NEMA 7 and XP enclosure

timchengyong

Member
Location
China
Type 7 enclosures are intended for use indoors, in the atmospheres and locations defined as Class 1, Division1 and Group A, B,C,D in NEC. So what's the difference between NEMA7 and XP enclosure? Why normally Ex box has both marks in the nameplate? Thanks!
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
We indicated in one of your earlier inquiries, that your location in China may be affected by any number of Codes and Standards. This may also be affected by the location of the end-products installation.

A nameplate's markings may indicate an enclosures identification under multiple Standards, both US domestic or international.

For all practical purposes, a Type 7 enclosure is synonymous with explosionproof in US domestic applications. Some manufactures may use both marks. If "Type 7" and/or "explosion-proof" were the only markings, then the enclosure would only be suitable for indoor applications. However, additional "Type" markings, such as "3" or "4" may indicate the enclosure is also suitable for outdoor use.

"Ex" marks indicate an IEC or affiliated Standard has been used to evaluate the enclosure. (A US domestic enclosure for Article 505 use would be marked "AEx") Where they apply under certain ATEX rules, some manufactures may also apply descriptive use statements on their nameplates.
 

myspark

Senior Member
Location
SCV Ca, USA
Occupation
Retired EE
Hello Timchen

The “X” designation in NEMA 7 Enclosures (or other NEMA Types) pertain to EXPLOSION PROOF.
Not all NEMA 7 designated Types are suitable for installations in explosive environment.

Peruse this following publication to get some ideas.
Also USA Standard differs from EU Standard in terms of Explosion Proof equipment suitability. The previous post pretty much explains it.

Logic dictates that whatever is good for higher protection is good for lower “minor protection”. The discretion on where to use each type depends on the discretion of the designing engineer.

Welcome to the Forum.

 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Hello Timchen

The “X” designation in NEMA 7 Enclosures (or other NEMA Types) pertain to EXPLOSION PROOF.
Not all NEMA 7 designated Types are suitable for installations in explosive environment.

Peruse this following publication to get some ideas.
Also USA Standard differs from EU Standard in terms of Explosion Proof equipment suitability. The previous post pretty much explains it.

Logic dictates that whatever is good for higher protection is good for lower “minor protection”. The discretion on where to use each type depends on the discretion of the designing engineer.

Welcome to the Forum.

An "X" appended to a Type indicates corrosion protection as indicated in NEC Table 110.28 (You do have to read it carefully)

I don't usually rely too heavily on manufacture's literature, but the PDF you supplied indicates Type 7 means, " For use in indoor locations defined as Class I, Groups A, B, C, or D as defined in the National Electrical Code." Where would it suggest, " Not all NEMA 7 designated Types are suitable for installations in explosive [sic] environment." [Actually, they aren't suitable for Class II, but explosionproof isn't suitable for Class II anyway. (Section 502.5)]
 

myspark

Senior Member
Location
SCV Ca, USA
Occupation
Retired EE
My experience in MIL Specs usually incorporporate mandates outside NEC. I spent a year as specs writer with the office of the OICC (Officer in Charge of Construction Contracts).

In some of the provisions--they are based on precedents . . .meaning some of the articles are cut and paste.
I observed my wife also do the same thing on some drawings where she instructs the draftsperson to do the same thing. There were no CAD at the time.
She is a degreed and Certified Architect but now retired. This doesn't mean her smarts telegraphs in my direction. . .but I do pick up something a little bit being in a different discipline.
Thanks for the grammar correction.
 

timchengyong

Member
Location
China
We indicated in one of your earlier inquiries, that your location in China may be affected by any number of Codes and Standards. This may also be affected by the location of the end-products installation.

A nameplate's markings may indicate an enclosures identification under multiple Standards, both US domestic or international.

For all practical purposes, a Type 7 enclosure is synonymous with explosionproof in US domestic applications. Some manufactures may use both marks. If "Type 7" and/or "explosion-proof" were the only markings, then the enclosure would only be suitable for indoor applications. However, additional "Type" markings, such as "3" or "4" may indicate the enclosure is also suitable for outdoor use.

"Ex" marks indicate an IEC or affiliated Standard has been used to evaluate the enclosure. (A US domestic enclosure for Article 505 use would be marked "AEx") Where they apply under certain ATEX rules, some manufactures may also apply descriptive use statements on their nameplates.
Thanks for your clear explanation! My another inquire is if end user can drill holes or change inside electrical components of an explosionproof enclosure without re-certificate?
 

timchengyong

Member
Location
China
Hello Timchen

The “X” designation in NEMA 7 Enclosures (or other NEMA Types) pertain to EXPLOSION PROOF.
Not all NEMA 7 designated Types are suitable for installations in explosive environment.

Peruse this following publication to get some ideas.
Also USA Standard differs from EU Standard in terms of Explosion Proof equipment suitability. The previous post pretty much explains it.

Logic dictates that whatever is good for higher protection is good for lower “minor protection”. The discretion on where to use each type depends on the discretion of the designing engineer.

Welcome to the Forum.

Thanks for your sharing!
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Thanks for your clear explanation! My another inquire is if end user can drill holes or change inside electrical components of an explosionproof enclosure without re-certificate?
This answer is with respect to US domestic practices. The best assumption, without knowing all of the details of the enclosure and its contents is no.
 

timchengyong

Member
Location
China
This answer is with respect to US domestic practices. The best assumption, without knowing all of the details of the enclosure and its contents is no.
Thanks. I saw one Adalet EXPLOSIONPROOF ENCLOSURES "Conduit Drilling and Tapping Guidelines", it didn't mention inside components, so I want to know more details.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
First - Is the enclosure you that you want to modify an Adelet enclosure? Otherwise, don't rely on the document as a general answer; it can only be correctly applied to Adelet enclosures. Contact the original manufacturer about the specific enclosure you want to modify. Some enclosures may be field modified, while others, even from the same manufacture, cannot.

Second, some assemblies (enclosure and contents) are listed or labeled as a whole and cannot be modified without being recertified. Some contents are listed or labeled separately from the enclosure and still cannot be modified without being recertified. Again you must contact the original manufacturer.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
It's Adalet, a scott Fettzer company. Yes, cousulting original manufacture is a good choice for end user. If there is a code statement of responsibilities of end user and manufacture about Ex equipments?
Section 110.3(B) is a general statement about using any listed or labeled (certified) product including the use of hazardous location equipment.

NOTE: There is a broad range of material that may be considered "... instructions included in the listing or labeling." This could include information in the product test standards, manufacturer's installation instructions. etc.
 
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