Re: Motor fuel dispensing facilities
I must admit what threw me was that you did a verbatim quote for 514.9(A) but you “free-styled” 505.16(A)(2). I realize the correct reference was 505.16(B)(2) and you may want to re-read it. BTW are you really installing to a Zone rather than Division classification system?
In any case, using 505.16(B) (2) indicates the enclosures under consideration are Division “explosion-proof” rather than Zone protection type “d” or “e.” In this case only arcing, sparking, or heat producing (ASH) devices are considered unless the conduit is 2” or largerand the enclosure contains terminals, splices, or taps. Even if the seal is required because of one of these conditions and not otherwise exempted through an exception it still can be as much as 18” from the enclosure. The required boundary seal may be as much as 10’ from the boundary. In other words, the enclosure seal and the boundary seal may, in fact, be the same seal.
BTW in this application gases will get into the conduit – period. (They will get into the explosion-proof enclosures too.) However, if everything is sealed properly there will be no ready source of ignition (no ASH) in the raceway. Conductors properly sized will not generate enough heat to ignite the gases in this application, which are typically Group D (or IIA if you’re using Zones).
[ May 26, 2004, 03:26 PM: Message edited by: rbalex ]
Robert B. Alexander, P.E.
"I know that you believe you understand what you think the NEC says, but I am not sure you realize that what you read is not what it means." (Corollary to Charlie's Rule)