Weather tight

[ebservicesllc]

On a NEMA 3R disconnect with concentric knock-outs; is it required by code to install a Myers hub?

 

[augie47]

Depends on where you enter the enclosure. See 312.2
(If you enter through a knockout, one should not be needed)

 

[btharmy]

Have never seen a 3r disconnect with a concentric knockout on the top. Only place, in my opinion, that would require a meyers hub anyway.

 

[Cavie]

There is no requirement to use a Myers hub anywhere in the NEC.

 

[don_resqcapt19]

With a 3R enclosure and using the knockouts, there is no code reason to use anything other than locknuts and bushing.

 

[Rockyd]

A sealing locknut would be the bare bone minimum I can see using on the side of a 3R box. Assuning a 3R box was used because of environment. Locknuts are not rated for such an environment. A Sealing Locknut is and normally used if coming the side of a box. Myers hubs are great for treaded pipe as long as the top is smooth and no rings. After the choir read in on Meyers hubs back around Halloween....

I think 312.2 and 314.15 will support my position.

 

[hurk27]

A sealing locknut would be the bare bone minimum I can see using on the side of a 3R box. Assuning a 3R box was used because of environment. Locknuts are not rated for such an environment. A Sealing Locknut is and normally used if coming the side of a box. Myers hubs are great for treaded pipe as long as the top is smooth and no rings. After the choir read in on Meyers hubs back around Halloween....

I think 312.2 and 314.15 will support my position.

I dont read 312.2 that way:

I. Installation​

312.2 Damp and Wet Locations.

In damp or wet locations,

surface-type enclosures within the scope of this article
shall be placed or equipped so as to prevent moisture
or water from entering and accumulating within the cabinet
or cutout box, and shall be mounted so there is at least
6-mm (​

​

1⁄4-in.) airspace between the enclosure and the wall

or other supporting surface. Enclosures installed in wet locations
shall be weatherproof. For enclosures in wet locations,
raceways or cables entering above the level of uninsulated​

live parts shall use fittings listed for wet locations.
​

Above in red say's "Above" not below
​

 

[Dennis Alwon]

I agree with Wayne. The sealing locknuts are not required below the busbar.

Here is something from the white book that will drive you nuts-- same is true for myers hubs

Sealing (Liquid-tight) Locknuts — Sealing locknuts are intended for use with threaded rigid metal conduit and intermediate metal conduit with one sealing locknut in the outside or the inside and either an ordinary locknut or sealing locknut on the inside of the enclosure for wet locations or liquid-tight applications. Sealing locknuts may also be used with Listed wet location or liquid-tight fittings where so marked on the fitting carton and used on the inside of the enclosure.

 

[Dennis Alwon]

I also found this from Carlon for PVC.