What? General purpose equipment in Class 1 Div2? [examples]........Just to name a couple
I apologize for potentially creating some confusion. I just want to clarify my position. (This time you get the long version... yet still incomplete version.)
As I said in my post I was giving the short answer, but, it seems that the short answer may have given an incomplete understanding of the code requirements.
Luckyshadow specifically you were asking about a room with an oxygen cascade and your concern that it may be a Class I Division 2 area. You did not give us any information concerning the occupancy of the building or the presence of other hazards, so, we are left with applying very generalized requirements.
Actually this is three questions in one:
1. Does the presence of oxygen create a classified area?
2. If it does create a classified area, what Classification category is applied to the area?
3. If this is a Class I Division 2 area, is general purpose equipment appropriate for installation? Your examples of concern include receptacles, light switches, and surface mounted lights.
Before I answer the question it is important to explain a basic ground rule for the use of the NEC in classified areas. The NEC is not
a classification document. You apply the NEC after consulting other documents that classify areas. Once you determine the type of area based on the appropriate standard or recommended practice, the NEC is used to determine the installation method and equipment that is appropriate for the area.
In order to apply another document (standard or practice) and actually determine the classification, you need to know the occupancy of the structure and what NFPA documents may apply. Or, you follow the general guidelines in the FPN that is at the beginning of Article 500.
FPN:Rules that are followed by a reference in brackets contain text that has been extracted from NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 1997 edition, and NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installation in Chemical Process Areas, 1997 edition. Only editorial changes were made to the extracted text to make it consistent with this Code.
A few other documents that need to be consulted include:
NFPA 30, Flammable and Combustible Liquids Code
NFPA 30A, Code for Motor Fuel Dispensing Facilities and Repair Garages
NFPA 32, Standard for Drycleaning Plants
NFPA 33, Standard for Spray Application Using Flammable or Combustible Materials
NFPA 34, Standard for Dipping and Coating Processes Using Flammable or Combustible Liquids
NFPA 35, Standard for the Manufacture of Organic Coatings
NFPA 36, Standard for Solvent Extraction Plants
NFPA 45, Standard on Fire Protection for Laboratories Using Chemicals
NFPA 50A, Standard for Gaseous Hydrogen Systems at Consumer Sites
NFPA 50B, Standard for Liquefied Hydrogen Systems at Consumer Sites
NFPA 51, Standard for the Design and Installation of Oxygen-Fuel Gas Systems for Welding, Cutting, and Allied Processes
NFPA 51A, Standard for Acetylene Cylinder Charging Plants
NFPA 52, Compressed Natural Gas (CNG) Vehicular Fuel Systems Code
NFPA 54, Natural Fuel Gas Code
NFPA 58, Liquefied Petroleum Gas Code
NFPA 59, Utility LP-Gas Plant Code
NFPA 59A, Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG)
NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Products Facilities
NFPA 85, Boiler and Combustion Systems Hazards Code
NFPA 88A, Standard for Parking Structures
NFPA 88B, Standard for Repair Garages
NFPA 99, Standard for Health Care Facilities
NFPA 407, Standard for Aircraft Fuel Servicing
NFPA 409, Standard on Aircraft Hangars
NFPA 480, Standard for the Storage, Handling, and Processing of Magnesium Solids and Powders
NFPA 481, Standard for the Production, Processing, Handling, and Storage of Titanium
NFPA 495, Explosive Materials Code
NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment
NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
NFPA 651, Standard for the Machining and Finishing of Aluminum and the Production and Handling of Aluminum Powders
NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
NFPA 655, Standard for Prevention of Sulfur Fires and Explosions
NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities
Based on the limited information given, here are some additional points concerning my post. Again, this is a summary, we don't have time or space for a complete discussion on the classification of spaces, that's part of a five day course offered by NFPA.Question #1
Does the presence of oxygen create a classified area?Answer
No. Oxygen is a non-flammable gas. While it may increase the chances for an explosion or fire in the presence of a flammmable or combustible vapor/gas/dust mixture, the presence of oxygen in an area does not itself require explosion proof electrical wiring methods. (Article 500.6) bold added
500.6 Material Groups.
For purposes of testing, approval, and area classification, various air mixtures (not oxygen-enriched) shall be grouped in accordance with 500.6(A) and 500.6(B).
