Hazardous Location Class 1 Div 2 On A Building

[chotabaccha]

Hi All,
We have a small chemical storage building (all liquids) that we are going to be installing in the near future. I am part of the electrical team assisting in classification (not done one before). As I am trying to get myself familiar with the NEC standards, I was hoping I could get some insight. The building should have adequate ventilation so the building will be classified as Class 1 Div 2.
The building will come pre-wired from the manufacturer of the building. It will have an explosion proof heater installed in it. I will find out the Temp code of the chemicals and based on that get the heater ordered. Lights installed will be explosion proof as well. All the circuits come to the breaker panel. At first, the breaker panel was going to be inside the building, but now we are deciding for it to be put outside. It will then be a weatherproof breaker panel (because outside location). My question was should the breaker box be rated class 1 div 2 even though it is not inside the building? The raceway out of the breaker panel and going into the building for heater and lights should be sealed, correct?
I am trying to learn the codes and standards as I go along, any help will be greatly appreciated. Thanks.

 

[rbalex]

I usually recommend beginning with NFPA 497 to determine what your area classification should be. Unless it is subject to Articles 511 to 516 it is virtually impossible to classify from Article 500 alone.

The luminaries (light fixtures) are not likely to be required to be explosionproof. See Section 501.130(B)

The panel may need to be explosionproof depending on where it is located with respect to other openings in the building. There is likely to be a small Division 2 envelope around those openings outside the building. See Section 501.10(B).

Whether inside or out, if the panel is required to be explosionproof you will definitely need to seal it. Depending on your Division 2/unclassified boundary you may (only may) be able to have a single seal do double duty. Read Section 501.15(B) very carefully.