NFPA 30 Electrical area classifications

[reluminate]

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?

 

[rbalex]

Because it is Class IB material, the primary storage room itself is pretty well locked in as entirely Division2. You will probably be comforted that the tertiary rooms can be ignored – or the whole building would ultimately be classified.

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.

 

[stookeyfpe]

This is interesting. It's always been my understanding from NFPA 30, Table 7.3.3 that a room used strictly for the warehousing of Class I flammable liquids is classified as Ordinary electrical service, but when storage occurs, it becomes a Division 2 location.

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.

 

[rbalex]

It is a very specific appliccation; in the case of interior rooms (entirely surrounded by other rooms)Table 7.3.3 (4th line from the bottom) dictates that it be Division 2. You are probably thinking about the third line from the bottom. I assumed the OP knew the conditions. NEC Table 515.3 says essentially the same thing. (Art 515 is largly extracted from NFPA 30)

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.

 

[reluminate]

rbalex – are you saying that the 4th line from the bottom (Inside rooms or storage lockers used for the storage of Class 1 liquids) only applies if the room is entirely surrounded by other rooms? The room that I am evaluating has other rooms on three sides and one outside wall (with openings). Does that mean that this room would comply with the 3rd line from the bottom (Indoor warehousing where there is no flammable liquid transfer) and have ordinary classification?

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.”.

 

[rbalex]

You moved the goal posts. Most of the time, I tell folks I can't give detailed advice without knowing the details of the installation - I should have this time too.

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.

 

[reluminate]

OK. I reviewed these sections again and looked to see if others might apply. Chapters 12 and 17 refer back to Chapter 7 and Chapter 9 pretty much states the same as Table 7.3.3 regarding electrical classification. They all indicate that ventilation is required, but nothing I could find tells me that ventilation allows you to change electrical 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?

 

[rbalex]

That's why I said it's a generality. That said, "totally enclosed within the building" means it is an interior room totaly surrounded by other rooms. A single outside wall removes the requirement that it be Division 2 - even if the wall has no direct access to the outside. Why this is so I've never found out. It is a VERY old requirement from NFPA 30's perspective. It is probably old enough that current Technical Committee members couldn't tell you why.

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.

 

[rbalex]

Correction: That should have been NFPA 497, Section 5.5.4.

 

[reluminate]

rbalex, thanks for your patience and taking the time to answer my posts.

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.

 

[rbalex]

One possible approach is to ask what other reasonable interpretation could be derived from comparing the texts of the Table 7.3.3 third and fourth from bottom lines.

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.