511.7 Fixed Wiring Above Class I Locations.
Code Change Summary: Existing requirements made into a list for ease of use.
In the 2023 NEC®, the wiring methods permitted for use as fixed wiring above hazardous locations in commercial repair garages has been reformatted into a list as suggested in the NEC® Style Manual,
A list of approved wiring methods aligns with Section 3.3.2 of the NEC® Style Manual which suggests the use of lists or tables rather than long text descriptions.
The classification of a commercial repair garage is determined based on several considerations including:
- Whether the garage is a “major” or “minor” repair garage
- If the garage includes fuel dispensing
- If vehicles using Class I liquids or heavier-than-air gaseous fuels (such as LPG) are repaired
- If vehicles using lighter-than-air gaseous fuels (such as hydrogen and natural gas) are repaired or stored
Areas of a commercial repair garage that are adjacent to classified locations where flammable vapors are not likely to be released, such as supply rooms, electrical rooms, or similar locations, are considered unclassified where separated by an unpierced wall, roof, or other solid partition, or where designed with positive air pressure and mechanical ventilation at a rate of four or more air changes per hour.
The new list of wiring methods created in Section 511.7(A)(1) includes:
(1) RMC, IMC, or EMT, all with listed fittings.
(2) Rigid PVC, RTRC, or ENT.
(3) FMC, LFMC, or LFNC, all with listed fittings.
(4) MC cable, AC cable, TC cable, or TC-ER cable, all with listed fittings.
(5) MI cable with listed fittings.
(6) Manufactured wiring systems.
(7) PLTC cable or Type PLTC-ER cable.
(8) ITC cable or ITC-ER cable with listed fittings.
(9) Cellular metal floor raceways or cellular concrete floor raceways only for supplying ceiling outlets or extensions to the area below the floor.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2023 NEC® edition of NFPA 70.
2020 Code Language:
511.7(A)(1) Fixed Wiring Above Class I Locations. All fixed wiring above Class I locations shall be in metal raceways, rigid nonmetallic conduit, electrical nonmetallic tubing, flexible metal conduit, liquidtight flexible metal conduit, or liquidtight flexible nonmetallic conduit, or shall be Type MC, AC, MI, manufactured wiring systems, or PLTC cable in accordance with Article 725, or Type TC cable or Type ITC cable in accordance with Article 727. Cellular metal floor raceways or cellular concrete floor raceways shall be permitted to be used only for supplying ceiling outlets or extensions to the area below the floor, but such raceways shall have no connections leading into or through any Class I location above the floor.
2023 Code Language:
511.7(A)(1) Fixed Wiring Above Hazardous (Classified) Locations. Fixed wiring above hazardous (classified) locations shall be permitted to be one or more of the following:
(1) Rigid metal conduit (RMC) or intermediate metal conduit (IMC) with listed threaded or threadless fittings, or electrical metallic conduit (EMT) with listed fittings.
(2) Rigid polyvinyl chloride conduit (PVC), reinforced thermosetting resin conduit (RTRC), or electrical nonmetallic tubing (ENT).
(3) Flexible metal conduit (FMC), liquidtight flexible metal conduit (LFMC), or liquidtight flexible nonmetallic conduit (LFNC), with listed fittings.
(4) Type MC cable, Type AC cable, Type TC cable, or Type TC-ER cable, including installation in cable trays. Type TC-ER cable shall include an equipment grounding conductor (EGC) in addition to any drain wire. All cable types shall have listed fittings.
(5) Type MI cable terminated with listed fittings and supported in a manner to avoid tensile stress.
(6) Manufactured wiring systems.
(7) Type PLTC cable or Type PLTC-ER cable in Class I, Class 2, or Class 3 circuits. Type PLTC-ER cable shall include an equipment grounding conductor (EGC) in addition to any drain wire.
(8) Type ITC cable or Type ITC-ER cable in accordance with 335.4 and 335.5, terminated with listed fittings. Type ITC-ER cable shall include an equipment grounding conductor (EGC) in addition to any drain wire.
(9) Cellular metal floor raceways or cellular concrete floor raceways only for supplying ceiling outlets or extensions to the area below the floor. Such raceways shall have no connections leading into or through any Class I location above the floor.