Why Using Romex (NM) cable in Conduit Violates Electrical Codes

for electricians and DIY enthusiasts alike is the appropriateness of using Romex® within conduit, a practice often debated and scrutinized within the context of building codes and safety standards. The crux of the matter lies in understanding the nature of Romex® wire and the regulatory guidelines governing its use.
Understanding Romex® Wire
Romex® wire is designed for quick and safe installation in dry locations. It's available in various lengths and sizes, such as the Southwire Romex SIMpull 250-ft 12/2 Non-Metallic Wire and the Southwire 15 ft. 14/2 Solid Romex SIMpull CU NM-B W/G Wire, among others. These products are intended for exposed or concealed installations within residential buildings, offering a flame-retardant and crush-resistant solution for branch circuits to outlets, switches, and other loads.
The Debate Around Romex® in Conduit
The question of whether or not Romex® can be run in conduit hinges on several factors, primarily related to building codes and the specific requirements of a given installation. Here are key points to consider:
Heat Dissipation: Romex® wire, being encased in a non-metallic sheath, is designed to dissipate heat into the air around it. When placed inside conduit, especially for extended lengths, the ability of the wire to cool effectively is reduced. This can lead to overheating and potential fire hazards.
Building Codes: The National Electrical Code (NEC) provides guidelines on the appropriate use of electrical wiring and materials. While the NEC does not outright prohibit the use of NM cable within conduit for certain protective applications, it specifies conditions under which wiring methods should be used to prevent potential hazards. It's crucial to consult the latest edition of the NEC or a local building inspector for the specific regulations applicable to your area.
Practicality and Cost: Running Romex® inside conduit may not be practical or cost-effective compared to using wire types that are better suited for conduit installation, such as THHN or XHHW wires. These alternatives are designed for conduit use, providing easier pulls through the conduit and better heat dissipation.
Conclusion
While Romex® offers a convenient and reliable wiring solution for many residential applications, the practice of running it inside conduit should be approached with caution. It's essential to prioritize safety and adherence to local building codes above all. In cases where conduit is required for protection or other reasons, selecting the appropriate wiring method that aligns with regulatory standards and installation best practices is critical. Always consider consulting with a professional electrician or local building authority to ensure that your electrical projects are both safe and code-compliant.
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[@martinmccabe177]

Situation: Old house with knob and tube wiring. Just removed fuse panel and install breaker panel. Two "if legal?" questions: House has hot water heat, can I run Romex from basement up along sides of the cool return lines from the radiators. They are only barely warm to the touch. There is plenty of room in these pipe holes through the floors. In "non damp" areas such as the bedrooms can I run 12-2 Romex through raceways for surface mounted outlet boxes. "Not in bathroom or kitchen and not outside" Thanks

[@toolsandtactics]

new construction subs it out for acs and different whips, some jurisdictions gave up and calling it and allows the few feet for whips but outside for more than 3ft is probably uncalled for good to see ya!

[@fauxque5057]

I'm waiting for the NEC to come and kick down my door. I have lots of things that goes against their code. Even a few outdoor outlets that aren't gfci protected anymore. OMG! I even have a 15' run of direct burial romex in a 3/4" pvc electrical conduit that's running around the inside edge of my patio. Come and get me NEC.

[@mikieboyblue]

Welcome back! I'll only put it in for short runs down a block wall for protection and serviceability after soray foam for example. Open in the top. Less than 3 ft. I believe that is accepted.

[@yessir640]

Why do Manufacturers make Conduit to Romex Connectors then?

[@abrelectric]

Not for outdoor applications

[@mattmck5496]

I have a somewhat complicated DIY question. I recently replaced a 80 ft run for a residential stove which had been # 6, 2 wire copper W/G , ( 2 Hots, no neutral) . 1/2 of the run mounted to the exterior of the house and the other 1/2 thru the basement and into a J Box for the last 7 feet of the run to the stove . None of the run was in conduit. I was able to reduce the original run from 80 to 55 ft and replaced the #6 2 wire with #8 3 wire up to the J box. Here is my question. I used #8 THHN wire from the J - box to the stove, for the last 7ft of the run and installed the THHN in 1" conduit. My question is whether the THHN is going to be trouble down the road , and/or whether it is code compliant. It works fine for the time being , measuring 32Amps at the main panel, for the 5 min I maxed it out, but I'm worried about trouble later on. Thanks, McK52749

[@DanielinLaTuna]

Loved your Zinsco panel video

[@darrelriley]

I need to run multiple lines from an outdoor heat pump disconnect box to four separate indoor ceiling recessed mini splits. Mitsubishi requires the wiring to be double insulated, stranded 14/3 with a ground wire, and rated for 600V. actual voltage is 220v. To ensure protection, I plan to use conduit for the wiring, which will be installed in an old attic space. The point here is , i need to use romex (to comply with double insulated) and it would be best installed in conduit to protect the runs in attic. What do you think.

