# Romex Running Across Duct



## wildleg

it might not be a violation of the NEC, but it could very well be a mechanical or building code violation


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## Shockdoc

stl100 said:


> Hey guys,
> 
> New to the board. I look forward to learning everything I can. Does current code state anywhere that you can't run romex under metal duct work. Current branch wires are in contact. No damage no sharp edges around but I'm wondering if duct becomes hot enough... it could melt the jacket and electrify the duct which may electrify the registers. Am I thinking straight? I'm from St. Louis MO.


Not that I have done it but I have seen NM cables run with steam lines with no meltdown , as long as your ductwork is not a hi temp gas exhaust you should have no problems.


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## 480sparky

Do your ducts get 168°F? :blink:


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## stl100

480sparky said:


> Do your ducts get 168°F? :blink:


LOL No... So I guess my question is then if not within the NEC if somehow the jacket was stripped could the wires energize the duct/registers in the home? I know people who are under that impression.


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## Shockdoc

stl100 said:


> LOL No... So I guess my question is then if not within the NEC if somehow the jacket was stripped could the wires energize the duct/registers in the home? I know people who are under that impression.


If it makes the people feel better, sleeve a 20" piece of rmc with plastic bushings on it crossbay wherever a duct passes.:jester:


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## ohiosparky99

stl100 said:


> LOL No... So I guess my question is then if not within the NEC if somehow the jacket was stripped could the wires energize the duct/registers in the home? I know people who are under that impression.


Sure, if the duct was somehow not grounded and came in contact with a energized circuit, it then would just become an extension of the circuit,


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## RIVETER

stl100 said:


> Hey guys,
> 
> New to the board. I look forward to learning everything I can. Does current code state anywhere that you can't run romex under metal duct work. Current branch wires are in contact. No damage no sharp edges around but I'm wondering if duct becomes hot enough... it could melt the jacket and electrify the duct which may electrify the registers. Am I thinking straight? I'm from St. Louis MO.


I l have worked in houses where the entire duct work was energized by a poorly installed branch circuit. The same house was totally energized on the aluminum siding, as well. I considered that a good catch.


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## etb

480sparky said:


> Do your ducts get 168°F? :blink:


120-130 degF is normal for gas heat, lower for strip, lower yet for heat pump.

Did get a call for melted NM across some ducts though; no shorts just darkened & flattened jacket. 30s home (coal) retrofitted with outdoor packaged unit. Earlier they replaced it and bumped up the BTUs but didn't upsize the ductwork. High limit kept triping so the genius HO jumpered it. His package caught fire; luckily the house had a weird gravel type stucco.


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## BBQ

etb said:


> His package caught fire.


That has to hurt.


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## Cletis

*material*

I run a proprietary material that dissapates heat and is non conductive in between the romex and duct


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## McClary’s Electrical

Cletis said:


> I run a proprietary material that dissapates heat and is non conductive in between the romex and duct


 
like what?


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## RGH

..romex....:blink:...why not just slack it enough so it don't touch the duct work...??..a half inch would be plenty....I have done it that way for 3 decades.....I have never had a call back for a melted h/r....seems odd...plenum temp maybe 180...but temp of duct down stream I would think would be way less....have seen ho's and contractors use steel studs(basement finishing) and just butcher romex more than once...


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## RGH

mcclary's electrical said:


> like what?


http://www.bing.com/images/search?q...FC5D1614352E03CB450143AB551957E0E&FORM=IQFRBA this works great for heat...epa guys don't like it so much:whistling2:


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## Alhenry92

it all depends on how the wire is being used, how the wire is run, and how the duct itself is being used. Article 300.22(A) through (D) specifies this in the 2011 NEC


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## BBQ

Alhenry92 said:


> it all depends on how the wire is being used, how the wire is run, and how the duct itself is being used. Article 300.22(A) through (D) specifies this in the 2011 NEC


I don't think anything in 300.22 addresses cables run outside or 'on' a duct.


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## Alhenry92

http://www.cccassoc.org/blog/wp-content/uploads/2010/11/CCCA_2011_NEC_White_Paper_11-04-2010.pdf


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## McClary’s Electrical

Alhenry92 said:


> http://www.cccassoc.org/blog/wp-content/uploads/2010/11/CCCA_2011_NEC_White_Paper_11-04-2010.pdf


 
Dude that's for plenums.


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## BBQ

Alhenry92 said:


> http://www.cccassoc.org/blog/wp-content/uploads/2010/11/CCCA_2011_NEC_White_Paper_11-04-2010.pdf


Which part of 300.22 applies to the opening posters question?




> Does current code state anywhere that you can't run romex *under metal duct work*. Current branch wires are in contact.


Under is not 'in' and 300.22 is about wiring methods 'in' ducts.


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## Shockdoc

How bad is it if someone cut a GFCI in a kitchen backsplash and found a full cavity metal duct in the bay. Then proceeded to drill a 7/8 hole in the bottom of it and run romex up to a box a GFCI ?


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## McClary’s Electrical

Shockdoc said:


> How bad is it if someone cut a GFCI in a kitchen backsplash and found a full cavity metal duct in the bay. Then proceeded to drill a 7/8 hole in the bottom of it and run romex up to a box a GFCI ?


 

Cash, no receipts...


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## Neoursa

Keep it seperate. Why have to go calc and derate?

On some renos I've had to go back and reroute lines after plumbers made changes and ran hot water baseboard pipes on my lines. Costly one was an oven home run recently.


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## BBQ

Neoursa said:


> On some renos I've had to go back and reroute lines after plumbers made changes and ran hot water baseboard pipes on my lines. Costly one was an oven home run recently.


Why would you have to move them, NM is rated 90C, I doubt the pipes were above that.


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## mbednarik

my high eff gas furnace has a max output temp of 130 deg. I wouldn't worry about it.


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## Neoursa

They can't be touching. Last time, they wedged the 6/3 oven homerun at several points against copper pipers not far from the boiler. So I factored in at least 140F ambient so I'd have to correct .71 or so as per 310.

I caught it before the drywall went up.


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## mtylerb

stl100 said:


> Hey guys,
> 
> New to the board. I look forward to learning everything I can. Does current code state anywhere that you can't run romex under metal duct work. Current branch wires are in contact. No damage no sharp edges around but I'm wondering if duct becomes hot enough... it could melt the jacket and electrify the duct which may electrify the registers. Am I thinking straight? I'm from St. Louis MO.


I get that you're under the NEC. The CEC rule 12-506(4) and (5) specifies:



> *Section 12 - Wiring Methods
> *
> 
> *Non-metallic-sheathed cable*
> 
> *12-506 Method of installation (see Appendices B and G)*
> ...
> (4) Where non-metallic-sheathed cable is run in proximity to heating sources, transfer of heat to the cable shall be minimized by means of an air space of at least(a) 25 mm between the conductor and heating ducts and piping;
> (b) 50 mm between the conductor and masonry or concrete chimneys; or
> (c) 150 mm between the conductor and chimney and flue cleanouts.​(5) Notwithstanding Subrule (4), a thermal barrier conforming to the requirements of the _National Building Code of Canada_ or local building legislation shall be permitted to be installed between the conductor and heating sources to maintain ambient temperature of the conductor at not more than 30C.​




Do you guys not have anything similar?​


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## BBQ

mtylerb said:


> Do you guys not have anything similar?


Nope, why would we need too?


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