I am working in a Div I class II hazardous location. Based off the nfpa 497 (recommended practice for the classification of flammable liquids, gases, or vapors, and of hazardous locations for electrical installations in chemical process area) and from what i have interpreted in that publication, can i declassify an area in a room based off figure 5.9.1(e) that is located above an area used to store acetone (this being the most flammable chemical being stored). The area i want to declassify is the ceiling. I would like to run emt and use standard installation techniques for my lighting that are normally used in a declassified area. The lights i am installing are rated for this location. It seems to me that this is ok as long as my electrical installations are at least 8ft above the materials being stored. Also the area i am working in is ventilated. If this seems to be within code my next question is do the lights need seal offs?
Declassifing a hazardous location
- Thread starter mikex109
- Start date
- Status
Acetone is a liquid which is Class I. (Did you mean a Class I Division II room or a Class I Division I room)
If the area is Class I Division I , diagram 5.9.1e can not be utilized as you described.
However,
If the area is Class I Division II, you may be able to utilize diagram 5.9.1e
Is their adequate ventilation in the room?
Per NFPA 497
3.3.1 Adequate Ventilation
A ventilation rate that affords either 6 air changes per hour, or 1 CFM per squate foot of floor area, or other similar criteria that prevent the accumulation of significant quantoties of capor-air concentration from exceeding 25 percent of the lower flammable limit.
If the ventilation can be classified as adequate per NFPA 497 you could possibly declassify the ceiling area.
If there isn't adequate ventilation you must leave the room as Class I Division II and installation must utilize rated fixtures and approved wiring methods.
Typicaly a Class 1 Division II fixture will not require a conduit seal at the fixture. Conduits entering the classified areas will need to be sealed per NEC
If the area is Class I Division I , diagram 5.9.1e can not be utilized as you described.
However,
If the area is Class I Division II, you may be able to utilize diagram 5.9.1e
Is their adequate ventilation in the room?
Per NFPA 497
3.3.1 Adequate Ventilation
A ventilation rate that affords either 6 air changes per hour, or 1 CFM per squate foot of floor area, or other similar criteria that prevent the accumulation of significant quantoties of capor-air concentration from exceeding 25 percent of the lower flammable limit.
If the ventilation can be classified as adequate per NFPA 497 you could possibly declassify the ceiling area.
If there isn't adequate ventilation you must leave the room as Class I Division II and installation must utilize rated fixtures and approved wiring methods.
Typicaly a Class 1 Division II fixture will not require a conduit seal at the fixture. Conduits entering the classified areas will need to be sealed per NEC
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
mikex109 said:
I think the answer is that potentially it could be de-classified.
However, I do not believe you are the person who can do it.
not my decision
not my decision
bob i understand its not my decision, ultimately it is up to the owner of the manufacturing plant and their insurance company. The situation i am in is one of a complicated nature and it would take a while to explain. This is something i am just geeking out on to learn more about hazardous classifications and i do appreciate all the input from whoever responds to my post. I am a firm believer in researching and learning all i can about whatever projects i am working on so thanks to all for replying.
not my decision
bob i understand its not my decision, ultimately it is up to the owner of the manufacturing plant and their insurance company. The situation i am in is one of a complicated nature and it would take a while to explain. This is something i am just geeking out on to learn more about hazardous classifications and i do appreciate all the input from whoever responds to my post. I am a firm believer in researching and learning all i can about whatever projects i am working on so thanks to all for replying.
explosion proof boxes
explosion proof boxes
lets say for instance that the whole room including the ceiling remains classified as a class I div II location. Under the boxes and fittings section of wiring methods used for class I div II locations in the 2005 nec. (it is marked as having been updated from the 2002) ive interpreted that the boxes I use don't have to be explosion proof unless they contain some sort of device, meter, relay, equipment, ect. I cant say what the exact article num i read this under its to early and ive got to get ready for work but i read it yesterday. so if i am correct then i can use just a regular malleable rigid box as a junction box for wire splices in the ceiling with no seals around that specific box just seals on the pipe entering in the room 10 ft from the wall on either side and seals within 18 in from all pipes entering and exiting fixtures and their switches, (with the switches and their enclosures being rated for class I div II). For that matter could i just use a regular 4 square (not that i would). FYI, the only power in this room is the lighting power im asking about. Thanks guys!!!
