"wet" location fittings and conduit

[rszimm]

Running conduit outdoors has always been a bit of a mystery to me as to which fittings are required. So let's limit this to a typical outdoor setting where the conduit is likely to come in contact with rain (e.g. not underground or in a car wash or anything like that). So, 312.2 states "For enclosures in wet locations, raceways or cables entering above the level of uninsulated live parts shall use fittings listed for wet locations", implying that if you're entering below those parts, you don't need wet location fittings. However 314.15 states "Boxes, conduit bodies, outlet box hoods, and fittings installed in wet locations shall be listed for use in wet locations". So, if i use the standard knockouts at the lower half of a breaker box/meter box/disconnect/etc, do I need to use wet fittings or not? 314.15 seems to say "yes". 312.2 seems to say "no".

Second question. In this same "wet" environment are threaded rigid connections sufficiently waterproof? I.e. if I had two threaded conduit bodies a few inches from one another and ran a threaded rigid nipple between them, wrench tight, no lock-nuts, is that OK? Do I need to put pipe-dope on them to seal? Maybe a sealing lock-nut?

Final question. When running into a breaker box with a rigid nipple, my understand is I need a regular locknut on the outside and a bonded one on the inside whenever I use a factory knockout toward the bottom of the enclosure, but I need a sealing locknut on the outside and a regular locknut on the inside if I drill a hole toward the top of the box. Correct?

Again, always been confused by this in the past and usually just throw a bunch of sealing locknuts all over the place and always use "wet location" fittings

 

[infinity]

Meter enclosures and panels are not the same as boxes. For boxes all entries need to be rated for wet locations when in wet locations for the other two they do not need to be rated for wet locations if they enter below the live parts.

 

[Carultch]

Meter enclosures and panels are not the same as boxes. For boxes all entries need to be rated for wet locations when in wet locations for the other two they do not need to be rated for wet locations if they enter below the live parts.

I take it that by "box", you mean an enclosure that is initially empty, as opposed to the housing for manufactured equipment. Pull box, junction box, wire trough, etc.

What about equipment that is neither a "box", nor a meter/panelboard/disconnect?

 

[infinity]

The OP mentioned Article 312 and 314 boxes are covered under 314 and have different requirements than the cabinets and enclosures covered under 312.

 

[Nuber]

The main question is caused by the maddening circular reasoning found in the NEC (in my humble opinion).

NEC 358 requires EMT fittings when installed in wet locations to conform with NEC 314. Therefore when EMT is installed in wet locations; listed, wet location couplings and connectors are required when connected to article 314 items and are not when installed to an article 312 item.

Per NEC 344 GRC only has the above fitting requirement for threadless fittings. Therefore when GRC is installed in wet locations to any 312 or 314 item requires standard locknuts and/or threaded makeup only unless threadless fittings are used.

However per 312 any installation made above the energized bus requires listed wet location fittings regardless of the other rules.

Soooo... When you install two 10' sticks of EMT in a wet location between an LB (article 314 item) on one end and an electrical panel (article 312 item) below the bus on the other what is the required rating of the coupling in the middle?

 

[rszimm]

So think you guys have clarified (and muddied) the issues here. Seems like it's best practice to just treat everything exposed to rain as a wet location fitting. 312.2 seems to provide an exeption for going into a cabinet/meter socket below the equipment, but I won't go wrong just throwing a wet location fitting there.

However, I'm still unclear if rigid threaded couplings are appropriate for this location? 344 doesn't give a whole lot of insight. If I run a rigid threaded conduit or nipple into a threaded conduit body and wrench tighten it, am I good? Do I have to put a sealing locknut on it? Can I use pipe-dope?

 

[rbalex]

...
However, I'm still unclear if rigid threaded couplings are appropriate for this location? 344 doesn't give a whole lot of insight. If I run a rigid threaded conduit or nipple into a threaded conduit body and wrench tighten it, am I good? Do I have to put a sealing locknut on it? Can I use pipe-dope?

(This comment is limited to common galvanized RMC.) I believe Article 344 gives plenty of insight; especially Section 344.10(A)(1).

 

[Carultch]

(This comment is limited to common galvanized RMC.) I believe Article 344 gives plenty of insight; especially Section 344.10(A)(1).

3-piece and threadless RMC couplings need a listed wet location rating or raintight rating, if installed in a wet location.

Standard RMC couplings carry this by design when used with RMC or IMC, as the male threads of the pipe are tapered, which provides the waterproofing for negligible pipe pressure. Tapered couplings are needed for plumbing pipe, but tapered male conduit in straight female couplings, are acceptable when leak potential is not driven by a pressurized pipe.

334.10(B) says elbows, couplings, and fittings shall be permitted in direct contact with the earth (which is a wet location).
344.42 says that threadless products are a special case, requiring the product documentation to specify wet locations.

The one thing that is not acceptable, unless listed otherwise, is mixing straight thread components. Straight male threads need to terminate on enclosures with a locknut, and not on straight female thread components (hubs, couplings, embedded thread entries, etc).

 

[infinity]

1)-So think you guys have clarified (and muddied) the issues here. Seems like it's best practice to just treat everything exposed to rain as a wet location fitting. 312.2 seems to provide an exeption for going into a cabinet/meter socket below the equipment, but I won't go wrong just throwing a wet location fitting there.

2)-However, I'm still unclear if rigid threaded couplings are appropriate for this location? 344 doesn't give a whole lot of insight. If I run a rigid threaded conduit or nipple into a threaded conduit body and wrench tighten it, am I good? Do I have to put a sealing locknut on it? Can I use pipe-dope?

1-Yes.

2-RMC couplings are fine in wet locations and no you do not want to use anything that will diminish the metal to metal connection at the coupling. If you're concerned about the coupling leaking then you can seal it from the outside after installation.

 

[Carultch]

1-Yes.

2-RMC couplings are fine in wet locations and no you do not want to use anything that will diminish the metal to metal connection at the coupling. If you're concerned about the coupling leaking then you can seal it from the outside after installation.

I had a project where the installers lost the gaskets that come with LFMC connectors, which were being threaded in to RMC couplings. They improvised and wrapped the threads with teflon tape. That may seal the threads, but now you loose your ground continuity.

Turns out, you aren't supposed to do this anyway. Should be using combination couplings, instead of threading a connector in to a coupling.

 

[Clodbuster]

For the conduit threads, I use Kopr-Shield if it's exposed to moisture. As far as water is concerned, it is a thread sealant that will keep it out. Unlike plumber's pipe dope it won't degrade continuity - it will enhance it if anything. Though I've never used it to coat conductor ends before terminating like it says on the bottle - anyone else done that?

I put it on all the threaded parts exposed to wet conditions, but I'm pretty sure most electricians (here) consider it a waste of time. Pretty sure because when I asked at the supply house they said that they only sell a bottle once in a rare while, when it is called for by spec.

Also, just like pipe dope, it will get on EVERYTHING. I take time to wipe excess off the visible runs... which is probably another reason why guys don't use it.