NM cable in EMT

[markf]

Here's an old question that has been around for years. We are installing alot of air conditioner circuits for a local AC contractor. Most of the time we are able to get the circuit through the basement directly to the back of the disconnect. However, there are times that we have to run an additional 10-30 feet on the outside of the house. The local AHJ has demanded that we install a j-box on the outside and convert to THWN conductors. He has admitted that this is not in the code book (NEC) but he read an article on it and the writer "suggested" that NM not be run in conduit because it is not Wet of damp location rated.

Has anyone run into this before? I have been an electrician since 1973 and this is a first for me.

Thanks for your comments

Mark

 

[tomparry]

Re: NM cable in EMT

2002 NEC 334.12(A)(10)d.

Tells you that you are not allowed to install NM in a damp location

 

[russ]

Re: NM cable in EMT

As long as the proper conduit fittings are used outdoors, I can't see how the NM is going to be exposed to the outside elements.

Russ

 

[bphgravity]

Re: NM cable in EMT

NM cable must be supported and secured at intervals not exceeding 4.5 feet and within 12" of every box. This cannot be acheived if installed inside EMT or other conduit systems. NM cable is for normally dry locations and a wiring transition must be made when leaving a dry location to a wet or damp location.

 

[charlie]

Re: NM cable in EMT

The various raceway Articles XXX.22 permit cables to be installed "where such use is permitted by the respective cable articles." 334.10 does not list a raceway installation as an installation method.

This does not prohibit the use of a short piece of raceway to be used as physical protection.

 

[tom baker]

Re: NM cable in EMT

I heard a presentation by one of the CMP members on this subject last fall. he stated that this code rule was a mistake and hoped no one got a violation over it. It wasn't their intent to not allow cable in raceway. In washington state we are going to adopt a local ordinance to correct this problem.
However, short lengths of EMT can be used for physical protction of NM cable.

 

[hurk27]

Re: NM cable in EMT

What is it that deams it as a short run? 6" 6' 10'?

When we go through floors we use a 10" peice,when we sleve exposed romex under the sink or on a island we might use 3' or 5'. But when we protect a drop down a basment o/s wall we can run up to a 10' peice of emt which would depend on how high the basment cieling is. Would we then be required to install a J-Box at every drop down a basment wall? and who will determand what is a short peice is? And if it is allowed to sleve and protect a run down a basment wall how can we prevent it from being used else where when it provides the required protection. As per:334.15 (B)
334.15 Exposed Work.
B) Protection from Physical Damage. The cable shall be protected from physical damage where necessary by conduit, electrical metallic tubing , Schedule 80 PVC rigid nonmetallic conduit, pipe, guard strips, listed surface metal or nonmetallic raceway, or other means. Where passing through a floor, the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing , Schedule 80 PVC rigid nonmetallic conduit, listed surface metal or nonmetallic raceway, or other metal pipe extending at least 150 mm (6 in.) above the floor.

[ March 24, 2003, 06:26 PM: Message edited by: hurk27 ]

 

[goldstar]

Re: NM cable in EMT

Why not run it in UF. That way you won't need a JB. Many times I've had to run a 15 or 20 amp line up to an attic for the AHU and I install UF inside the same piece of aluminum leader that the AC contractor installs to cover the condenser line. If you have to run NM exposed you shouldn't be running standard interior NM cable outdoors but rather UF and I would probably sleeve it in PVC just for protection.

Just my opinion,

Gold Star Electric
Ringwood, NJ

 

[bphgravity]

Re: NM cable in EMT

Hurk, the AHJ is going to determine what is considered a short run. The AHJ in my area considers EMT or other conduit systems being used as sleeved protection compliant up to the 4.5'. This allows for securing of the cable on both ends to meet the requirement of 334.30

Gold Star, how are you supporting and securing the UF inside the cover for the condenser lines? Per 340.10(4), if UF is to be used as NM cable, it must be installed per the provisions of 334, bringing us back to securing the cable.

 

[stamcon]

Re: NM cable in EMT

Goldstar, have you ever had a problem with 300-8
"Installation of Conductors with Other Systems"?

 

[peter]

Re: NM cable in EMT

Perhaps 336-18 Exception No. 1 might apply. If the Romex - I mean non-metalic sheathed cable - is fished, then it doesn't need to be supported.