[@abrelectric]

Why not use what Mitsubishi is asking for, in conduit? Will using Romex void your warranty? Also, is there a permit/inspector involved? Is that going be super hot in the summer?

[@darrelriley]

I want it to be done right as if there was an inspection. This is in seattle area but attic still reaches 120 degrees in summer. What i am proposing meets Mitsubishi requirements, though I’m not sure i can find romex in stranded, i just want it to meet code.

[@abrelectric]

@darrelriley As long as it's not in a wet environment, and the fill percentage is right (12/2 in 1/2" conduit or larger). What kind of conduit are you using in the attic?

[@pld8993]

@@darrelriley You should use mini split cable, which is a flexible cord with stranded conductors. You run it right along with the linesets from the outdoor unit to each head. HVAC supply house will have it. There's no need for conduit, just zip tie it to the linesets.

[@junliu4207]

may i use #6/3 nmwu wire for indoor subpanel please

[@abrelectric]

Absolutely. As long as your breaker is 50 amps or less, the 6/3 is in a dry location, and inside a wall or in correctly sized conduit.

[@goodtimes2654]

So what do you do if you have this condition. I have all romex feeding my 200 amp panel through a 2 1/2” conduit which use to be legal. Is it safe or not or grandfathered or not ?

[@abrelectric]

Is it romex or SER cable?

[@michaeladams9129]

So do we just need to use lube?

[@abrelectric]

Lots

[@jameslulewich9318]

first , great instructional videos. i have a question,i am wiring a new kitchen, and have to run 6 circuits( 5 12-2 and 1 14-2 for a microwave dishwasher, refrigerator 2 outlet circuits and lighting). 10 feet of the run is extremely difficult to access but i have been able slide a 2 inch pvc electrical conduit through which makes the 6wires very easy to fish through . the pipe is in the basement, a dry area , and will be open at both ends. i thought that this wuold be the best solution , as the run, i fear i loaded with exposed nails and screws ( poorly framed bathroom and laundry area LOL) i get so many opinions on this matter! thanks ,

[@user-ll1vj7qo1m]

If the conduit is 24 inches or less in length its fine, but if over 24 inches you will need to adjust the ampacity of the cables. 6 current carrying conductors need an ampacity adjustment of 80%. #12 is rated for 30 amps after the adjustment still rated 24 amps and 20 a breaker is ok. The #14 is derated from 25 amps to 20 amps and a 15 amp breaker is ok. You should be fine as long as a temperature adjustment isn't required.

[@pld8993]

@@user-ll1vj7qo1m You're wrong but don't worry, I gave him accurate advice.

[@pld8993]

You get many opinions and on this forum you got bad advice, it seems. Ignore @user-ll1vj7qo1m, he's wrong. There are 12 current carrying conductors in those cables, not 6, because both hots and neutrals are current carrying. The ampacity adjustment for 12 conductors is 50% so #12s will be limited to 15 amp breakers. For any 20 amp circuits you'll need #10. The #14 cable is a little more complicated. It gets adjusted down to 12.5 amps but since there is no such thing as a 12.5 amp breaker, you can install the next higher sized breaker, which is a 15. However, this #14 circuit is limited to 12.5 amps continuous loads or 10 amps noncontinuous loads. Seems like the 14 is for lighting so it will be fine on a 15 amp breaker. If use slide in two 3/4" or 1" conduits (instead of a single piece of 2") and split the cables up into 3 in each one, then 12 and 14 are good for your 20 amp and 15 amp circuits, respectively.

[@user-ll1vj7qo1m]

@@pld8993 Reading directly from the code book here. Article 310.15(E)1) Neutral conductor: " 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 of310.15 (C) 1). I teach electricity at a college and as a former Georgia and Florida Master electrician, I think I am qualified to give advice in this forum. What are your qualifications to give advice sir?

[@pld8993]

@@user-ll1vj7qo1m You, conveniently perhaps, left out the first sentence, "Neutral conductors shall be considered current carrying in accordance with any of the following." In the case of an individual circuit (one hot, one neutral), the neutral is carrying all the current from the ungrounded conductor and is NOT carrying "only the unbalanced current from other conductors of the same circuit." 310.15(E)(1) exempts only neutrals carrying only unbalanced current so treating the neutral of an individual circuit as current carrying, per the first sentence, is in accordance with all of 310.15(E). Put an amprobe on the neutral of an individual circuit carrying 5.3 amps, for example, and you'll read 5.3 amps. For clarification, you may to look up the definition of unbalanced current and also individual circuit, which seem to be the source of your confusion, as there is no unbalanced current in an individual circuit. My qualification to give advise on some random youtube forum is the fact that I have a computer. However, I've been in the trade for over 40 years, got my first master license when I was 22 and have had one in 6 different states throughout the years although currently only 3 states, been teaching the NEC for 25+ years, for the last 10+ years I've been working with NJATC on curriculum review and revisions, and I'm still out in the field every day so I'm not a former anything. Yes, that makes me an expert. So much for whose is bigger, nice try.

