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#180482 08/27/08 03:25 PM
Joined: Apr 2002
Posts: 32
S
sudsy4 Offline OP
Member
Can I come thru a wall into the back of a NEMA 3R enclosure mounted on the wall and maintain the 3R rating?

Thanks


Bill
Joined: Jul 2007
Posts: 265
W
Member
If you use a myers hub.


Jimmy

Life is tough, Life is tougher when you are stupid
Joined: Jan 2005
Posts: 5,316
Cat Servant
Member
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.

Joined: Jul 2007
Posts: 1,335
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Member
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.


"Live Awesome!" - Kevin Carosa
Joined: Jul 2004
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G
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Don't we go in the back of meter cans all the time? I don't remember any special fitting.


Greg Fretwell
Joined: Jul 2007
Posts: 1,335
S
Member
The special fittings were for "field expediant" holes not factory KO's


"Live Awesome!" - Kevin Carosa
Joined: Jun 2007
Posts: 301
J
Member
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.

Joined: Dec 2000
Posts: 4,287
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Quote
If its a concentric KO, and you have any rings left you must bond with a bonding bushing


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.



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