires in a hole. Wrong. It simply states when you have more than 2 you must derate but again so what since it doesn't affect us unless you have more than four 2 wire cables.

Im getting confused about who I am quoting , But I think we are on to it now, this is small little hick town in Ga, Im talking about myself to , I live here , and the inspector probably doesnt know how or doesnt want to try to derate the nm thru a fire caulked hole. And we were talking about the fire caulking just before then. He must just use his authority to call the nm allowed in a fire rated hole at 2 so he wont have to even figure the derate. I can live with that if its only the fire caulked holes that he meant but I need to find out. If its non fire caulked holes I need to call him on it. What was that code number that says use table 310.15B2a for nm in contact with thermal insulation ?

 

[raider1]

What was that code number that says use table 310.15B2a for nm in contact with thermal insulation ?

334.80 last paragraph. This is new to the 2008 NEC.

334.80 Ampacity.
The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating. The 90?C (194?F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for 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 392.11.
Where more than two NM cables containing two or more current-carrying conductors are installed, without maintaining spacing between the cables, through the same opening in wood framing that is to be fire- or draft-stopped using thermal insulation, caulk, or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a) and the provisions of 310.15(A)(2), Exception, shall not apply.
Where more than two NM cables containing two or more current-carrying conductors are installed in contact with thermal insulation without maintaining spacing between cables, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).

Chris

 

[jetlag]

Derating still applies.... Read the bag... More here.

Ive used those before . I not sure if the long staples I saw in savannah Ga were even electrical staples, I cant find them on the internet, only staples for 2 cables. I liked the idea of the long staples because would be much less expensive that the cable supports. If any one finds romex metal staples for more than 2 nm s please post