Stainless Steel Purged Enclosure

[Richard S]

We need to provide a 120v circuit to a chemical dispense unit that is a type Z purged/pressurized enclosure (I believe it's type Z, but am waiting for official response from vendor/installer). The enclosure is stainless steel and just has knockouts for power and communications termination and not threaded hubs. The room the dispense unit is located is rated C1D2. Being that this is a C1D2 environment and the enclosure is Z purged, per 501.15(B)(2)Exc.3: "Conduit systems passing from an enclosure or room that is unclassified as a result of pressurization into a Class I, Division 2 location shall not require a seal at the boundary.", do we not need to provide a seal within 18" of the enclosure? If not, would that change if it were a X or Y type pressurizing?

Since there is not a threaded hub on the pressurized enclosure, is there a specific fitting needed? Would we just installing a sealing locknut or hub suffice and is this covered in the NEC?

Thanks for the input

 

[bobgorno]

Technically you would not need a seal at the enclosure, however youy will still need one at the boundary of your room when you transition to non-hazardous.

You will have to seal the conduits to prevent air leakage. The best way to do that is to seal the conduits entires from the inside of the enclosure. Dux seal is a good way to prevent air leakage.

For bonding requirements of the conduit entries you can not rely on locknuts. Using a Myers hub will keep the Type 4 integrity of the enclosure and is an apporved bonding device.

Bonding requirements intended to address electrical equipment installed in a Class 1, Division 1 or Division 2 locations are covered by NEC Article 501.30, 250.100 & 250.92(B).