CNG Station - Article 514 Requirements

[nhee2]

Table 514.3(B)(2) lists electrical classifications for areas around CNG dispensers. 514.8 lists requirements for underground conduit installation for areas beneath the areas classified by 514.3(B)(2). And exception 2 allows for PVC conduit if buried 24" deep, provided certain requirements for ells and EGC are met. Concrete encasement of the UG PVC conduit is not required.

There are other area classifications for a CNG facility which are defined by NFPA 52 but are not referenced in article 514 (for instance 15' from compression equipment). Would the requirements/exception of 514.8 also apply to these areas? Or would UG conduit in these Class I Div 2 areas be required to meet 501.10(A), which references 501.10(A)(1)(a) exception, allowing PVC underground, but only if concrete encased.

In other words, does NEC require CNG station UG PVC conduit to be concrete encased in classified areas around CNG processing (vs. dispensing) equipment?

I am looking at the 2014 handbook, although I think these sections are unchanged from 2011.

 

[rbalex]

... does NEC require CNG station UG PVC conduit to be concrete encased in classified areas around CNG processing (vs. dispensing) equipment?

No. Article 514 only applies to classifications created by dispensing sources. Other sources and their impact on wiring methods are not considered.

...
I am looking at the 2014 handbook, although I think these sections are unchanged from 2011.

If you have it available, compare 2002 NEC Section 514.8 AND Figure 514.3 with subsequent NEC editions. In 2005 the NFPA 30A Tech Committee had been restructured and it began to recognize the underground was not necessarily Division 1. They still wanted RMC as the basic wiring method but they have generally edged more toward "conventional" practices.

Also compare Table and Figure 514.3 between 2011 and 2014. There is a subtle but significant difference.

 

[nhee2]

No. Article 514 only applies to classifications created by dispensing sources. Other sources and their impact on wiring methods are not considered.

Rbalex,
Thanks. You said no, but then suggested 514 only applies to dispensing equipment (I think). It looks to me like processing (compressor) areas of a cng station would NOT be covered under 514.8. And 501.10 would apply to these areas. Am I interpreting your comment correctly?

I will take a look at the earlier code sections tomorrow.

 

[rbalex]

Rbalex,
Thanks. You said no, but then suggested 514 only applies to dispensing equipment (I think). It looks to me like processing (compressor) areas of a cng station would NOT be covered under 514.8. And 501.10 would apply to these areas. Am I interpreting your comment correctly?

I will take a look at the earlier code sections tomorrow.

Yes. Only locations classified because of the dispensing system is under consideration in Section 514.8.

Actually, Section 501.10(A)(1) Exception was originally developed for Sections 514.8 Exception No.2 and 515.8(A) since "conventional" area classification practices don't classify below grade. Since NFPA 30 and 30A, and NEC Articles 514 and 515 no longer treat below grade as automatically Division 1, Section 501.10(A)(1) Exception could probably be eliminated or modified.

NOTE: Concrete encasement is still common practice for PVC or RTRC if they are suitable for concrete encasement or direct burial in most refineries. Personally, I wouldn't be too concerned about below grade in most CNG applications.​