[@eddieo9424]

Why would you pull romex thrue a conduit. I have never after 35 years in the ibew worked with someone who did that . Pull wire . And if you are concerned about pipe fill just install a bigger pipe for example 4 #10 What size pipe. And pvc is ok to to trench or install under ground .I did not say pvc . In concrete .so you can always up the size of pipe .

[@electricalron]

to protect the cable from physical damage.

[@eddieo9424]

How about not using romex at all and pull wire.

[@electricalron]

@@eddieo9424 romex is wire

[@KLAWNINETY]

When you're shacking a house you run Romex through the wall and then poke outside and run conduit to your exterior load, typically A/Cs.

[@eddieo9424]

I use 1900 boxes inside, pipe back to the panel steel ridgid Pipe thru the wall, to outside weather proof rated disco. Seal tight to the ac compressor. That's how I was trained to pipe homes . People dwelling. Pipe last longer in a fire and people have more time to evacuate. Romex burns toxic smoke. If your not just call your fire department and ask.

[@mothman-jz8ug]

And I am telling you, you are wrong. Site the actual code text that prohibits romex in conduit. Nobody has ever been able to do this - not a single one of the many great oracles who know everything. Why do this? Running conduit all over the house might be a tad costly, but there may be a place or two where PHYSICAL PROTECTION might make the conduit a valuable commodity. So, run the romex as usual, run it through conduit where safety dictates, then go back to open romex. No boxes needed; no splices between wire types involved, just protect where necessary. Conduit fill? That applies REGARDLESS of wire type. Of course you follow it when running one wire or twenty and regardless of gauge, etc. Sooo...You still haven't shown how romex in conduit violates code. There IS a place where it could make a difference, and this applies to electrical wiring, telephone wiring, co-axial, or any other wire and that is in commercial buildings. It falls under different fire codes, not simply electrical, and has to do with the insulation type. Some give off highly toxic fumes when burnt, and are forbidden in air plenums, as well as conduit or raceways, etc. But that isn't NEC.

[@abrelectric]

I did site the Code, in several videos. I am not saying to never install romex on conduit. Most of the issues, again, are running romex in a damp/wet location.

[@pld8993]

This guy has several videos on this same topic, look it up, and every one of them has a title that says that romex is illegal in conduit, but he then pivots to wet locations in the video. He knows better, he's just trolling for clicks for $$$.

[@user-ll1vj7qo1m]

if conduit is physically underground it's a wet location and type NM romex doesn't meet code, UF cable must be used, but there are other uses such as outlets inside a block construction garage that will always be sleeved with conduit of some type. Heat dissipation isn't an issue unless you have 4 or more romex runs in one conduit.

[@pld8993]

Derating occurs with 2 or more romex cables (more than 3 current carrying conductors), not 4.

[@user-ll1vj7qo1m]

@@pld8993 Not the case NEC 310.15 (E) covers the neutral. A neutral in a 2 wire romex with ground does not count as current carrying. I suggest you buy a code book and read it to clear up the confusion

[@pld8993]

​@@user-ll1vj7qo1m 310.15(E) says the following, "Neutral conductors SHALL be considered current carrying in accordance with the following." Since E(2) and E(3) are explicitly referring to circuits with multiple hots, not individual circuits, we can exclude them from this discussion and focus on E and E(1) solely. E(1) provides nothing more than a justification for exclusion from the requirement that "neutrals SHALL be considered current carrying." E(1) excludes neutrals that are carrying "ONLY the unbalanced current from other conductors" from being counted. Unbalanced current can occur when a single neutral serves multiple hots. In an individual circuit with one hot and one neutral, there is no possibility of unbalanced current (assuming everything's done and working properly), 3.2 amps through the hot results in 3.2 amps through the neutral, for example, therefore only the first sentence in 310.15 applies to individual circuits, which clearly states that a neutral SHALL be considered current carrying. Since an individual circuit doesn't meet the conditions for exclusion laid out in E(1), and neither E(2) or E(3) applies to individual circuits, the neutral in an individual circuit is not excluded from the requirement that "Neutral conductors SHALL be considered current carrying..." The NEC is not written for amateurs or the general public. It's written for professionals and knowing how to apply the NEC requires experience and comprehension of terms like shall (which the NEC defines), or only, for example. I suggest you take a reading comprehension course, followed by an NEC course, to clear up the confusion you're experiencing. I've been teaching the NEC for 30 years so I have plenty of codebooks and have read every word multiple times, but thanks for the advise, junior.

[@pld8993]

@@user-ll1vj7qo1m You're wrong. Which part of "Neutral conductors SHALL be considered current carrying" do you not understand?

[@user-ll1vj7qo1m]

@@pld8993 310.15 (E) says they're not for the purposes of ampacity adjustments. Hacks like you shouldn't be commenting at all.

[@cafemolido5459]

SO, this video is what you cannot, then what can you?

[@abrelectric]

A lot! Romex in the interior, dry locations. UF or THW/MTW in conduit for damp-wet locations.