NFPA 30 Electrical area classifications
NFPA 30 Electrical area classifications
(OP)
I'm working on determining the electrical classification in a building that has a storage room where they store Class 1B flammable liquids. As I read Table 7.3.3, that entire room would be classified as NEC Class 1, div 2, zone 2.
There are other indoor rooms in the building adjacent to this storage room that have doors opening into it. These rooms are used for warehousing non-flammable liquids, offices, labs and electrical room.
If I'm interpreting Table 7.3.3 correctly, if an ordinary classified room opens into a room that is entirely classified, then that room is also entirely classified. Is this a correct interpretation? If so, what about rooms that open into rooms that open into rooms that are classified?
There are other indoor rooms in the building adjacent to this storage room that have doors opening into it. These rooms are used for warehousing non-flammable liquids, offices, labs and electrical room.
If I'm interpreting Table 7.3.3 correctly, if an ordinary classified room opens into a room that is entirely classified, then that room is also entirely classified. Is this a correct interpretation? If so, what about rooms that open into rooms that open into rooms that are classified?





RE: NFPA 30 Electrical area classifications
But the secondary rooms are a problem. Basically it depends on what activities are carried out in the storage room and the ventilation of the secondary rooms.
RE: NFPA 30 Electrical area classifications
I see no difference in either warehousing or storage. My contention has always been that when the liquid is placed into a open system use, that's when HAZLOC becomes applicable. In other words, simply storing or warehousing a Class IB liquid is Ordinary electrical service.
RE: NFPA 30 Electrical area classifications
I agree that ventilation, container size, room size, non-transfer of flammables, etc., should affect this, but it doesn't for reasons only the Tech Committee for NFPA 30 can say for sure. If NFPA 497 were the basis, it would be slightly different.
RE: NFPA 30 Electrical area classifications
The room is ventilated. The Class 1 liquids are stored in palletized 55 to 250 gallon drums. There are overhead doors that are normally open into some of the secondary rooms. There is almost constant fork truck traffic in and out of the room during working hours.
I'm struggling to understand if there is a difference between warehousing and storage, as well as the applied logic in this application. I did see that Note 1 to the table states "The release of class 1 liquids may generate vapors to the extent that the entire building, and possibly an area surrounding it, should be considered a class 1, division 2, zone 2 location", however, that only would apply if there is a flammable vapor-air mixture under normal operation or as stookeyfpe referred to as "liquid placed into a open system use.".
RE: NFPA 30 Electrical area classifications
You need to review the "Scope" (x.1), "Electrical" (x.12) and "Ventilation" (x.14) Sections of Chapters 9 and 12 and possibly other Chapters that may apply. (Only you know which ones do)
Generally, in an adequately ventilated room (typically 1cfm/ft2 of floor space) rooms that only store but do not otherwise transfer materials can usually be "unclassified." This is only a generality, but applies the great majority of times.
RE: NFPA 30 Electrical area classifications
I guess the thing my brain cell hasn't been able to pick up is the definition of "totally enclosed within the building" as used in 9.12.2 and "Inside rooms" as used in Table 7.3.3. Does one outside wall mean that this is not a totally enclosed room or inside room?
RE: NFPA 30 Electrical area classifications
Most electrical area classification recommended practices, e.g, NFPA 497 or API RP 500 are based on the experiences of their technical committees rather than hard analysis - unless you want to do a fugitive emmissions study. See NFPA 497, Section 5.4.4 for example. (There are plenty of references to "experience" throughout the document) When the NFPA 30, Table 7.3.3 requirement was first established, it was probably based on the experience of some member.
RE: NFPA 30 Electrical area classifications
RE: NFPA 30 Electrical area classifications
I like your definition of an interior room and would like to find something in the codes or standards that clearly support that definition. I've been through every NFPA code that I think applies to this application and also looked through the IBC without finding anything.
The closest definition I can find that seems to fit the space I'm reviewing is in NFPA 30 3.3.1.3 – Inside Liquid Storage Area. That takes me back to believing that the 4th line up in Table 7.3.3 applies and the area would be classified Class 1, div 2.
I'd really like someone to prove that my interpretation is wrong and direct me toward code references that I can use to present to the local AHJ. He can be reasoned with if there is something in black & white, however getting him to buy into the "Experience has shown..." or "That's the way it has always been done" theories would be pushing it.
RE: NFPA 30 Electrical area classifications
If you can't get your AHJ representative to buy into the "experience" argument based on an ANSI sanctioned document's own text; e.g., NFPA 497, Section 5.5.4 you definitely have a problem because you won't find it anywhere else.