NM cable and the outdoors
- Thread starter JoeNorm
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
It is not compliant unless you live in NC where we have an amendment that allows 6' for that purpose and for ac units.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
For outdoor equipment, like disconnects or even exterior panels, it has always been allowed.
IMO, if its in a box or enclosure rated for outdoor use, the interior of the enclosure should stay dry, and NM should would be allowed.
It would NOT be allowed inside outdoor conduit or flex or sealtight (unless you are in NC) because the interior of conduits in a wet location is also considered to be a wet location due to condensation among other things.
It would NOT be allowed inside outdoor conduit or flex or sealtight (unless you are in NC) because the interior of conduits in a wet location is also considered to be a wet location due to condensation among other things.
I think its a technical violation, but most places let you do it. An outdoor disconnect usually has little rises on the mounting holes to keep the box 1/4" off the mounting surface. That 1/4" gap needs to be jumped when wiring from the inside goes into the back of the disconnect. That 1/4" jump is a wet or damp area whether an NM clamp is there or you use a conduit nipple. But I think not allowing NM for that is being overly picky.
- Location
- Illinois
- Occupation
- retired electrician
Parts of the interiors of 3R enclosures get wet...such enclosures are required to have drain holes per the product standard.
At an IAEI CEU class about 2 years ago this was brought up. Instructor stated that cable type NMB is not approved for damp or outdoor locations so it would not be allowed. Been using romex for last 50 years for outdoor wall luminares on homes without any problem. My mom's house was built in the 1950's with cloth covered romex. I just replaced her outdoor wall luminare and cloth covered romex wire appeared to have no problems. I would apply silicone around end of plastic romex jacket and seal cable & box to prevent condensation due to temperature difference.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I don't believe installing NM inside a wall for an outdoor lamp is the issue they are talking about. The issue is nm running outside the walls in a conduit. If wiring to an wall light was an issue then every outdoor panel would be a violation also.
I agree that nm in a conduit esp. in a vertical run from a crawl to an outdoor panel is not a safety issue. It is however, not compliant by the NEC.
OK, so it sounds like it makes a difference if we have a NEMA 3R enclosure, or something more water tight like a gasketed box for an outdoor wall luminare?
Nuber
State Certified Practitioner of Electrical Arts
- Location
- Colorado
- Occupation
- Master Electrician
My rationale - if you like to over analyze such things.
NM is prohibited from use wet or damp locations 334.12(B)(4). All underground exterior raceways are considered to be a wet location therefore no NM is allowed underground, ever 300.5(B). This is not the same as a raceway on the side of a building.
However, a recessed box in a wall is never considered a wet location or a damp location. Whatever covers the box seals it from the elements when properly installed so as to make the interior of a recessed box a dry location. NM is code compliant inside such a box. 314.15
Once the box, cabinet, cutout box, meter enclosure, etc. is surface mounted outdoors, then it is either a damp or a wet location depending on the circumstance of location. However the interior of such a box is considered a dry location if properly installed and covered. NM is code compliant inside such a box. 314.15
All raceways on the surface of a building must be listed or approved for the installation. 225.22 There is no code that I can find that calls the interior of a raceway installed on the side of a building a wet location. If such a raceway is itself listed or approved for wet or damp locations, then the interior of such a raceway is considered a dry location. In such a scenario I suggest that NM is allowed.
Examples -
Raintite fittings installed with EMT from bell box to bell box on the outside wall of a house without an eave or porch. Wet location by definition, wet location rated raceway, inside the EMT is a dry location, NM is allowed (as would THHN).
Same as above except with compression fittings, listing of those fittings makes the interior of the EMT a damp location, NM is prohibited. A damp location wiring method inside the raceway such as NMC or THWN would be required.
The kicker, and what inspectors seem to have an interpretation position for, is the requirement for the raceway to be "arranged to drain" and "approved". In my first example, is the raceway if installed horizontally considered to be "arranged to drain"? If not, then all horizontal raceways fail to be code compliant in the first place. Can a person drill a 1/8" hole in the bottom of a horizontal run of 1/2" EMT and become compliant? Such an install concept is found in the fine prints notes under 225.22 but is not code enforceable.
For me - I don't want to have an install be open to interpretation by some young buck inspector who is full of beans and wants to flash his knowledge around. As such, I never install NM in a wet or damp location regardless of the raceway. I will install NM inside of any box in a wet or damp location that is itself properly installed. And I train my crews accordingly.
