I'm searching for a code published or industry practice definition for the location term 'pit'. I know the NEC does not offer a definition so the request is for a building code or guidance type document that defines this term. I don't think "... an area often sunken or depressed below the adjacent floor area" provides satisfactory clarity to depth or space (e.g. confined) criteria. I would appreciate any thoughts or opinions forum members have on this matter.
... code language definition
- Thread starter gboynton1
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hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
The NEC mentions the word "pit" in many places, but each is limited to the type and purpose of the pit, mostly found in chapters 5 and 6 and mostly in places of classified areas or elevators, but maybe if you can give us a purpose for the pit I can narrow it down a bit?
Osha has a definition for confined spaces, this definition includes pits. If you are looking for the definition of pit, websters is a good place. If you are looking for the definition of pit to see if it meets the confined spaces criteria, OSHA's definition of confined spaces would cover it.
"Confined space" means a space that:
(1) Is large enough and so configured that an employee can bodily enter and perform assigned work; and
(2) Has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults, and pits are spaces that may have limited means of entry.); and
(3) Is not designed for continuous employee occupancy.
"Confined space" means a space that:
(1) Is large enough and so configured that an employee can bodily enter and perform assigned work; and
(2) Has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults, and pits are spaces that may have limited means of entry.); and
(3) Is not designed for continuous employee occupancy.
iceworm
Curmudgeon still using printed IEEE Color Books
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- North of the 65 parallel
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- EE (Field - as little design as possible)
Not enough information in your post to tell what you are trying to do. If it is a definition for use with the NEC then according to Article 100, Scope, (my interpretation anyway) - In order of preference:
1. Use the definition in the specific article
2. Use the definition in article 100
3. IEEE 100
4. Other applicable, related code
5. Current edition of Funk and Wagnals
The Worm
1. Use the definition in the specific article
2. Use the definition in article 100
3. IEEE 100
4. Other applicable, related code
5. Current edition of Funk and Wagnals
The Worm
application details ???
Area classification is greatly impacted by whether a space qualifies as a 'pit'. The application is multi-fuel industrial engine testing in a cell (i.e. cut-off room) with an inertia mass and bedplate located in the center. Bringing services over to both the engine and dynamometer is usually accomplished via a trench or depressed floor (all but inertia mass area is say 24-inches below the bedplate and covered with open grating).
In addition to testing ventilation, high and low scavenging is provided. When Article 511 (Major Repair Garages is closest NEC match for this occupancy) is applied to this space, the question becomes: how far above the lowest horizontal surface requires rated equipment and wiring methods? The 18 in. classified volume is either entirely in the depressed floor or extends to 42 in. (18 +24).
Sure would be useful for NFPA 70 to carry critical definitions. With regards to hydrogen fuel, NFPA 2 is kind enough to define word such as 'use', as in storage, use, and handling of GH2 and LH2...
Area classification is greatly impacted by whether a space qualifies as a 'pit'. The application is multi-fuel industrial engine testing in a cell (i.e. cut-off room) with an inertia mass and bedplate located in the center. Bringing services over to both the engine and dynamometer is usually accomplished via a trench or depressed floor (all but inertia mass area is say 24-inches below the bedplate and covered with open grating).
In addition to testing ventilation, high and low scavenging is provided. When Article 511 (Major Repair Garages is closest NEC match for this occupancy) is applied to this space, the question becomes: how far above the lowest horizontal surface requires rated equipment and wiring methods? The 18 in. classified volume is either entirely in the depressed floor or extends to 42 in. (18 +24).
Sure would be useful for NFPA 70 to carry critical definitions. With regards to hydrogen fuel, NFPA 2 is kind enough to define word such as 'use', as in storage, use, and handling of GH2 and LH2...
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
NFPA 30: Flammable and Combustible Liquids Code
NFPA 30A: Code for Motor Fuel Dispensing Facilities and Repair Garages
NFPA 37: Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines
NFPA 329: Recommended Practice for Handling Releases of Flammable and Combustible Liquids and Gases
NFPA 423: Standard for Construction and Protection of Aircraft Engine Test Facilities
I suspect you have already reviewed these. NFPA 423 is interesting
Here is an excerpt from NFPA 423:
Interestingly, this is in NFPA 423
So, scrap your Funk and Wagnals.
the Worm
NFPA 30A: Code for Motor Fuel Dispensing Facilities and Repair Garages
NFPA 37: Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines
NFPA 329: Recommended Practice for Handling Releases of Flammable and Combustible Liquids and Gases
NFPA 423: Standard for Construction and Protection of Aircraft Engine Test Facilities
I suspect you have already reviewed these. NFPA 423 is interesting
Here is an excerpt from NFPA 423:
Interestingly, this is in NFPA 423
So, scrap your Funk and Wagnals.
the Worm
- Location
- Mission Viejo, CA
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- Professional Electrical Engineer
I can assure you, you aren't the only person to be frustrated with this problem. Neither the API Subcommittee on Electrical Equipment, (API RP500) nor the NFPA Technical Committee on Electrical Equipment in Chemical Atmospheres (NFPA 497) has developed a definitive technique to address the issue – and they're the “Big Guns” on the subject. In theory, a footprint in the dirt beneath a Division 2 location would be Division 1. Of course you probably won’t have any wiring in it, so that becomes rather immaterial.
