Help determining if an area is a Class I div II location or not.

[Nick Palermo]

We have a sewage pump dry well vault that has pumps and piping passing through. The vault has a control panel and two motors. The question is if there is 24hr ventilation of the vault is the area still considered classified? Also, if the ventilation is shut off and only used during entry what would that due to the rating?

 

[rbalex]

You will want to consult both NFPA 496 and 820. NFPA 820 will help determine what the “basic” area classification should be. Ventilation does count, but NFPA 496 puts some fairly strong restrictions on the system if ventilationfails.

Edit Add: See also NEC Section 500.5(B)(2)(2) and (3).

 

[kenaslan]

You will want to consult both NFPA 496 and 820. NFPA 820 will help determine what the ?basic? area classification should be. Ventilation does count, but NFPA 496 puts some fairly strong restrictions on the system if ventilationfails.

Edit Add: See also NEC Section 500.5(B)(2)(2) and (3).

I believe that you want to consult NFPA 497 Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installions in Process Areas

NFPA 496 is Standard for Purged and Pressurized Enclosures for Electrical Systems

But the Holy Grail will always be NFPA 70 the NEC

Ken

 

[rbalex]

NFPA 820 is specific for Fire Protection in Wastewater Treatment and Collection Facilities. It refers to both NFPA 496 and 497. Chapters 4, 5 & 6 have extensive Tables describing proper electrical area classification. Chapter 9 is for the applications of ventialtion

Only if the Tables in Standard 820 don't apply should anyone attempt to use NFPA 497 for wastewater applications. The NFPA 820 Technical Committee has already made most of the judment calls in the Tables.

If the OP wants to use ventilation as a basis, NFPA 496 is appropriate for evaluating ventilation systems by other than "natural" means.

Except for Articles 510-516, anyone who attempts to classify a location directly from the NEC, doesn't understand what they are doing. See Section 500.4(B) and especially FPN No.1. FPN No.2 also specifically references NFPA 820.