 |
Figure 01
|
For EC&M Magazine
By Mike Holt, NEC® Consultant
Do you know the rules for fuels?
Article 511 applies to areas used for the service and repair operations of self propelled vehicles that use volatile flammable liquids or flammable gases. Figure 01. Examples include passenger automobiles, buses, trucks, and tractors. If there's any fuel dispensing in the building, the requirements of Article 514 also apply.
Installations within the scope of Article 511 include automobile service/repair centers, service/repair garages for commercial and/or fleet vehicles, and shops that service motorcycles and all terrain vehicles (ATVs).
Areas adjacent to classified locations aren't classified if mechanically ventilated at a rate of four or more air changes per hour, or when walls or partitions effectively cut off the adjacent area [511.3(E)].
Wiring and equipment
Wiring and equipment within a Class I location must be installed per Article 501 [511.4(A) and (B)].‚ Fuel dispensing units within buildings must comply with Article 514 [511.4(B)(1)].
The lamp and flexible cord of portable lighting equipment must be supported or arranged in such a manner that it can't be used in a hazardous (classified) location [511.4(B)(2)], or it must be identified for a Class I, Division 1 location [501.130(B)].
Fixed wiring above a Class I hazardous (classified) location must be in raceways, unless it is one of the following [511.7(A)(1)]:
• Type AC, MC, or MI cable.
• Part of a manufactured wiring systems.
• PLTC cable per Article 725.
Pendant cords above a Class I hazardous (classified) location must be suitable for the type of service and listed for hard usage per Table 400.4 [511.7(A)(2)].
Equipment with make and break contacts installed less than 12 ft above the floor level (excluding receptacles, lamps, and lampholders) must be of the totally enclosed type or constructed to prevent sparks or hot metal particles from escaping [511.7(B)(1)(a)].
Lampholders and lamps for fixed lighting over travel lanes or where exposed to physical damage must be at least 12 ft above floor level, unless the luminaires are of the totally enclosed type or constructed to prevent sparks or hot metal particles from escaping [511.7(B)(1)(b)].
Underground wiring below a commercial garage must be installed in threaded rigid metal conduit or intermediate metal conduit. Ex: PVC, Type RTRC conduit, and Type HDPE conduit can be installed below a commercial garage if buried under at least 2 ft of cover. Threaded rigid metal conduit or threaded intermediate metal conduit must be used for the last 2 ft of the underground run. An equipment grounding conductor per Article 250 is required within the raceway [511.8].
Raceway, cable, and boundary seals must be installed per 501.15, and applied to both horizontal and vertical boundaries of the defined Class I locations [511.9]. If the Class I, Division 1 boundary is beneath the ground, the sealing fitting can be installed after the raceway leaves the ground. However, there must not be any unions, couplings, boxes, or fittings (except explosionproof reducing bushings) between the seal fitting and the point where the raceway leaves the earth's surface [501.15(A)(4) Ex 2].
Fuel dispensing facilities
The portion of a facility where fuel is stored and dispensed into the fuel tanks of motor vehicles and marine craft, or into approved containers, must comply with Article 514.
What's most striking about Article 514 is the large table that makes up about half of it. This table doesn't provide any electrical requirements, list any electrical specifications, or address any electrical equipment. What this table tells you is how to classify a motor fuel dispensing area based on the equipment contained therein.
Classification of locations
Figure 514.3 in the NEC shows an example of a typical Class I, Division 1 and 2 location. These areas and dimensions are described in greater detail in Table 514.3(B)(1).
If the authority having jurisdiction is satisfied that flammable liquids having a flash point below 100 DegrF [Article 100 Volatile Flammable Liquid] won't be handled, such locations can be unclassified [514.3(A)].
Table 514.3(B)(1) is to be used to classify motor fuel dispensing facilities and commercial garages as defined in 511.2 where a flammable liquid having a flash point below 100 DegrF is stored, handled, or dispensed. A Class I location doesn't extend beyond an unpierced wall, roof, or other solid barrier [514.3(B)].
