Installing romex in EMT conduit

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Jpflex

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Victorville
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Electrician commercial and residential
when I was an apprentice my boss told me he better never see me put romex (with Its Jacket) into an emt conduit as you would with normal individual insulated wires. I assumed this was a code violation at that time.

However, after reading NEC years later I found that there are situations romex is to be protected by a steel sheet atleast 1/4” thick or When entering a floor hole to be protected by a metallic conduit sleeve.

I have also not found a code (not mentioning fill limit code) that specifically says romex cannot be put Into EMT or conduit. Is this correct?

I also recently passed romex through a double gang metallic box without breaking wires out of jacket, straight in left to exit rear. Code requires equipment to be bonded if likely to be energized but since the conductors are insulated in their Factory jacket, would you still need bonding here?
 

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letgomywago

Senior Member
Location
Washington state
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residential electrician
Also its actually a violation to run nmb conductors without the sheath but many do this. The conductors aren't identified with gauge like thhn and others are.
 

mlnk

Senior Member
It is Code legal to run NM cable in any type of conduit. See Chapter 9 Tables. The limit on fill is 53%. Measure the major diameter of elliptical cables as the diameter. This means one 12-2wG in 1/2" EMT, but I would use 3/4 EMT especially if there are bends.
 

Jpflex

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Location
Victorville
Occupation
Electrician commercial and residential
The company I work for only buys THHN but according to code this 75 degree wire is too high for typical installations? Such as terminating on standard 15 to 20 ampere receptacles? Even with ampere derating, what kind of wires should be bought for 60 degrees?
 

roger

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Retired Electrician
The company I work for only buys THHN but according to code this 75 degree wire is too high for typical installations? Such as terminating on standard 15 to 20 ampere receptacles? Even with ampere derating, what kind of wires should be bought for 60 degrees?
You are being told wrong. You can use a conductor with higher rating for anything below it's rating, you can not use a conductor with a lower rating for a higher usage. IOW's using a 60 deg conductor on a 75 deg termination is not allowed however vice versa is.
 

Jpflex

Senior Member
Location
Victorville
Occupation
Electrician commercial and residential
You are being told wrong. You can use a conductor with higher rating for anything below it's rating, you can not use a conductor with a lower rating for a higher usage. IOW's using a 60 deg conductor on a 75 deg termination is not allowed however vice versa is.
But nec says you cannot terminate a conductor with a higher temperature rating than the temperature rating of the point or component of termination unless for cases of ampacity adjustment derating on the conductor
 

Jpflex

Senior Member
Location
Victorville
Occupation
Electrician commercial and residential
If it's a sleeve for physical protection yes and you need 1/4 inch of it to enter the box. I only ever do it this way in basements or shops when nm was cheaper than mc by a lot.
The fill calculation in nec takes into account bare wired but as far as I know doesn’t include NM cable jackets so how can you determine the number of NM cables allowed to fill a conduit if allowed?
 

Jpflex

Senior Member
Location
Victorville
Occupation
Electrician commercial and residential
It is Code legal to run NM cable in any type of conduit. See Chapter 9 Tables. The limit on fill is 53%. Measure the major diameter of elliptical cables as the diameter. This means one 12-2wG in 1/2" EMT, but I would use 3/4 EMT especially if there are bends.
Code takes into account insulated wires but not the NM cable jackets, obviously no cables with sheath jacket will fill faster than typical insulated wires. Nec table gives fill calculation for typical wires but not jackets?
 

roger

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Fl
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Retired Electrician
But nec says you cannot terminate a conductor with a higher temperature rating than the temperature rating of the point or component of termination unless for cases of ampacity adjustment derating on the conductor
No it doesn't, read it again.
 

roger

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Fl
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Retired Electrician
The fill calculation in nec takes into account bare wired but as far as I know doesn’t include NM cable jackets so how can you determine the number of NM cables allowed to fill a conduit if allowed?
Read the Notes to Tables in chapter 9
 

Buck Parrish

Senior Member
Location
NC & IN
when I was an apprentice my boss told me he better never see me put romex (with Its Jacket) into an emt conduit as you would with normal individual insulated wires. I assumed this was a code violation at that time.

However, after reading NEC years later I found that there are situations romex is to be protected by a steel sheet atleast 1/4” thick or When entering a floor hole to be protected by a metallic conduit sleeve.

I have also not found a code (not mentioning fill limit code) that specifically says romex cannot be put Into EMT or conduit. Is this correct?

I also recently passed romex through a double gang metallic box without breaking wires out of jacket, straight in left to exit rear. Code requires equipment to be bonded if likely to be energized but since the conductors are insulated in their Factory jacket, would you still need bonding here?

Perhaps your old boss was thinking of an outdoor installation.
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
But nec says you cannot terminate a conductor with a higher temperature rating than the temperature rating of the point or component of termination unless for cases of ampacity adjustment derating on the conductor
Code Reference?
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
1) Conduit fill with cables: For conduit fill calculations you treat non-round cables as if they were round with a diameter equal to the largest 'diameter' of the cable. You treat a 0.14"x0.4" 12/2 NM cable as if it were round with a diameter of 0.4"

2) The temperature rating of a conductor is the maximum operating temperature permitted for that conductor. A '75C' conductors operating temperature will depend on the current flowing in the conductor and ambient conditions. If you operate than 75C conductor with '60C current', then its operating temperature will be 60C.

You are not allowed to have a conductor with > 60C operating temperature on a 60C terminal. The 60C terminal limits you to a 60C operating temperature. So you are permitted to have a 75C conductor on a 60C terminal, but are limited to '60C current'.

For example if you have 8ga Cu 75C wire (ampacity 50A) terminated on a 60C breaker terminal, then you are kosher if current is 40A or less.

-Jon
 
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