~Peter

 

[iwire]

Re: NM cable in EMT

We often use this fitting to change from EMT to MC or NM, this connector is not "listed" for NM but we have never been called on it.

 

[goldstar]

Re: NM cable in EMT

Stamcon, I've never been called on section 300.8. Contractors make these same installations every day (that's not to say thay it is correct and to the letter of the code) but the alternative is to run a length of PVC up the side of the house with LB's into the attic and basement. I don't know if the inspectors are just letting us get away with this or that they just aren't citing this section of the NEC.

Bphgravity, section 340.10-3 states that UF is suitable for wet locations. I usually ty-wrap the UF cable to the condenser line before the AC contractor installs the leader. At the bottom, where it becomes exposed, I sleeve it in Carlon flexible (non-metallic )PVC. At that point I can run it into a 60 amp disconnect (if it's for the condenser). If it's for the AHU in the attic I can sleeve a short piece of flex PVC, support it to the side of the house and drill a hole into the basement for the UF cable.

This thread started out with questioning whether we can run NM cable outdoors and/or in conduit. How did we move onto proper support ? Isn't it a safe assumption that we (electricians) are going to properly support a cable or conduit run ?

 

[bphgravity]

Re: NM cable in EMT

Gold Star, I do not mean to come off rude or disrespectful in any way, but one of the main reasons you can't run NM cable in conduit is because it cannot be properly secured and supported. You state that we are suppose to assume that electricians know how to secure systems however you also state that you use "tie wraps" to secure the UF to the condenser lines. I have never seen nor know of a tie wrap that is listed for use with UF or any other cable system as a means of securing it. You also state that you are using another conduit system (condenser lines) as your means to support your cable. Do you really think it is a good idea to do this? What if the A/C contractor needs to make changes and or reapirs? Maybe the AHJ in your area is not citing you on this, but AHJ aren't held resposible even if they pass an installtion, you are.

 

[ed downey]

Re: NM cable in EMT

Let Me Start By Saying I Don't Work On Too Many Residential Projects But After Reading THis Post I Was Just Curious What The Difference Is Between Running Single Conductors (THHN) In Conduit And Running Romex in Conduit? They Are Both Conductors, Although One Has An Outer Jacket. Neither Of These Installations Can Be Supported Inside The Conduit. Is There A Reason That The Code Does Not Permit This Installation? Just Trying To Figure Out The Logic In This Support Topic.

 

[russ]

Re: NM cable in EMT

bph:

Conduit is an approved raceway for conductors.
NM type cables can be fished with out straping in several sections of Article 334.
Without a code reference statings it may not be installed in an approved type raceway, no matter what the length, I just don't see the violation.
MN cable is not used in my area so I have little first hand knowledge of its installation, but by what I read, I could not see how it would be a code violation, in any approved raceway, conduit or wireway without straping. (Except maybe cable tray)

Russ

 

[russ]

Re: NM cable in EMT

We have the same idea Ed, I guess you were posting while I was reading and trying to figure this out myself.

Russ

 

[bphgravity]

Re: NM cable in EMT

ED and RUSS, if conduit is being used as a sleeve or protection for another wiring system ,then it is not called or to be identified as a raceway. 300.18 states that raceways have to be installed complete from junction point to junction point. By stubbing in a piece of conduit in a wall other medium without terminating it with an approved connector, it is not a complete raceway. If you look at any conduit system article at the ".22" section, it states the cables can be installed per the section of that cable. Nowhere in the NM or UF section does it atate that these cables can be installed in a complete raceway system.

 

[vanwalker]

Re: NM cable in EMT

i DO NOT install romex in emt--- as a damp location the wires are now coated as stated--- how do you address the BARE ground wire? GEO

 

[markf]

Re: NM cable in EMT

I can see I opened a can of worms on this one, folks. The intention of my question was to find out if any one has had this problem on a residential AC unit. We do use clamps on the back of the weatherproof box and provide a caulking seal where the box attaches to teh wall. However, on short runs, less than 10', we run from the j-box to the disconnect in NM cable. The code does allow for bare ground conductors but this particular AHJ has no documentation other than an article he read in an engineering magazine.

So the question is: Can we run NM cable through wet or damp locations in EMT, PVC or such, for protection. OR do we need to change over to THWN conductors to satisfy the code? Remember that RT fittings are used.

I appreciate all of your comments.

Thanks

Mark