#1Where 501.15(B)(2) exception does not apply

[Chris Hunter]

Re:2005 Nec Class 1 locations Article 501.10(B)(1)(1) allows Class 1 Division 1 wiring methods to be employed in Class 1 Division 2 locations. 501.10(B)(1)(a) Exception permits PVC under the stated conditions. The required concrete encasment is permited to be omited "where subject to the provisions of 514.8." The provisions of Article 514.8. indicates any potion of electrical wiring that is below a Class 1 Division 2 location [as classified in table 514.3(B)(1)] shall be sealed within 10 feet of the point of emergence above grade. Table 514.3(B)(1) speaks to service rooms without dispensing yet the extent of the classified location listed does not referance the 18" class 1 division 2 location associated with commercial Garages 511.3(B)(3)(1). I have read a Code Basic article indicating "If a raceway enters a classified location, the underfloor location takes on the classification of the area above, even if the conduit passes unbroken through the area and terminates in an unclassified location". Question #1- In a Commercial Garage Service Room when 4 Air changes is not provided 511.3 (B)(3)(1) and where PVC is used 2 foot below the classified area and Rigid Steel is stub up and passes through the 18" classified area and extends another 12" and terminates in a non classified area does 501.15(B)(2) exception #1 permit termination to be unsealed or does the exception per 514.8. superceed the exception and require sealed terminations? Question #2- Would concrete encasing the PVC sections remove 514.8. sealing requirment. Question #3- Would the below slab Rigid conduit coupling need to extend into the below slab concrete encasment required?

 

[rbalex]

I would really like to see the source of that ?Code Basic? article.

Nevertheless,

Question #1:

You didn?t specify whether the PVC was encased or not. I will assume it isn?t from your second question. Here?s the deal: in absence of dispensing the underground isn?t classified or considered classified, so 501.15(B)(2) Exception No. 1 applies.

Both Article 511 and 514 have material extracted from NFPA 30A. The 30A Technical Committee (TC) occasionally stepped on Code Making Panel 14?s (CMP14) toes. Until the 2003 Edition, the 30A TC specified that the underground be treated as if it were Division 1. There is no common coordinating committee so it often takes a few cycles of both documents to ?re-coordinate? them.

Question #2:

It would make no difference.

Question #3:

No

 

[Chris Hunter]

I would really like to see the source

I would really like to see the source

http://ecmweb.com/mag/electric_wiring_commercial_garages/

Digging a bit deeper I now realize the 2002 NEC changed in 2005 with respect to 511.4(A)(1). Article is dated 2003 therefore oviously not referancing 2005 NEC. Correct me if in error but the 2002 NEC classified the area below a class 1 div 2 as class 1 when a conduit penatrated the slab, perhaps mandating conduit seals depicted in the referanced article, and the 2005 NEC now considers the area below class 1 div 2 associated with 511 as unclassified.

Thanks in advance.
Perhaps M Holt ECM shouldconsider pulling and/or updating old article?

 

[rbalex]

Another history lesson

I reviewed Mike’s “Code Basics” article and, as long as we understand the context is Article 511 of the 2002 NEC, the quote that troubled me is correct. It should be noted that the Art 511 text that justified the quote troubled several members of the API NEC Task Force for years – it just didn’t fit the generally acknowledged principals of electrical area classification.

You already picked up on one major point; there were several significant changes between the 2002 and 2005 NECs in Article 511. One of the easiest to see is the FPN after the Article’s title. The 2002 NEC cites NFPA 88B-1997 as the source of extracted material; the 2005 NEC cites NFPA 30A-2003. NFPA 88B-1997 was integrated into NFPA 30A. That also changed the TC.

Other than Article 514, where NFPA 30A is also the source of extracted text, there has never been a mandated underground classification. Before 2005, the common text was:

Any portion of electrical wiring or equipment that is below the surface of a Class I, Division 1, or a Class I, Division 2 location [as classified in Table xxx] shall be considered to be in a Class I, Division 1, location that shall extend at least to the point of emergence above grade.

