I work for a pipeline/crude oil storage facility. I have major heartburn over what to classify an area within our tank farm. According to 515 and the table, it doesn't tell us how to classify an underground installation with in the tank dike. To me, the area would be unclassified below grade, but I have others telling me that it's CL1 DIV 1. How is that possible when vapor and air don't exist underground? The area above the underground install is CL 1 DIV 2. Last but not least, how should the underground install be classified?
Classified of unclassified?
- Thread starter gerdes2j
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- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
This is one of those cases where the answer just isn't where you would expect it to be. You would think it would be in the Table 515.3 or at least in the Section on underground wiring (515.8) But it isn't in either one - see 515.9 instead.
Thanks for replying. I read 515.9 and that talks about seals. This article says that the installation should be considered to be a CL1 DIV1 install, but it doesn't state that the subgrade should be CL1 DIV1. Afterall, 515.8a states that you can use RNMC or a listed cable in a haz area. I am trying to figure out how to go about getting a classification of the subgrade whether it be a NEC reference or a NFPA reference. If you can provide me with that, I would have something to better research and provide to the powers above me!
DM2-Inc
Senior Member
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- Houston, Texas
You may want to take a look at API RP 500, 2002 edition. This has more information regarding tanks than the NEC.
The standard reads a lot like NFPA 70, Article 500 (may be where they got the name
)
The standard reads a lot like NFPA 70, Article 500 (may be where they got the name
)
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
I see no ambiguity. ?Considering? it to be Class I, Division 1 makes it Class I, Division 1. Think about this ? ALL electrical area classification is ?considering? the location to be whatever classification is determined.
As for the underground permissive for RNC, it is simply a recognizes it as a Division 1 wiring method under the conditions specified. It has been for years. When the API NEC Task Group first proposed the Exception to what is now 501.10(A)(1)(a) in the ?96 NEC, it was modeled after what is now 515.18 from the ?93 NEC. While it was often common practice at the time, why CMP14 felt the need memorialize 2? concrete encasement I don?t know since all tests proved the 2? cover alone was adequate.
How does considered make it be a CL1 DIV1 area? In reading 515.9, all it is stating is that the wiring method shall be considered a CL1 DIV1 install, not stating that it meets the requirements to be a CL1 DIV 1 install. Is the subgrade truly CL1 DIV1, or is it unclassified?
I guess in reading 515.8a, it talks about using a listed cable under at least 2' of cover. I have asked the AHJ in my area about using UF underground, and than bringing it up in RMC as it states in 515.8a. Afterall, UF is listed for an underground installation. We would be bringing it up in RMC from the lowest point below grade, and then through a sealoff. Would this be an acceptable wiring method? They said it would be legal according to the code, and I am just looking for a second opinion on the matter to reassure that it would be acceptable, or if they over looked something.
I'm not doubting your knowledge of the subject matter, but looking for an honest second opinion before we do something illegal and then pay for it later. If the code were to just spell out the classification of this area in the table, it would make life a lot easier on us field personnel. Afterall, they spell UG installs out for other classified areas in the code!
I guess in reading 515.8a, it talks about using a listed cable under at least 2' of cover. I have asked the AHJ in my area about using UF underground, and than bringing it up in RMC as it states in 515.8a. Afterall, UF is listed for an underground installation. We would be bringing it up in RMC from the lowest point below grade, and then through a sealoff. Would this be an acceptable wiring method? They said it would be legal according to the code, and I am just looking for a second opinion on the matter to reassure that it would be acceptable, or if they over looked something.
I'm not doubting your knowledge of the subject matter, but looking for an honest second opinion before we do something illegal and then pay for it later. If the code were to just spell out the classification of this area in the table, it would make life a lot easier on us field personnel. Afterall, they spell UG installs out for other classified areas in the code!
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
I?m sorry, but you just aren?t going to find what you?re looking for specifically if you won?t accept the reference to Section 515.9. Article 510 has an overall Scope authority over Articles 511 through 517. The last sentence of Section 510.2, as well as 90.4 in general, should be adequate substantiation for accepting your AHJ?s opinion.
I have pointed out in several previous threads that, outside of Articles 511 through 516, the NEC doesn?t give substantial direction for classifying ANY location; and the area classification material provided in those Articles is extracted from some another NFPA Code or Standard. The FPNs located just after each Article?s Title or Scope statement identify the other NFPA referenced documents. If you roll the clock back through a few of the previous NEC editions, it will indicate the referenced documents have changed occasionally. All other electrical area classification reference documents, such as NFPA 497 or API RP 500, while usually accepted as authoritative, are Recommended Practices at most. Outside Articles 511 - 516, electrical area classification is essentially the judgment call of someone qualified to make it.
With respect to wiring methods in Article 511-516, the same may be said but to a much lesser extent. The most recent referenced NFPA Codes and Standards that are the basis for extracted material in NEC Articles 511-517 rarely include specific wiring requirements and either refers to Art 501 or to the NEC in general for installation practices. Occasionally, they may also include other electrical related issues such as controls or lightning protection relevant to their specific subject matter.
NFPA 33, 34 and 409, do make specific reference to their respective ?extracted? Articles (516, 516 and 513); however, of those three, only Article 513 includes wiring methods substantially beyond those already required in Article 501 or other relevant parts of the Code.
For the most part, the more restrictive wiring methods in Articles 511-517 are residue from much older versions of their original reference standards. If you want it cleaned up, make a Proposal for the ~2014 NEC.
I have pointed out in several previous threads that, outside of Articles 511 through 516, the NEC doesn?t give substantial direction for classifying ANY location; and the area classification material provided in those Articles is extracted from some another NFPA Code or Standard. The FPNs located just after each Article?s Title or Scope statement identify the other NFPA referenced documents. If you roll the clock back through a few of the previous NEC editions, it will indicate the referenced documents have changed occasionally. All other electrical area classification reference documents, such as NFPA 497 or API RP 500, while usually accepted as authoritative, are Recommended Practices at most. Outside Articles 511 - 516, electrical area classification is essentially the judgment call of someone qualified to make it.
With respect to wiring methods in Article 511-516, the same may be said but to a much lesser extent. The most recent referenced NFPA Codes and Standards that are the basis for extracted material in NEC Articles 511-517 rarely include specific wiring requirements and either refers to Art 501 or to the NEC in general for installation practices. Occasionally, they may also include other electrical related issues such as controls or lightning protection relevant to their specific subject matter.
NFPA 33, 34 and 409, do make specific reference to their respective ?extracted? Articles (516, 516 and 513); however, of those three, only Article 513 includes wiring methods substantially beyond those already required in Article 501 or other relevant parts of the Code.
For the most part, the more restrictive wiring methods in Articles 511-517 are residue from much older versions of their original reference standards. If you want it cleaned up, make a Proposal for the ~2014 NEC.
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