NEMA12 to NEMA3R/4 Retrofit Needs 1

[CtrlSystemsEng]

We have an air compressor that is presently in a NEMA 12 enclosure. We need to move it to the outside pad and it will therefore require the enclosure to be NEMA 3R or 4. Anyone have any experience with enclosure retrofit kit options or other suggestions. Trying to avoid a wholesale repackaging of the entire unit. Thanks.

 

[DRWeig]

Hi CtrlSystemsEng,

Not sure how you'd go about getting an enclosure manufacturer to send you a new label, but most NEMA 12 enclosures are already 3R if you add a drain hole in the bottom (below the level of the lowest energized conductor).

For example, many Hoffman NEMA 12 enclosures and Square D enclosed starters come with an instruction sticker on the inside of the door. It tells you to drill a hole in the bottom for NEMA 3R applications.

Check with your enclosure manufacturer and see!

Good on ya,

Goober Dave

 

[jraef]

Not really, that's a common misunderstanding. They tell you how to modify the enclosure to make it "raintight", but if you look carefully, they never actually use the term "UL Type 3R" because UL does not allow the rating to be determined by the skill of the installer. Type 3R also has some painting and salt spray withstand specifications for outdoor use that are not part of the Type 12 test standards. Unfortunately, that Type 12 enclosure will have a sticker on the inside that very clearly states "Indoor use" because of this. Most savvy inspectors will reject it simply for that reason. Sometimes you get lucky though...

Some newer enclosures bear a Type 4/12 rating, and type 4 is rated for outdoor use, but is still not technically Type 3R because of the internal condensation issue and as soon as you drill a weep hole, it is technically no longer Type 4 either. It's a conundrum that has burned many a contractor if you get an inspector that knows the issues correctly.

Chances are there is a corresponding Type 4 enclosure the exact same size as the one you have that will use the exact same back panel(s), so you may need to only change out the outer box, not rebuild the entire thing. You can also go the route of asking your AHJ ahead of time if they will accept a modified Type 12 enclosure. If they will, then Hoffman and their competitors all sell what is called a "Drip Shield Kit" that will go on the outside of the upper lip, then the only other thing you need is a stainless steel hing pin and a weep hole in the bottom to allow condensation to drain.


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