explosion proof boxes
lets say for instance that the whole room including the ceiling remains classified as a class I div II location. Under the boxes and fittings section of wiring methods used for class I div II locations in the 2005 nec. (it is marked as having been updated from the 2002) ive interpreted that the boxes I use don't have to be explosion proof unless they contain some sort of device, meter, relay, equipment, ect. I cant say what the exact article num i read this under its to early and ive got to get ready for work but i read it yesterday. so if i am correct then i can use just a regular malleable rigid box as a junction box for wire splices in the ceiling with no seals around that specific box just seals on the pipe entering in the room 10 ft from the wall on either side and seals within 18 in from all pipes entering and exiting fixtures and their switches, (with the switches and their enclosures being rated for class I div II). For that matter could i just use a regular 4 square (not that i would). FYI, the only power in this room is the lighting power im asking about. Thanks guys!!!
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
In general, this sounds like a pretty good understanding; but I would like to clarify something.
Section 501.10 (B)(4) does indeed state ?? Boxes and fittings shall not be required to be explosionproof except as required by 501.105(B)(1), 501.115(B)(1), and 501.150(B)(1).? However, this does NOT mean ?For that matter could i just use a regular 4 square (not that i would).? Section 501.30 and 250.100 would still prohibit a ?regular 4 square? for the application described in the OP.
Section 501.10 (B)(4) does indeed state ?? Boxes and fittings shall not be required to be explosionproof except as required by 501.105(B)(1), 501.115(B)(1), and 501.150(B)(1).? However, this does NOT mean ?For that matter could i just use a regular 4 square (not that i would).? Section 501.30 and 250.100 would still prohibit a ?regular 4 square? for the application described in the OP.
weressl
Esteemed Member
mikex109 said:
Let's try this again.
CLass I, Division 2.
- Location
- Illinois
- Occupation
- retired electrician
Bob,
[quote Section 501.30 and 250.100 would still prohibit a “regular 4 square” for the application described in the OP.[/quote]
I don't see anything in those sections that would prohbit the use of that type of box. What am I missing?
[quote Section 501.30 and 250.100 would still prohibit a “regular 4 square” for the application described in the OP.[/quote]
I don't see anything in those sections that would prohbit the use of that type of box. What am I missing?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I am thinking a typical 4 square box is part of a wiring system that is not permitted in a C1D2 area.don_resqcapt19 said:
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Thanks for keeping me honest Don; this may be a vernacular issue and I overstated the case. I simply wanted to emphasize that boxes that typically use a double-locknut or locknut/bushing for bonding are still not suitable in Division 2 as they are commonly installed.
- Location
- Illinois
- Occupation
- retired electrician
Bob,rbalex said:
I don't see why you can use the box, you just have to use grounding bushings and jumpers along with it....assuming that the box is otherwise suitable for the environment.
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
I agree - that's why I said I overstated the case. However, most folks won't automatically use "grounding bushings and jumpers" with standard boxes and the post I was responding to gave me the impression that they might not.
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
"Vapor-tight" is not a relevant issue in this case. Even a fully threaded raceway system isn't vapor-tight.
weressl
Esteemed Member
rbalex said:
To further explain.
If teh segment of the conduit needs to be explosionproof then all fittings should be XP rated. Class I, Div. 2 wiring allows the use of wiring methods taht do not require the use of an XP conduit system. Any other wiring methods used may utilize fittings that are offering the same level of protection as the wiring method itself and is designed to be used with the wiring method itself.
Intrinsically safe or nonincendive wiring may utilize wiring methods that use '4" boxes'.
- Status