NEMA rating for Enclosures

LincHawk

Member
Location
Southeast
What NEMA enclosure rating do I need for a Class 1 Division 1 or 2 areas? I’m just splicing some wire together. No equipment in the enclosures.


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rbalex

Moderator
Staff member
The basic enclosure rules are in Sections 501.10 (A)(3) and 501.10(B)(4).

For splices only, Division 1 enclosures must still be approved for Division 1. Explosionproof is the most common, Other protection technique options may be found in Section 500.7. Be careful to observe Section 501.15(A)(1)(2) as well.

Again for splices only, virtually any enclosure that would otherwise be acceptable in the environment would be suitable.

FYI, the "General Purpose" enclosure "Types" are listed in Section and Table 110.28. While it is still common practice, they are no longer properly called NEMA types.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
But to specifically answer your question, NEMA type 7 is (was) for Class I, Division 1, Groups A, B, C, or D. You can use a NEMA 7 enclosure for Class 1 Division 2 if you like, but often for Division 2 areas you can use regular enclosures with devices inside that are rated for use in Div. 2 environments.

As Bob says though, NEMA types are not official, they are guidelines. OFFICIALLY, the enclosure must be rated, typically by an NRTL such as UL, for the environment it will be used in. UL enclosure types generally match the old NEMA standards (i.e. UL Type 1, 3R, 4, 12 etc.), but UL stops using those designation numbers for classified environments. So for Explosion Proof enclosures, there is no UL Type 7, UL gets specific about Class, Division and Group. But you will see that the explosion proof enclosure mfrs will still market them as NEMA type 7, you just need to ensure what division and group they are listed for.
 

powerpete69

Senior Member
Location
Northeast, Ohio
Occupation
XXX
All true above. Often times when you buy a classified disconnect or enclosure, it will be listed on the spec sheet as Nema 7/9. Which means it will work for Class I or Class II and is applicable for any division 1 or 2. Like they say above, pay close attention to the group listed such as A, B, C or D and make sure it meets your application.

If you are in a Class I area, that means there are explosive gases in the vicinity which means a spark could ignite the gas or even cause an explosion. If you are in a rated area, don't forget that you need threaded rigid conduit with seals. At least 5 threads for your threaded conduit. Keep in mind that sometimes there will be an explosion in your enclosure or disconnect or whatever the case may be. The explosion will cool off as it travels around the 5 threads in front of the seal which keeps the explosion contained and then releases harmlessly in the area. Typically no need to replace the enclosure or disconnect as it is generally a flash on the inside. Look in NFPA 497 for more information, it is all there.

Crouse Hinds also makes a great catalog which details how to properly install conduits in hazardous areas.
 

LincHawk

Member
Location
Southeast
All true above. Often times when you buy a classified disconnect or enclosure, it will be listed on the spec sheet as Nema 7/9. Which means it will work for Class I or Class II and is applicable for any division 1 or 2. Like they say above, pay close attention to the group listed such as A, B, C or D and make sure it meets your application.

If you are in a Class I area, that means there are explosive gases in the vicinity which means a spark could ignite the gas or even cause an explosion. If you are in a rated area, don't forget that you need threaded rigid conduit with seals. At least 5 threads for your threaded conduit. Keep in mind that sometimes there will be an explosion in your enclosure or disconnect or whatever the case may be. The explosion will cool off as it travels around the 5 threads in front of the seal which keeps the explosion contained and then releases harmlessly in the area. Typically no need to replace the enclosure or disconnect as it is generally a flash on the inside. Look in NFPA 497 for more information, it is all there.

Crouse Hinds also makes a great catalog which details how to properly install conduits in hazardous areas.
Could you send me the Crouse Hinds link for this?


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