Unless you are willing to do a fugitive emissions analysis (API RP500), I can say what you describe will be Class I, Division 1 from the lowest point up to the level where “adequate ventilation” occurs, with an additional 18” Division 2 envelope around that.
I caution against using Article 511 as a basis, unless you are willing to deal with NEC Section 511.7 and NFPA 30A as well.
Basically I’d suggest NFPA 497 as the starting point. You may also want to review NFPA 30 (Not 30A). It deals with determining "adequate ventilation."
Unless you are willing to do a fugitive emissions analysis (API RP500), I can say what you describe will be Class I, Division 1 from the lowest point up to the level where “adequate ventilation” occurs, with an additional 18” Division 2 envelope around that.
I caution against using Article 511 as a basis, unless you are willing to deal with NEC Section 511.7 and NFPA 30A as well.
Basically I’d suggest NFPA 497 as the starting point. You may also want to review NFPA 30 (Not 30A). It deals with determining "adequate ventilation."
thanx for all your help and effort...
If it weren?t for the term stationary I?d be all over NFPA 37? ?4.5.2 Engine rooms or other locations shall not be classified as hazardous locations as defined in Article 500 of NFPA 70, National Electrical Code, solely by reason of the engine fuel, lubricating oil, or hydraulic fluid.? With engines being frequently replaced (and sometimes run to destruction) 37 doesn't qualify itself for industrial testing activities. The area classification interpretation effort is now trudging down the fuel MIC ratios investigation to determine which type is driving MEP (mechanical, electrical, piping) design cost. I think hydrogen will be the worst case and perhaps a cost opinion or two will cause the 'any fuel any cell? project criteria to be revisited.
If it weren?t for the term stationary I?d be all over NFPA 37? ?4.5.2 Engine rooms or other locations shall not be classified as hazardous locations as defined in Article 500 of NFPA 70, National Electrical Code, solely by reason of the engine fuel, lubricating oil, or hydraulic fluid.? With engines being frequently replaced (and sometimes run to destruction) 37 doesn't qualify itself for industrial testing activities. The area classification interpretation effort is now trudging down the fuel MIC ratios investigation to determine which type is driving MEP (mechanical, electrical, piping) design cost. I think hydrogen will be the worst case and perhaps a cost opinion or two will cause the 'any fuel any cell? project criteria to be revisited.
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Of course, hydrogen introduces not only volatility issues (it can be self igniting under the right conditions), but it is lighter than air as well. That can radically alter the electrical area classification. I would definitely review NFPA 497.
NFPA 37 might have applied if you could show that the feed line disconnects would only release a very minor volume of fuel. Fugitive emission analysis might be valid in this case.
NFPA 37 might have applied if you could show that the feed line disconnects would only release a very minor volume of fuel. Fugitive emission analysis might be valid in this case.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Not to take the OP sideways, but knowing that most fuels are heavier then air that would make a pit classification very important, but with lighter then air fuels such as hydrogen would a pit still be classified? this part to me doesn't add up, as it would seem that a classification should be higher and include the ceiling if boxed in with lighter then air fuels?
Of course I'm thinking about the fuel in a gas form not a liquid, but thinking about it, if even in liquid form it still would expand to a gas, and maybe the whole area would need to be classified including the ceiling?
Sorry just trying to learn a little about this since this fuel might be in our future.
Of course I'm thinking about the fuel in a gas form not a liquid, but thinking about it, if even in liquid form it still would expand to a gas, and maybe the whole area would need to be classified including the ceiling?
Sorry just trying to learn a little about this since this fuel might be in our future.
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Yes, when hydrogen is the gas in question the classification goes up (as in thataway ^). The "standard" model in open air is basically a rounded top and bottom cylinder. From the point source a radius of 15' in all directions and then extended up from the point source 25'. If it is in an enclosed area the gas will fill the room in absence of adequate ventillation. These are just the "basics;" it can get more complicated depending on ventilation. See NFPA 497 or API RP500 for "standard figures."
From the OP's perspective both heavier and lighter than air must be considered.
From the OP's perspective both heavier and lighter than air must be considered.
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