Note it didn’t actually say it was Division 1, only that it was considered to be.

Again in 2003, the NFPA 30A TC revised content that had previously been in NFPA 88B. The current text is

514.8 Underground Wiring. Underground wiring shall be installed in threaded rigid metal conduit or threaded steel intermediate metal conduit. Any portion of electrical wiring that is below the surface of a Class I, Division 1, or a Class I, Division 2, location [as classified in Table 514.3(B)(1) and Table 514.3(B)(2)] shall be sealed within 3.05 m (10 ft) of the point of emergence above grade.

Also compare Figure 514.3 in the 2002 and earlier with 2005 and later.

Historically, the underground has generally been unclassified.



Notes:

1. While CMP 14 maintains jurisdiction over Articles 511 and 514, the NFPA 88A and NFPA 30A TCs still have considerable influence on them, both through formal Proposals and informal contacts.
2. What is now 501.10(A)(1)(a) Exception was first introduced in 1996. But the concept was drawn from NEC 1993, Section 515-5(a). The difference was that CMP 14 decided to add the concrete envelope – which messed up Articles 514 and 515. So the exceptions to the Exception were added in 1999.

I’m not sure why CMP 14 felt the need for the envelope other than it was common practice for duct banks in refineries.
​

 

[Chris Hunter]

Article (Fig 4&5)

Article (Fig 4&5)

If I understand completely per 2005 NEC, GRC or IMC raceways routed vertically and passing completely through without coupling (etc) to a point not less than 12" below and 12" above boundaries associated with the 18" Class 1 Div 2 area within non-fuel (Gasoline or otherwise) dispensing major commercial repair facilitates who will service Gasoline type vehicle fuel tanks and perhaps fuel pumps A) Does not required RNC extensions of these raceways to be installed with 2 feet of cover below the floor. B) Conduit seals above the class 1 area are not required per 501.15 (B)(2) by exception since the raceway stub up floor exceeds 30 inches. C) Rigid raceways are not required at the other end of the run where under slab conduit turned up if emerging and terminating in an adjacent unclassified area. This does not appear to support Fig 4&5 of the referenced article depicting Steel raceways, conduit seals, 2 ft of cover.

Side bar: I don't see where a Nema 1 or 3R enclosure would be considered totally enclosed meeting 511.7(B)(1)(a) so or are we talking Nema 4,12 etc.

Thanks very much in advance.

 

[rbalex]

This is like differential equations. My brother used to say it was the branch of mathematics where you were given an answer first and then you had to figure out what the original problem was.

Most of the answer though is understanding which Article or Section of the NEC applies. Part of the problem lies with the fact that you are dealing with the 2005 NEC and referencing an article based on the 2002 NEC. The 2008 NEC is much clearer.

I believe I mentioned that the root reference document for Art 511 is now NFPA 30A rather than NFPA 88B. Two important things happened; one, the content of 88B was absorbed into 30A and two, even more important, was the content came under the jurisdiction of an entirely different TC. What I failed to mention is the 30A TC apparently also went through a major restructuring which resulted in a view of electrical design and installation more in line with Code Making Panel 14. A lot of the “problem” content in both Articles is residual and no longer in NFPA 30A.

However, it is vitally important to recognize that, once dispensing comes into the picture, so does Article 514.

For analysis though, we will assume that your scenario does not include dispensing but transfers are possible; so the classification of the area of concern is Class I, Division 2 per 511.3(B)(3)(1). Under those conditions:

1. The minimum raceway cover is only that otherwise required by Section 300.5.
2. Seals may be ommited per 501.15 (B)(2), Exception No. 1.
3. The terminus in an unclassified location does not require a seal. Figures 4 & 5 of the referenced article were based on the 2002 NEC. The rules were different (and unnecessary) then – but they were the rules.

Sidebar: It is something of a judgment call since the NEMA 250 descriptive definitions for enclosures in non-hazardous locations is based totally on various degrees of preventing external media from entering not exiting the enclosure. There a several NEMA Type 1 or 3R enclosures that would be effective in preventing the products of arcing from escaping.