Conduit and Seals for Explosion Proof Enclosures in Class I Div 2 Area?

[TwoBlocked]

I think I have this figured out, but would like input from you fine folks. All Code references are from the 2023 NEC.

When the NEC mentions an explosionproof enclosure, I picture one of those cast aluminum bolted boxes with breakers or contactors in it. But a measuring device such as pressure transmitter that is listed as explosionproof would also be such an enclosure, right? So when running conduit in a Class I Div 2 area to such a measuring device, the conduit must be sealed as per 501.15 (B) (1) (which further references Class I Div 1 wiring methods). So before the seal, Class I Div 2 wiring methods are allowed such as listed LFMC and condulets with gasketed covers, but between the seal and the explosionproof measuring device Class I Div 1 wiring methods are required such as capped elbows and explosionproof unions, right? Of course a boundary seal will probably be required when transitioning to an unclassified area.

Am I missing anything?

 

[Dsg319]

I think I have this figured out, but would like input from you fine folks. All Code references are from the 2023 NEC.

When the NEC mentions an explosionproof enclosure, I picture one of those cast aluminum bolted boxes with breakers or contactors in it. But a measuring device such as pressure transmitter that is listed as explosionproof would also be such an enclosure, right? So when running conduit in a Class I Div 2 area to such a measuring device, the conduit must be sealed as per 501.15 (B) (1) (which further references Class I Div 1 wiring methods). So before the seal, Class I Div 2 wiring methods are allowed such as listed LFMC and condulets with gasketed covers, but between the seal and the explosionproof measuring device Class I Div 1 wiring methods are required such as capped elbows and explosionproof unions, right? Of course a boundary seal will probably be required when transitioning to an unclassified area.

Am I missing anything?

Some transmitters/valve actuators come hermetically sealed and state on the name plate that seal is not required.

In other cases some will say seal required within such distance.

And if I understand you correctly are you asking if listed fittings for example a LBY or GUA fitting is allowed between the seal and device?

 

[kwired]

Explosion proof enclosures generally is for when the item in question contains arcing/sparking components during normal operation components within such as switching contacts.

Seal is required within 18 inches of the enclosure as it essentially closes off the rest of the raceway from the internal volume of said enclosure to contain pressure of any explosion to the enclosure and limited amount of raceway. If you had a long run of raceway with no seal then effective internal volume that gets pressurized during an explosion could be much more than the enclosure itself. These enclosures are listed/tested to withstand what 18 inches of raceway before a seal conditions would be like.

 

[TwoBlocked]

....

And if I understand you correctly are you asking if listed fittings for example a LBY or GUA fitting is allowed between the seal and device?

More like I am asking if ONLY Class I Div 1 wiring methods (for example a LBY or GUA fitting) is allowed between the seal and the device even though the area is Class I Div 2. Meaning that Class I Div 2 wiring methods, such as LFMC and condulets would NOT be allowed between the seal and the device, even though they are allowed beyond the seal and the device.

 

[Dsg319]

More like I am asking if ONLY Class I Div 1 wiring methods (for example a LBY or GUA fitting) is allowed between the seal and the device even though the area is Class I Div 2. Meaning that Class I Div 2 wiring methods, such as LFMC and condulets would NOT be allowed between the seal and the device, even though they are allowed beyond the seal and the device.

I’m sorry I’m not catching on very fast tonight lol. But you are asking in a Class1 Div2 location with a device that requires a seal are you allowed to have a form7 (gasket fitting) between the seal and the device, as you are allowed with explosion proof fittings in a class1 div1 location.

 

[TwoBlocked]

I’m sorry I’m not catching on very fast tonight lol. But you are asking in a Class1 Div2 location with a device that requires a seal are you allowed to have a form7 (gasket fitting) between the seal and the device, as you are allowed with explosion proof fittings in a class1 div1 location.

I think you are getting to a way that expresses what I am really wondering:


In a classified area, are you ever allowed to use a form 7 between the required seal and a device that is an explosion proof enclosure?

 

[Dsg319]

I think you are getting to a way that expresses what I am really wondering:


In a classified area, are you ever allowed to use a form 7 between the required seal and a device that is an explosion proof enclosure?

That’s a good question. Hopefully someone will chime in and let us know. Because I have never personally done it that I remember.

Typical install for us at a device that needs a seal wether in div1/div2 is union than seal off or union, LBY, than seal off for vertical positions if the port is horizontal.

 

[rbalex]

In a classified area, are you ever allowed to use a form 7 between the required seal and a device that is an explosion proof enclosure?

No. Read Section 501.15(B)(1) and it’s cross references carefully; especially:

Conduit seals shall be installed within 450 mm (18 in.) from the enclosure or as required by the enclosure marking. Only threaded couplings, or explosionproof fittings such as unions, reducers, elbows, and capped elbows that are not larger than the trade size of the conduit, shall be permitted between the sealing fitting and the explosionproof enclosure.

 

[TwoBlocked]

No. Read Section 501.15(B)(1) and it’s cross references carefully; especially:

Right, that's how I read it. Thanks for the confirmation.