Does anyone have any insight on whether the code prohibits NM-B wire to be run inside EMT? I have heard conflicting arguments but I am not sure. A contractor installed this in my unfinished basement and it did pass inspection. Just trying to make sure it is ok.
-
Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades
Electrical Metallic Tubing
- Thread starter mam1869
- Start date
raider1
Silver Member
Re: Electrical Metallic Tubing
NM cable is permitted to be installed in EMT.
Take a look at NEC sections 334.15(B) and 334.15©.
Make sure that the NM cable meets the conduit fill requirements of 358.22.
Chris
NM cable is permitted to be installed in EMT.
Take a look at NEC sections 334.15(B) and 334.15©.
Make sure that the NM cable meets the conduit fill requirements of 358.22.
Chris
vegas paul
Silver Member
Re: Electrical Metallic Tubing
Not sure what NM-B is, but per NEC 334.15 (B), NM, NMC and NMS are required to be protected from damage, and EMT is listed as one of the acceptable methods to accomplish this. So, assuming you have NM, NMC, or NMS, in EMT installed in your basement, you should be ok (as long as the ampacitywas calculated correctly, EMT supported properly, etc.).
Not sure what NM-B is, but per NEC 334.15 (B), NM, NMC and NMS are required to be protected from damage, and EMT is listed as one of the acceptable methods to accomplish this. So, assuming you have NM, NMC, or NMS, in EMT installed in your basement, you should be ok (as long as the ampacitywas calculated correctly, EMT supported properly, etc.).
chris kennedy
Sawhorse
Re: Electrical Metallic Tubing
Also not prohibited by 334.12.
Also not prohibited by 334.12.
raider1
Silver Member
Re: Electrical Metallic Tubing
The -B designation on NM-B denotes that the NM cable is constructed with conductors that have 90 degree rated insulation in accordance with 334.112. There is a FPN to that section that has that information.
Here is what it says:
The -B designation on NM-B denotes that the NM cable is constructed with conductors that have 90 degree rated insulation in accordance with 334.112. There is a FPN to that section that has that information.
Here is what it says:
Chris
vegas paul
Silver Member
Re: Electrical Metallic Tubing
thanks raider1 - never saw that!
thanks raider1 - never saw that!
raider1
Silver Member
Re: Electrical Metallic Tubing
Your very welcome.
Chris
Your very welcome.
Chris
jar546
Forum Coordinator
Re: Electrical Metallic Tubing
Is the emt inside or outside the structure?
Is the emt inside or outside the structure?
chris kennedy
Sawhorse
Re: Electrical Metallic Tubing
Pointing out that NM can be installed in conduit in concealed work also.mam1869 said:
Guest
Re: Electrical Metallic Tubing
A while back I raised this issue with the Chief Electrical Engineer of my AHJ. My concerns are heat dissipation, conduit fill {no cross sectional area is listed in the code} and damage to the outer jacket from pulling it through conduit. The CEE has contacted UL. No answer yet.
I am not aware of any prohibition that has ever been in any code and the code has always allowed it "for protection". That permission has been taken to mean that other than "for protection" it was not allowed. We have allowed it for short sections such as passing through a rated wall in an attic but not as a general rule. Since we work at the speed of government, it will be a while longer before I know more.
The added friction of the jacket makes the practice unlikely to catch on and so far it has seldom been an issue.
A while back I raised this issue with the Chief Electrical Engineer of my AHJ. My concerns are heat dissipation, conduit fill {no cross sectional area is listed in the code} and damage to the outer jacket from pulling it through conduit. The CEE has contacted UL. No answer yet.
I am not aware of any prohibition that has ever been in any code and the code has always allowed it "for protection". That permission has been taken to mean that other than "for protection" it was not allowed. We have allowed it for short sections such as passing through a rated wall in an attic but not as a general rule. Since we work at the speed of government, it will be a while longer before I know more.
The added friction of the jacket makes the practice unlikely to catch on and so far it has seldom been an issue.
Re: Electrical Metallic Tubing
Since we're talking about EMT, I'll refer to Section 358.22, but other raceways have similar language. 358.22 specifically allows cables to be installed in EMT where not prohibited by the respective cable article. As Chris Kennedy pointed out, it is not prohibited by the NM article. Of course, it would not be allowed where the EMT is located in a wet or damp location, since NM is not permitted in a wet or damp location.
As for calculating conductor fill within the raceway, Note 9 found at the beginning of chapter 9 tell us how it is to be done.
Since we're talking about EMT, I'll refer to Section 358.22, but other raceways have similar language. 358.22 specifically allows cables to be installed in EMT where not prohibited by the respective cable article. As Chris Kennedy pointed out, it is not prohibited by the NM article. Of course, it would not be allowed where the EMT is located in a wet or damp location, since NM is not permitted in a wet or damp location.
As for calculating conductor fill within the raceway, Note 9 found at the beginning of chapter 9 tell us how it is to be done.
raider1
Silver Member
Re: Electrical Metallic Tubing
As for the conduit fill, Note 9 to Table 1 says that a multiconductor cable of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on using the major diameter of the ellipse as a circle diameter.
If conduit fill is applied properly. then you should have no more problem with damage to the outer jacket then if you were pulling in single conductors.
Installing NM cable in raceways is not a common practice, but it does have it's applications.
Keep in mind though that if the raceway is in a damp or wet location then you can't install NM cable in those raceways.
Chris
Heat dissipation is no more of an issue with NM cable in a raceway then if I install NM cable buried in thermal insulation.
As for the conduit fill, Note 9 to Table 1 says that a multiconductor cable of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on using the major diameter of the ellipse as a circle diameter.
If conduit fill is applied properly. then you should have no more problem with damage to the outer jacket then if you were pulling in single conductors.
Installing NM cable in raceways is not a common practice, but it does have it's applications.
Keep in mind though that if the raceway is in a damp or wet location then you can't install NM cable in those raceways.
Chris