Modifying Nema 4 enclosure

[fifty60]

If I add NEMA 3R vents to a NEMA 4 enclosure, is the overall enclosure now rated at NEMA 3R?

I remember reading somewhere earlier that the rating took the lowest rating on the enclosure. I cannot find information to back that up now, however.

You would have a better protected enclosure for outdoors if the entire enclosure was rated 4, with 3R vents, than you would with a 3R enclosure with 3R vents...in my opinion. Nema 3R is acceptable in my application.

I find the exact dimensioned enclosure I am looking for in Nema 4, however, that is why I want to buy the Nema 4 and ventilate it making it 3R

 

[Jraef]

Whenever you do ANYTHING to an enclosure, including conduit penetrations, you are technically voiding it's UL environmental listing. The listing is only good as a box with nothing done to the outside of it. But if WHAT you do meets the requirements of the same UL Type, you can maintain that rating for the NEW package of enclosure + device / penetration method. So for example if you have a Type 3R box and you come into the top with a standard conduit penetration, you are no longer Type 3R. But if you use a Type 3R listed hub assembly, that combination is fine, because everything is being used as intended.

Nothing you can do, or not do, CHANGES that rating to some OTHER rating however. If a box is made, tested and listed as UL Type 4, it is UL Type 4 and nothing else (unless specifically listed that way). So if the box is made to UL type 4 and you add something that is rated for Type 3R, you have no rating whatsoever.

That however does not mean you can't use it. Any decent AHJ worth a damn would know that your intent would be "outdoor use" if you started with a UL Type 4 enclosure (which includes outdoor use) and added UL Type 3R accessories to it. You just can't CLAIM that the box meets a UL Type spec that it has not been tested and listed for.

And for the record, UL Type 3R has spec elements to it that a UL Type 4 does not provide, chiefly that there is a degree of protection from falling rain when the door is open. Type 4 makes no allowance for that, it is STRICTLY a closed door spec.

 

[LMAO]

If I add NEMA 3R vents to a NEMA 4 enclosure, is the overall enclosure now rated at NEMA 3R?.....

yes

 

[ggunn]

yes

It may meet NEMA 3R standards functionally but it it will no longer have a NEMA 4 or 3R listing. Whoever made the box will not stand behind his field modification unless it's published as an acceptable mod.

 

[LMAO]

It may meet NEMA 3R standards functionally but it it will no longer have a NEMA 4 or 3R listing. Whoever made the box will not stand behind his field modification unless it's published as an acceptable mod.

OP made no mention of "UL". You can have an enclosure that conforms to NEMA3R but is not UL listed. I assume OP is familiar with UL standards.

 

[petersonra]

It is more complicated than that. UL 508a specifically allows for modifications to standard listed enclosures that result in an enclosure that has a "lesser" rating.

My understanding is that these modifications are somehow referenced or included in the UL enclosure standards so technically they are part of the listing of the enclosure and thus you can make the specified changes to a listed enclosure and come out with an enclosure with a lesser rating if you follow the rules.

 

[fifty60]

Very interesting. I will take a look at UL 508A for future reference regarding modifying NEMA (brought to you by UL) rated enclosures. For this application, the UL (I really want to only mean NEMA, but I guess that is impossible now) are not important, or at least, are not required.

It is a 30X36 NEMA 4 enclosure. I will add the NEMA 3R ventilation system, but will "doghouse" the overall modified enclosure inside a larger vented enclosure. The vents are offset in a way that will hopefully prevent any driven rain/snow from entering the enclosure.

I will also add a 200W heater to the enclosure to hopefully help with condensation and also keep the enclosure above freezing.

 

[kwired]

Instructions for a NEMA 12 panelboard cabinet I have installed frequently say to remove the drain screws in the bottom of the cabinet for NEMA 3R applications. I would assume if the screws are removed it is now a 3R cabinet. It is identified in the catalog as NEMA 3R/12.

I also recently seen in instructions for Wiegmann "NEMA 4/12" enclosures that state to drill weep holes in the bottom of enclosure for NEMA 3R applications. Would need to find such instructions to recall exactly how it was worded, but does indicate to me that if you drill the holes you now have a 3R enclosure - though it is still much more water tight then many other 3R enclosures.

 

[Jraef]

Instructions for a NEMA 12 panelboard cabinet I have installed frequently say to remove the drain screws in the bottom of the cabinet for NEMA 3R applications. I would assume if the screws are removed it is now a 3R cabinet. It is identified in the catalog as NEMA 3R/12.

I also recently seen in instructions for Wiegmann "NEMA 4/12" enclosures that state to drill weep holes in the bottom of enclosure for NEMA 3R applications. Would need to find such instructions to recall exactly how it was worded, but does indicate to me that if you drill the holes you now have a 3R enclosure - though it is still much more water tight then many other 3R enclosures.

Carefully worded. What they say is that if you want to use it in a 3R application, you modify it. But they DON'T say the box BECOMES type 3R. UL has dealt with this issue repeatedly and forced enclosure manufacturers, like Hammond in particular, to cease stating that the ENCLOSURE was listed as 12/3R if it was not specifically LISTED as a 3R. But that then can't really be done because the two specs have conflicting requirements, so it requires FIELD modification, which UL cannot be ensured happened correctly.

You can have 12/4 listings, because thwe difference is only in the clamping and gasketing materials, so if you have Type 4, it's easier to list it as type 12. Type 4 is listed for outdoor use, so that's fine, but 3R LISTING requires a weep hole for condensation, which violates type 4.

Yes, it's semantics, but I have been burned by the semantics with AHJs bent on rigid interpretations. Reasonable people tend to make reasonable judgements, but understand that it is still a judgement which means you might get burned if you claim something that does not actually get backed up by facts.