2017 NEC 514.8

[stevenje]

I am doing a plan review for a new LPG dispensing unit at an existing gas station. There are existing underground conduit runs for sign lighting and pole lighting that run under the Class I Div I area of the new dispensing tank, that start and stop in unclassified areas. The 2017 NEC 514.8 code indicates that it is a Class I Div I area. I have seen some conflicting information that says it is an unclassified area. Any thoughts or comments would be appreciated.

 

[rbalex]

A careful reading of Section 514.8 and the cross-referenced Tables in 515.3(B)(1) and (2) will indicate that Division 1 locations underground are very limited. In fact, Section 514.8 itself doesn't require the underground to be classified at all. However, what it does require, is that raceways below any aboveground classified location must be threaded RMC or IMC (unless one of the Exceptions apply) AND such raceways (Exception or not) "...shall be sealed within 3.05 m (10ft) of the point of emergence above grade."

By the general rules of electrical area classification, unless a pit is involved, below grade is not classified. This is born out by the current Figures 514.3(A) and (B). In NEC Editions 2002 and earlier, the Figures indicated some portions of the underground were Classified Division 1. (This is what I had to look up and the reason for my delay in answering)

 

[stevenje]

A careful reading of Section 514.8 and the cross-referenced Tables in 515.3(B)(1) and (2) will indicate that Division 1 locations underground are very limited. In fact, Section 514.8 itself doesn't require the underground to be classified at all. However, what it does require, is that raceways below any aboveground classified location must be threaded RMC or IMC (unless one of the Exceptions apply) AND such raceways (Exception or not) "...shall be sealed within 3.05 m (10ft) of the point of emergence above grade."

By the general rules of electrical area classification, unless a pit is involved, below grade is not classified. This is born out by the current Figures 514.3(A) and (B). In NEC Editions 2002 and earlier, the Figures indicated some portions of the underground were Classified Division 1. (This is what I had to look up and the reason for my delay in answering)

Thank you for the response. If I understand you correctly, you need to install a seal-off at each end of a conduit run in accordance to 514.8. For example, a conduit run from one light pole to another light pole that in installed under the Class I Div 2 area.

I am assuming that the two seal off locations would be considered "boundary" locations and be installed per 514.9(B) which refers to 501.15(B)(2) in this situation.

In my case, it should be interesting trying a figure out how the existing light pole(s) and signage underground conduit runs were installed.

Thanks again.

 

[rbalex]

The raceways must indeed be sealed at both ends.

Articles 511 to 515 are special cases and not completely under the control of NEC Code Making Panel 14 (CMP14). An Informational Note (IN) after the title of each Article will note that much of the content is extracted from another external NFPA Standard. (NFPA 30A in Article 514's case) CMP14 only edits the content to make it consistent with the rest of the relevant Chapter 5 material. Historically, Arts 511 to 515 are the only installation applications where the area classification can actually be determined directly from the NEC. Other applications need an external standard such as NFPA 497 or API RP 500 to evaluate the area classification. (See Section 500.4(B) for other examples.)

Occasionally, there is some residual effect from earlier external standards. Currently, as noted in my previous response, the underground is not usually classified except for a few limited cases; therefore, a Section 514.9 "boundary" may not actually exist. Nevertheless, seals must be installed at both ends of a below grade raceway that is beneath any Section 514.3 above grade classified location. Even previously, when an underground location was classified, Section 501.15(C)(1) requires the seal to be accessible so grade became the effective "boundary".

 

[stevenje]

The raceways must indeed be sealed at both ends.

Articles 511 to 515 are special cases and not completely under the control of NEC Code Making Panel 14 (CMP14). An Informational Note (IN) after the title of each Article will note that much of the content is extracted from another external NFPA Standard. (NFPA 30A in Article 514's case) CMP14 only edits the content to make it consistent with the rest of the relevant Chapter 5 material. Historically, Arts 511 to 515 are the only installation applications where the area classification can actually be determined directly from the NEC. Other applications need an external standard such as NFPA 497 or API RP 500 to evaluate the area classification. (See Section 500.4(B) for other examples.)

Occasionally, there is some residual effect from earlier external standards. Currently, as noted in my previous response, the underground is not usually classified except for a few limited cases; therefore, a Section 514.9 "boundary" may not actually exist. Nevertheless, seals must be installed at both ends of a below grade raceway that is beneath any Section 514.3 above grade classified location. Even previously, when an underground location was classified, Section 501.15(C)(1) requires the seal to be accessible so grade became the effective "boundary".

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