Wiring and equipment
Electrical wiring and equipment serving fuel dispensing locations in marinas and boatyards must be installed on the side of the wharf, pier, or dock opposite from the fuel piping system [514.3(C)(1)].
Is the construction of piers, wharfs, or docks open? If so, the area 18 in. above the surface of the dock, pier, or wharf and extending 20 ft horizontally in all directions from the outside edge of the dispenser and down to the water level is considered a Class 1, Division 2 location [514.3(E)(1)].
Electrical equipment and wiring within a Class I location, as defined in Table 514.3(B)(1), must comply with Article 501. This means you must use threaded rigid metal conduit and/or threaded intermediate metal conduit for fixed wiring. But PVC conduit is permitted underground per 514.8 [514.4].
Wiring above a Class I location, as defined in Table 514.3(B)(1), must be installed within a raceway, or in Type AC, MC, MI, PLTC, or TC cable [511.7(A)(1)].
Fixed lighting over travel lanes, or if exposed to physical damage, must be at least 12 ft above floor level, unless the luminaire is of the totally enclosed type or constructed to prevent sparks or hot metal particles from escaping [511.7(B)].
Underground wiring beneath a classified location must be installed in threaded rigid metal conduit or threaded intermediate metal conduit. Electrical conduits located below the surface of a Class I, Division 1 or 2 location, as identified in Table 514.3(B)(1) and Table 514.3(B)(2), must be sealed within 10 ft of the point of emergence above grade [514.8].‚
Except for listed explosionproof reducers at the raceway seal fitting, there must be no union, coupling, box, or fitting between the raceway seal fitting and the point of emergence above grade.
Ex 2: PVC, Type RTRC conduit, and Type HDPE conduit can be installed below a classified location if buried under at least 2 ft of cover. Threaded rigid metal conduit or threaded intermediate metal conduit must be used for the last 2 ft of the underground run. An equipment grounding conductor per Article 250 is required within the raceway.
Raceway seal
A listed raceway seal must be installed in each raceway that enters or leaves a dispenser. The raceway seal fitting or listed explosionproof reducer at the seal must be the first fitting after the raceway emerges from the earth's surface or concrete [514.9(A)].
A raceway seal fitting that complies with 501.15 must be installed in each raceway run that leaves a Class I location and applies to both horizontal and vertical boundaries of the defined Class I location [514.9(B)].
If the boundary is beneath the ground, the sealing fitting can be installed after the raceway leaves the ground, but there must be no union, coupling, box, or fitting, other than listed explosionproof reducers at the sealing fitting in the raceway between the sealing fitting and the point at which the raceway leaves the earth's surface [501.15(A)(4) Ex 2].
Disconnects
These four requirements are new with the 2017 NEC:
1. Fuel dispensing systems must have clearly identified emergency shutoff devices or disconnects installed at approved locations at least 20 ft and not more than 100 ft from the fuel dispensing devices they serve [514.11(A)].
2. Emergency shutoff devices or disconnects must disconnect power to all dispensing devices; to all remote pumps serving the dispensing devices; to all associated power, control, and signal circuits; and to all other electrical equipment in the hazardous (classified) locations surrounding the fuel dispensing devices [514.11(A)].
3. Attended self service stations must have an emergency dispenser disconnect that's readily accessible to the attendant [514.11(B)].
4. At unattended motor fuel dispensing facilities, the disconnects must be readily accessible to patrons and at least one additional disconnect must be readily accessible to each group of dispensing devices on an individual island [514.11(C)].
Dispensing with Code Violations
How can you prevent code violations, when the rules for fuels seem so complex? The core strategy of Articles 511 and 514 is to keep fuel and ignition sources apart from each other. In your design review, identify the ignition sources and see what Articles 511 and 514 have to say about isolating them from the fuel.
|