The NEC Handbook offers guidance on the hazards of oxygen.
Oxygen enrichment can drastically change the explosion characteristics of materials. It lowers the minimum ignition energies, increases explosion pressures, and can reduce the maximum experimental safe gap, rendering both intrinsically safe and explosionproof equipment unsafe unless the equipment has been tested for the conditions involved.
So... unless there are other materials present or expected in the future at this project. The area with oxygen is not classified.Question #2
If it does create a classified area, what Classification category is applied to the area?Answer
This point is moot based on my answer to question one.Question #3
If this is a Class I Division 2 area, is general purpose equipment appropriate for installation? For example, receptacles, light switches, and surface mounted lights.Answer
The basic question of classification has been answered for this circustance. But, let's go out on a limb here and assume that there is something else (other than oxygen) that would cause this are to be classified as Class I Division 2, can you use "general purpose" equipment in this type of area?
Yes (sometimes). I should have prefaced (but in the interest of brevity originally I left it out) that Class I Division 1 always requires explosion proof equipment... and/or adequate ventilation. Class I Division 2 may require explosion proof equipment, but, often you can use general purpose equipment. Particularly for boxes and fittings. For example, Article 500.8(A)(3) allows the use of general purpose equipment.
500.8(A)(3) Where specifically permitted in Articles 501 through 503, general-purpose equipment or equipment in general-purpose enclosures shall be permitted to be installed in Division 2 locations if the equipment does not constitute a source of ignition under normal operating conditions.
The NEC Handbook explanation of one of these circumstances:
In Class I, Division 2 locations, boxes, fittings, and joints are not required to be explosionproof at lighting outlets or at enclosures containing no arcing devices, such as solenoids and control transformers, if the maximum operating temperature of any exposed surface does not exceed 80 percent of the ignition temperature in degrees Celsius.
A similar allowance to the above also exists for luminaries in 70-2005, 500.130(B)(1)
Where lamps are of a size or type that may, under normal operating conditions, reach surface temperatures exceeding 80 percent of the ignition temperature in degrees Celsius of the gas or vapor involved, fixtures shall comply with 501.9(A)(1) or shall be of a type that has been tested in order to determine the marked operating temperature or temperature class (T Code).
Which means... if you don't exceed 80% of the temperature of the gas/vapor in the area ((and we do not apparently have a flammable gas or vapor) then you can use general purpose lighting.
The 2002 NEC Handbook (soory don't have the new handbook yet) also provides the following explanation of the hazards involved with fuses and/or circuit breakers in a Class I Division 2 location:
In Class I, Division 2 locations, it is assumed that fuses or circuit breakers will seldom open the circuit where used to protect feeders or branch circuits supplying lamps in fixed positions only. Division 2 locations are not normally hazardous but may become so [see 500.5(B)(2)(3)], and because it is unlikely that the fuse or circuit breaker in such a circuit will operate simultaneously with the occurrence of an explosive mixture inside the enclosure, general-purpose enclosures are permitted for such overcurrent devices.
Obviously, while on its face this post may seem to pose simple questions there are in fact no simple answers... especially without more information.
BTW, nobody (with the exception of Yoop) seemed to fully give their opinion on any of the other issues that were not related to the classification of the space. Let's step up and give the guy an opinion on let's say the use of the greenfield (FMC). I don't see anything that prohibits it, but, what do you guys think?
I'm not an engineer, but, let's not bash the comments of the engineer without more background. Maybe he's right... then again maybe he's wrong. We really don't know.
I do agree that you should always question something if it doesn't seem right... and make the person that is giving you the information back it up with documentation. If they can't or won't, then ignore them and move on...
Lucky... you seem conscientious and that's always commendable.
[This message has been edited by safetygem (edited 01-28-2005).]