Can Overhead Wires Cross Over an Above Ground Storage Tank

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jbt260

Member
Location
Ohio
Occupation
Electrical Engineer
I would looking for some feedback on the following: Can you install an AST below overhead service wires (120/208V service, quadruplex wire)? The wire would be 15' above the tank. The tank has no dispenser. Article 514 applies since this is a fuel dispensing facility. The tank is for gasoline. My interpretation is that you cannot based on 514.7 and it's references. Any thoughts/opinions?

Thanks,
 

GoldDigger

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Location
Placerville, CA, USA
Occupation
Retired PV System Designer
511.7 (called out in 514.7) specifies rules for Class I locations without reference to the Division. Based on that, it looks like you are right.
But if the overhead service is existing, then you may already have a problem for possible Class I locations based on other tanks and facilities. A lot will depend on whether any existing tanks have dikes associated with them and those dikes extend anywhere under the wires.
You would have to determine just how far the Class I location boundary extends from existing equipment.
 

kwired

Electron manager
Location
NE Nebraska
We also get into whether or not the NEC even applies to these overhead conductors - especially if they are a service drop.

Now if NEC doesn't apply, other codes for the tanks and/or fuel storage components could still prohibit the tank or other equipment from being within certain distance or from being under the line altogether, but I don't know what specific code to apply here.
 

rbalex

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Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Without dispensing, the OP isn't in the scope of Article 514; however it is within the scope of Article 515 which has its own rules for wiring and equipment above classified locations. [Section 515.7] For all practical purposes of the OP, it's virtually the same as Section 511.7.

With respect to service conductors, most utilities apply the National Electrical Safety Code. Rule 127 Classified locations, references Articles 500 to 517 of the NEC. Sub-rule 127C Flammable liquid storage area references NFPA 30 which is the basis for Article 515.

Bottom line: AST over a Class I location is an unacceptable wiring method.
 
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