Class 1, Division 1 boundary 501.15 (A) (4) Exception 1

[Al Rolston]

If I have two small Ex enclosures (Located in a C1, D1 area) rated C1, D1, and connect between them with a straight piece of conduit (less than 12 inches long and less than 2" size), I don't need a seal fitting because the interior of each of the Ex enclosures is "Un Classified". Yes, all the other openings in each enclosure is protected with seal fittings. Is this a correct interpretation?

 

[nhee2]

If the boxes are explosion-proof, and at least one of them contains arcing/sparking devices (ref 501.15(A)(1)), then a seal is required in the 12" conduit run. A single seal is sufficient since it will be within 18" of each box (ref 501.15(A)(3)).

If neither box contains arcing/sparking devices then no seal is required.

 

[rbalex]

I concur with nhee2.

I would note that 501.15(A)(4) Exception 1 does not apply since you are describing enclosure seals rather than boundary seals and the enclosures interior's are nevertheless Class I, Division 1.

I'm also curious how you managed to get a short piece of conduit between the enclosures without a union.

 

[Al Rolston]

Ex sealed enclosures interiors are definitely un classified .

Ex sealed enclosures interiors are definitely un classified .

Ex sealed enclosures interiors are definitely un classified. The enclosures are loose and just screw one onto the conduit.

I concur with nhee2.

I would note that 501.15(A)(4) Exception 1 does not apply since you are describing enclosure seals rather than boundary seals and the enclosures interior's are nevertheless Class I, Division 1.

I'm also curious how you managed to get a short piece of conduit between the enclosures without a union.

 

[rbalex]

Ex sealed enclosures interiors are definitely un classified...

What is your basis for that? Neither the seals nor explosionproof enclosures are gas/leak-proof. In fact, explosionproof enclosures are designed to "breath" and seals are permitted to leak.

... The enclosures are loose and just screw one onto the conduit.

OK, I was just curious, but a "loose" assembly definitely won't keep gases out of the enclosure and usually runs the risk of violating Section 500.8(E)(1) or (2) and possibly 501.30.

 

[nhee2]

Ex sealed enclosures interiors are definitely un classified. The enclosures are loose and just screw one onto the conduit.

I do not understand what you mean when you say the enclosure interiors are unclassified. Are they purged? What makes them unclassified?

 

[Al Rolston]

Un classified inside an Ex enclosure.

Un classified inside an Ex enclosure.

Ex sealed enclosures interiors are definitely un classified. The enclosures are loose and just screw one onto the conduit.

Think about it, spark producing devices are only allowed to exist in an un classified area. Thus the interior of a properly sealed enclosure with spark producing devices is un classified.

 

[rbalex]

"Think about it, spark producing devices are only allowed to exist in an un classified area..." OR in an explosionproof enclosure [Section 501.15(A)(1)(1)] OR by using some other recognized protection technique.[Section 500.7]

You should also carefully review the definition of explosionproof equipment in Section 500.2 so you will have a correct understanding how it works.

Explosionproof Equipment. Equipment enclosed in a case that is capable of withstanding an explosion of a specified gas or vapor that may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited thereby.

Explosions can, and do, occur in explosionproof equipment - commonly in Class I, Division 1; not so often in Class I, Division 2 (but it can still happen).

BTW, unclassified is also a defined in Section 500.2 and there is no space between "un" and "classified".

 

[Al Rolston]

Class 1 Div1, boundary

Class 1 Div1, boundary

"Think about it, spark producing devices are only allowed to exist in an un classified area..." OR in an explosionproof enclosure [Section 501.15(A)(1)(1)] OR by using some other recognized protection technique.[Section 500.7]

You should also carefully review the definition of explosionproof equipment in Section 500.2 so you will have a correct understanding how it works.

Explosions can, and do, occur in explosionproof equipment - commonly in Class I, Division 1; not so often in Class I, Division 2 (but it can still happen).

BTW, unclassified is also a defined in Section 500.2 and there is no space between "un" and "classified".

Thank for pointing out where I was wrong. Appreciate the help.