I have no problems to report with my methods.
NM is prohibited from use wet or damp locations 334.12(B)(4). All underground exterior raceways are considered to be a wet location therefore no NM is allowed underground, ever 300.5(B). This is not the same as a raceway on the side of a building.
However, a recessed box in a wall is never considered a wet location or a damp location. Whatever covers the box seals it from the elements when properly installed so as to make the interior of a recessed box a dry location. NM is code compliant inside such a box. 314.15
Once the box, cabinet, cutout box, meter enclosure, etc. is surface mounted outdoors, then it is either a damp or a wet location depending on the circumstance of location. However the interior of such a box is considered a dry location if properly installed and covered. NM is code compliant inside such a box. 314.15
All raceways on the surface of a building must be listed or approved for the installation. 225.22 There is no code that I can find that calls the interior of a raceway installed on the side of a building a wet location. If such a raceway is itself listed or approved for wet or damp locations, then the interior of such a raceway is considered a dry location. In such a scenario I suggest that NM is allowed.
Examples -
Raintite fittings installed with EMT from bell box to bell box on the outside wall of a house without an eave or porch. Wet location by definition, wet location rated raceway, inside the EMT is a dry location, NM is allowed (as would THHN).
Same as above except with compression fittings, listing of those fittings makes the interior of the EMT a damp location, NM is prohibited. A damp location wiring method inside the raceway such as NMC or THWN would be required.
The kicker, and what inspectors seem to have an interpretation position for, is the requirement for the raceway to be "arranged to drain" and "approved". In my first example, is the raceway if installed horizontally considered to be "arranged to drain"? If not, then all horizontal raceways fail to be code compliant in the first place. Can a person drill a 1/8" hole in the bottom of a horizontal run of 1/2" EMT and become compliant? Such an install concept is found in the fine prints notes under 225.22 but is not code enforceable.
For me - I don't want to have an install be open to interpretation by some young buck inspector who is full of beans and wants to flash his knowledge around. As such, I never install NM in a wet or damp location regardless of the raceway. I will install NM inside of any box in a wet or damp location that is itself properly installed. And I train my crews accordingly.
I have no problems to report with my methods.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Methinks that's incorrect.
- Location
- Illinois
- Occupation
- retired electrician
bkludecke
Senior Member
- Location
- Big Bear Lake, CA
- Occupation
- Retired Electrical Contractor
300.9
Eddie702
Licensed Electrician
- Location
- Western Massachusetts
- Occupation
- Electrician
A lot of people think straight THHN is ok outdoors. I know that most all of it is dual listed now. Gotta have a W in it
I agree with the NM cable and the THHN conductors not allowed in wet location, and the AHJ has every right to dissect the OP installation and decide whether or not it is compliant.
But, there is always a but, IMO this is what happens when manufacturer greedy reps get involved with the CMP. and push different product in place of the existing one that has been working well over 30 years without any issues.
Like the NM cable that has been fine for outdoors for many years and now (well it is has been for a while) it is a hazard. I guess if I was the manufacturer I may do the same thing because it is about the Benjamins.
It could also be that the manufacturing process and material that was available 30 years ago that allowed construction of the NM cable is not available anymore, hence the new product and the NEC change. I don't know.
But, there is always a but, IMO this is what happens when manufacturer greedy reps get involved with the CMP. and push different product in place of the existing one that has been working well over 30 years without any issues.
Like the NM cable that has been fine for outdoors for many years and now (well it is has been for a while) it is a hazard. I guess if I was the manufacturer I may do the same thing because it is about the Benjamins.
It could also be that the manufacturing process and material that was available 30 years ago that allowed construction of the NM cable is not available anymore, hence the new product and the NEC change. I don't know.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Personally I think it's fine to bring NM through an exterior wall so long as it comes immediately into a box where it it's spliced to transition to another wiring method. Doesn't matter if the box is recessed or not. Boxes are not wiring methods. One could quibble and argue the exact wording, to be sure, but the argument against is not that reasonable. In my opinion.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Not true. Some places will not allow a panel on the outside of a house because there is no way to bring the NM home runs into it that satisfies the Code.
-Hal
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Wouldn't splicing to a suitable wiring method satisfy that?
- Status