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#96153 - 11/07/05 12:06 AM Flexible Metal Conduit  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Should the inspector write you a violation for installing NM cable in FMC for an installation where the metal box is in a cold air return and the connection involved an angle connector inside the wall? Code reference 348.42 says yes, but why?


George Little

2017 / 2014 NEC & Related Books and Study Guides

#96154 - 11/07/05 12:49 AM Re: Flexible Metal Conduit  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,058
Estero,Fl,usa
Are they are just saying FMC is a raceway system and you can't push wire through an angle fitting without taking the cover off. You couldn't do that if it was in the wall.

Just a guess


Greg Fretwell

#96155 - 11/07/05 09:46 AM Re: Flexible Metal Conduit  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
For a flex 90 in a wall, it is the same as having an LB fitting in a wall. That point of the raceway is not accessible. It is the same as burying a j-box in the wall.

I would want to know more about this box in the plenum? Is it allowed there under 300.22?


Mark Heller
"Well - I oughta....." -Jackie Gleason

#96156 - 11/07/05 10:57 AM Re: Flexible Metal Conduit  
boggerbutt2454  Offline
Member
Joined: Feb 2005
Posts: 44
Concord NC USA
Romex is not premitted in plemun rated ceiling. It would be the same as running romex in liquid tight flex outside. Romex is not rated for wet locations.


#96157 - 11/07/05 11:04 AM Re: Flexible Metal Conduit  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
This is a residential application and the cold air return would fall under "Other Space Used for Environmental Air." Reading 300.22(C)(1). Wiring methods include FMC and the contractor sleeved the last two feet of NM cable when entering the CA and terminates in a metal device box. There probably would never be a situation where the electrician would be withdrawing the NM cable from the FMC unlike a situation where single conductors might be installed. I don't see any safety issues here and I think it's a case of "The code says you can't put angle fitting in the wall so it's a violation"


George Little

#96158 - 11/07/05 12:40 PM Re: Flexible Metal Conduit  
Alan Nadon  Offline
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Joined: Mar 2005
Posts: 399
Elkhart, IN. USA
George,
The 90' connector is not allowed for the reasons others have already listed.

My problem is why are you letting anyone put a junction box in a cold air return ???

300.22 (C) Exception; is in the book because a stud or joist space is NOT other space but is a duct or plenum covered by part (B)
Alan--Inspector

[This message has been edited by Alan Nadon (edited 11-07-2005).]


Alan--
If it was easy, anyone could do it.

#96159 - 11/07/05 01:06 PM Re: Flexible Metal Conduit  
raider1  Offline
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Joined: Jul 2005
Posts: 46
north logan, utah, US
Alan,

I believe that George is right about the joist space as being "Other space used for enviromental air."

The joist space is not a duct or plenum.

The definition of Plenum in the NEC says "A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system."

To me the cold air return is not part of the air distribution system.

JMO, Chris


#96160 - 11/07/05 05:47 PM Re: Flexible Metal Conduit  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
Alan- I think I indicated that it was a device box, not a junction box. Really makes no difference as long as it is accessible. In the case stated the wall space required a receptacle and the CA was covering several stud spaces and the receptacle was located in the CA. You also have situations where a switch ends up in the CA. I do not see a problem with using an angle connector for this type of installation and would approve it. No one has offered any reason to require a straight connector because the wire will most likely be removed.


George Little

#96161 - 11/07/05 07:04 PM Re: Flexible Metal Conduit  
Alan Nadon  Offline
Member
Joined: Mar 2005
Posts: 399
Elkhart, IN. USA
Got to disagree.
That is why I have two titles:
Inspector & SOB. I think the second one is something about Same Old...
First, stud and joist spaces are connected to the plenum / duct system and are definately part of the 300.22(B) space. If you check the exception to 300.22 (C) the reason for the exception is because it is not to be considered anything other than a duct as covered by 300.22 (B)
Regular NM cable is allowed to run across a space in 300.22 (B). It is done all the time.
NM cable is not allowed to run the length of a 300.22 (B) space nor is a junction or device box allowed in that space unless designed for use in a duct or plenum.
The other space 300.22 (C) is for above ceiling areas and rooms that may have furnaces in them because some inspectors did not allow a return air grill on a furnace unless the entire room was wired as a plenum. That was overkill.
I do not allow any [except dust tight] junction boxes or device boxes in the stud or joist space used for return air. They trap dust and dirt in the boxes.
To solve the problem have the electrician {carpenter} put a length of 2X4 where the box is, from top to bottom with the top & bottom closed off and forget about any metal sleeveing on the cable. That way the box is no longer in the plenum / duct space.
Do not accept the tin foil cardboard as a substitute for the 2X4 as a way of getting the box out of the duct. The drywall can seal against the 2X4 with nails, the cardboard can not.
The 90' connector is still a violation, NM cable or not.
HVAC guys get it messed up all the time. One even insist that he always runs his thermostat wire inside the duct to get to the upstairs.
I have seen dust and dirt in boxes that resulted in fires.
Have your Code Panel respond to this at the next IAEI meeting. Or just ask Joe T.
Alan-- Inspector--
CEI-M #138 listed in the IAEI NEWS


Alan--
If it was easy, anyone could do it.

#96162 - 11/07/05 07:33 PM Re: Flexible Metal Conduit  
raider1  Offline
Member
Joined: Jul 2005
Posts: 46
north logan, utah, US
Alan,

If you classify a stud space as a duct or plenum, as per 300.22(B) then the exception for part (C) would not apply, and you could not install NM cable in that space at all.

As for a device box in the space I agree that it can not be installed in the cold air return. Also the 90% flex fitting is a violation because it is not accessible.

Chris


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