Romex clamp and Bell box

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abrace

Member
Location
New Hampshire
Occupation
Telecommunications Engineering
All,

Code technicality question.

We have all either done it or seen it done. A bell box mounted to the outside of a structure fed from the back with Romex secured by a Romex clamp, without locknut, threaded into the female threads in the back of the bell box. Question is, does this technically pass code? I haven't seen it done any other way in residential, but with all the straight threads vs tapered and discussions around using short RMC nipples for transitions, it got me wondering.

---Aaron
 

abrace

Member
Location
New Hampshire
Occupation
Telecommunications Engineering
can romex be used outside?

No, it cannot, but these are bell boxes mounted directly to an exterior wall, the romex is run in said wall and terminated directly into the back of the bell box.

I know all about the UF/NM arguments regarding whether or not once the wire enters the back of the bell box it is considered a wet location. Not looking to rehash that argument here.

---Aaron
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
No, it cannot, but these are bell boxes mounted directly to an exterior wall, the romex is run in said wall and terminated directly into the back of the bell box.

I know all about the UF/NM arguments regarding whether or not once the wire enters the back of the bell box it is considered a wet location. Not looking to rehash that argument here.

---Aaron


That is compliant. If it weren't then there would be an issue with all the nm that comes into an exterior panel. NM run in a raceway is a wet location but inside the panel is not considered a raceway.
 

abrace

Member
Location
New Hampshire
Occupation
Telecommunications Engineering
That is compliant. If it weren't then there would be an issue with all the nm that comes into an exterior panel. NM run in a raceway is a wet location but inside the panel is not considered a raceway.

Agreed, my question was actually regarding threading a romex clamp into a female threaded bell box and the compliance of that.

---Aaron
 

MHElectric

Member
Location
NC
I used to just fly into the back of a bell box with no connector at all. Then I repented for my sinful ways.

Now I use a 1/2" chase nipple.
 

tkb

Senior Member
Location
MA
The romex connector is not used for grounding so the straight vs tapered threads shouldn't apply.
 

kwired

Electron manager
Location
NE Nebraska
If the OP concern is the straight vs tapered thread - there is a lot of straight threaded raceway fittings threaded into this type of box out there as well, I have little concern over the NM cable clamp, only slight concern over other raceway fittings - enough to forget about it by the time I run another such fitting into another bell box;) Probably will be doing that many times in the next couple months as well.
 

infinity

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Staff member
Location
New Jersey
Occupation
Journeyman Electrician
The romex connector is not used for grounding so the straight vs tapered threads shouldn't apply.

I agree, the straight v. tapered argument involves grounding, but can anything other than RMC or IMC be compliantly threaded into a hub according to UL?
 

abrace

Member
Location
New Hampshire
Occupation
Telecommunications Engineering
I agree, the straight v. tapered argument involves grounding, but can anything other than RMC or IMC be compliantly threaded into a hub according to UL?

Exactly my question. The romex clamp in the back of a bell box is just an example that can probably be found in the majority of residential construction in my area.
 

kwired

Electron manager
Location
NE Nebraska
Exactly my question. The romex clamp in the back of a bell box is just an example that can probably be found in the majority of residential construction in my area.
So your choices are to either do what most others do and use the NM connector or do what you think is the right thing and feed those boxes with RMC or IMC - and price yourself out of doing a lot of those jobs as well.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Exactly my question. The romex clamp in the back of a bell box is just an example that can probably be found in the majority of residential construction in my area.

Just about anything other than RMC or IMC screwed into a hub is a violation and that includes EMT connectors, SE cable connectors, PVC terminal Connectors, MC connectors, NM connectors, etc. Having said that I wouldn't worry about an NM connector in a hub.

In answer to the question in the OP is it a technical violation, the answer is yes.
 

Smart $

Esteemed Member
Location
Ohio
Let's try to clear one thing up. As far as Code goes, a hub is not the same as a threaded entry. If a product is UL listed and has integral threaded entries, you have to verify whether it is or isn't an integral hub. Typically, an integral hub will have about 3/4" to 1" of tapered threads, which pretty much yells, "I am for RMC/IMC.". Threaded entries which only have a few threads, usually only the thickness of the enclosure, box, cabinet, etc., can be used for any type of connector IMO. I haven't really searched for authoritative documentation to that effect because I am satisfied with my belief.... :happyyes:


FWIW, compare an FS/FD box threads with those of a bell box.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Let's try to clear one thing up. As far as Code goes, a hub is not the same as a threaded entry. If a product is UL listed and has integral threaded entries, you have to verify whether it is or isn't an integral hub. Typically, an integral hub will have about 3/4" to 1" of tapered threads, which pretty much yells, "I am for RMC/IMC.". Threaded entries which only have a few threads, usually only the thickness of the enclosure, box, cabinet, etc., can be used for any type of connector IMO. I haven't really searched for authoritative documentation to that effect because I am satisfied with my belief.... :happyyes:


FWIW, compare an FS/FD box threads with those of a bell box.

But UL says connectors have not been evaluated for use with anything other than lock nuts, so it doesn't matter is it is a hub or a threaded entry that you want to use the connector with. Note that saying they have not been evaluated for a use is not the same as saying they can't be used for that use.
 
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