Can I come thru a wall into the back of a NEMA 3R enclosure mounted on the wall and maintain the 3R rating?

Thanks

If you use a myers hub.

To answer that, you need to understand how the enclosures are tested.

For the NEMA-3R test, a driving rain is sent onto the enclosure at about a 15 degree angle. At the end of the test, there cannot be a 'significant' amount of water in the enclosure.

In addition, there is a rule that factory KO 'pre-punches' cannot be located higher than the lowest energized part.

Some understand the latter rule to mean that ANY opening made above the lowest energized part has use a Myers' hub. I'm not convinced of that logic for vertical faces, though I agree when the opening is on the top face. (After all, snow and water can accumulate on the top).

For openings on protected faces - like the back - I have a bit of trouble imagining how any significant amount of water can ever reach the opening - let alone enter it.

Remember ... NEMA-3R is essentially a glorified umbrella; it's not intended to protect a directed water source, such as a hose stream.

I agree with Reno. The hole on top of some 3R's enclosures has that up rolled lip to prevent wat to get into the enclosure.

Don't we go in the back of meter cans all the time? I don't remember any special fitting.

The special fittings were for "field expediant" holes not factory KO's

You can use a nipple or conduit in the back bottom factory KO and maintain the rating. If its a concentric KO, and you have any rings left you must bond with a bonding bushing. Not required with PVC of course.

JV, Unless it's service equipment (or you really blow out the concentric KO's), they're not required on systems for under 250 volts to ground.