nm-b cable feeding exterior ac disconnect

[jsherwin]

I am new to the forum and cannot seem to find a definitive answer to this - but rather a lot of opinions. Can you use nm-b cable to feed an exterior ac disconnect that is mounted to a wall? I live in Florida and on any given residential construction site you can find nmb cable hanging out of a wall and the ac guy just mounts a disco over it. Are all of these installations in violation? Can anyone cite and article that makes this "ok". Also, is it legal to feed any box located on an exterior wall with nmb from the interior? Thank you.

 

[infinity]

Yes it's permissible and that's how just about every outdoor AC disco, receptacle and lighting fixture are fed in most of the country.

Welcome to the Forum.

 

[GoldDigger]

On the other hand, if somebody put the hole through the wall in the wrong place and you run a raceway (conduit, EMT, surface mount....) from the hole to the place you put the disconnect, you cannot use NM inside that exterior raceway.

 

[jsherwin]

Yes it's permissible and that's how just about every outdoor AC disco, receptacle and lighting fixture are fed in most of the country.

Welcome to the Forum.

Thank you Rob.
Can anyone give a specific code citation of why this is acceptable? Is it that the enclosure would need to be rated nema 3r and thereby be "dry" - as opposed to "wet" which is not allowed with nmb cable?

Also, (which prompted this question in the first place, but I needed a common example of nmb terminating in a box) if you have a pv system micro-inverter output (ac) on a roof and went into a nema 3r enclosure and then connected to nmb cable coming from attic, would this be the same?

Thank you.

 

[JFletcher]

I am new to the forum and cannot seem to find a definitive answer to this - but rather a lot of opinions. Can you use nm-b cable to feed an exterior ac disconnect that is mounted to a wall? I live in Florida and on any given residential construction site you can find nmb cable hanging out of a wall and the ac guy just mounts a disco over it. Are all of these installations in violation? Can anyone cite and article that makes this "ok". Also, is it legal to feed any box located on an exterior wall with nmb from the interior? Thank you.

Welcome. Yes. No, and no I can't. Last question: in resi, I havent seen an exception that wouldnt otherwise apply in a jurisdiction (Chicago, for example).

Those outdoor discos will get water in them if the NM comes in from the back, simple as that. Even if NM is legal, leaving off the connector on the NM to the disco is a common violation that no one ever seems to get gigged on.

 

[jap]

I thought there was a thread a while back that said this was a violations since the NM was not rated for a wet location and the area between where it came out of the wall to the back of the disconnect was just that regardless of how small the gap.

JAP>

 

[GoldDigger]

I thought there was a thread a while back that said this was a violations since the NM was not rated for a wet location and the area between where it came out of the wall to the back of the disconnect was just that regardless of how small the gap.

JAP>

That argument was brought up in a pretty lengthy thread, but I would not go so far as to say that the consensus of the thread was that it was against code.
IIRC the majority of those who felt the code technically prohibited such use still felt that it was safe and commonly used. And nobody reported an AHJ who tagged such a use.

 

[jap]

That argument was brought up in a pretty lengthy thread, but I would not go so far as to say that the consensus of the thread was that it was against code.
IIRC the majority of those who felt the code technically prohibited such use still felt that it was safe and commonly used. And nobody reported an AHJ who tagged such a use.

Sounds good.
One less thing to worry about.

JAP>

 

[GoldDigger]

Sounds good.
One less thing to worry about.

JAP>

I think that the other point made was that the designation of the inside of an outdoor raceway as a wet area does not explicitly apply to an enclosure, and it is not at all given that a raceway going into the back of a flush mounted box is outside.
With a surface mounted enclosure like a typical disconnect, it is at least arguable.
If there is an NM fitting and no raceway, it is even less plausible that it is prohibited by code.

 

[peter d]

I am new to the forum and cannot seem to find a definitive answer to this - but rather a lot of opinions. Can you use nm-b cable to feed an exterior ac disconnect that is mounted to a wall? I live in Florida and on any given residential construction site you can find nmb cable hanging out of a wall and the ac guy just mounts a disco over it.

I'm sure the a/c guy goes a good job of wiring it too. :happyno:

 

[JFletcher]

I'm sure the a/c guy goes a good job of wiring it too. :happyno:

AC guy could mount the disco just like siding guys mount the siding blocks for lights, tho I'd prefer to mount the disco myself, and wire both ofc. If the AC guy damaged my cable wiring the disco, or did anything incorrect in there, it would be on my permit, and I'd eat the $50 re-inspection fee, or the callback because it isnt working.

 

[iwire]

Can anyone give a specific code citation of why this is acceptable?

We need to look it the other direction, what code prohibits it?

Is it that the enclosure would need to be rated nema 3r and thereby be "dry" - as opposed to "wet" which is not allowed with nmb cable?

In my opinion that is the key.

To me it would make no sense to call the inside of enclosure that might contain breakers, fuses, or even the electronics of an inverter 'dry' for those items but 'wet' when it comes to the NM entering it.