Questions and Answers
Article 501 covers the requirements for electrical and electronic equipment and wiring for all voltages in Class I locations where fire or explosion hazards may exist due to flammable _____.
gases, vapors, liquids
Wiring methods and materials permitted in Class I, Division 1 locations include _____.
threaded rigid metal or threaded steel IMC, flexible fittings listed for Class I, Division 1 locations, boxes approved for Class I, Division 1 locations
Type PVC conduit, Type RTRC conduit, and Type HDPE conduit shall be permitted in Class I, Division 1 underground locations where encased in a concrete envelope a minimum of _____ in.thick and provided with not less than _____ in.of cover measured from the top of the conduit to grade.
2, 24
MI cable terminated with fittings listed for the location is allowed in Class I, Division 1 locations.
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In industrial establishments with restricted public access where only qualified persons will service the installation, MC-HL cable is allowed to be used in a Class I, Division 1 location if it _____ and terminated with fittings listed for the application.
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When necessary to employ flexible connections in a Class I, Division 1 location, such as at motor terminals, flexible fittings listed for the location or flexible cord in accordance with 501.140 are permitted if terminated with cord connectors listed for the location.
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When necessary to employ flexible connections in a Class I, Division 1 location, such as at motor terminals, _____ shall be permitted.
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Wiring methods permitted in Class I, Division 1 locations are permitted in Class I, Division 2 locations.
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_____ is(are) among the wiring methods permitted within a Class I, Division 2 location.
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In Class I, Division 2 locations, where metal conduit will not provide sufficient corrosion protection, _____ shall be permitted.
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In a Class I, Division 2 location, if flexibility is necessary, _____ are some of the wiring methods that are permitted.
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When provisions for flexibility are necessary in Class I, Division 2 locations, FMC with listed fittings can be used.
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In a Class I, Division 2 location, switches and circuit breakers shall be installed in explosionproof enclosures meeting the requirements for Class I, Division 1 locations.
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General-purpose enclosures and fittings are permitted in Class I, Division 2 locations unless the enclosure contains make-and-break contacts for _____ as required by 501.105(B)(2), 501.115(B)(1), and 501.150(B)(1).
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In Class I hazardous (classified) locations, sealing compound shall be used in Type MI cable termination fittings to _____.
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In Class I, Division 1 locations, seals shall not be required for conduit entering an enclosure if the switch, circuit breaker, fuse, relay, or resistor is _____.
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Class I, Division 1 conduit seals shall be installed within _____ in.of the enclosure in each conduit entry into a pressurized enclosure where the conduit is not pressurized as part of the protection system.
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In Class I, Division 1 locations, conduit seals entering pressurized enclosures shall be installed within _____ in.from the enclosure or as required by the enclosure marking.
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Where two or more explosionproof enclosures that require conduit seals are connected by nipples or runs of conduit not more than _____ in.long, a single conduit seal in each such nipple connection or run of conduit shall be considered sufficient if the seal is located not more than 18 in.from either enclosure.
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A conduit run between a conduit seal and the point at which the conduit leaves a Class I, Division 1 location shall contain no union, coupling, box, or other fitting except for a listed _____ reducer installed at the conduit seal.
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A sealing fitting shall be permitted to be installed within _____ ft of either side of the boundary where a conduit leaves a Class I, Division 1 location.
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Where the Class I, Division 1 location boundary is below grade, a sealing fitting shall be permitted to be installed _____, and there shall not be any unions, couplings, boxes, or fittings between the sealing fitting and the grade, other than listed explosionproof reducers.
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A conduit seal shall be required in each conduit run leaving a Class I, Division 2 location. The conduit sealing fitting shall be installed on either side of the boundary within _____ ft of the boundary.
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A sealing fitting shall not be required if a metal conduit passes completely through a Class I, Division 2 location if the termination points of the unbroken conduit are located in unclassified locations and it has no fittings less than _____ in.of either side of the boundary of the hazardous (classified) location.
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When sealing fittings are required for Class I locations, they shall comply with which of the following rule(s)?
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The minimum thickness of sealing compound in Class I locations shall not be less than the trade size of the conduit or sealing fitting and, in no case, shall the thickness of the compound be less than _____ in.
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The cross-sectional area of the conductors or optical fiber tubes permitted in a sealing fitting shall not exceed _____ percent of the cross-sectional area of RMC of the same trade size.
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In Class I, Division 1 locations, seals for cables at all terminations shall be installed within _____ in.of the enclosure or as required by the enclosure marking.
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In Class I, Division 1 locations, seals for cables at terminations, only explosionproof unions, couplings, reducers, elbows, and capped elbows that are not larger than the _____ of the conduit shall be permitted between the sealing fitting and the enclosure.
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When installing shield cables and twisted-pair cables in conduit in a Class I, Division 1 hazardous (classified) location, the removal of shielding material or the separation of the twisted pairs of shielded cables and twisted pair cables isn't required within the conduit seal fitting.
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Each multiconductor cable installed in conduit in a Class I, Division 1 location shall be considered as a single conductor if the cable is incapable of transmitting _____ through the cable core.
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The removal of shielding material or the separation of the twisted pairs of shielded cables and twisted pair cables isn't required within the conduit seal fitting in a Class I, Division 2 hazardous (classified) location provided the termination is by an approved means to minimize the entrance of gases or vapors and prevent flame propagation.
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In Class I locations, the locknut-bushing and double-locknut types of contacts shall not be depended on for bonding purposes.
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When FMC or LFMC is used as permitted in Class I, Division 2 locations, it shall include an equipment bonding jumper of the wire type in compliance with 250.102.
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Circuit breakers in Class I, Division 2 locations that are not hermetically sealed or oil-immersed shall be installed in a Class I, Division 1 enclosure.
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Motors, generators, or other rotating electrical machinery identified for Class I, Division 2 locations can be used in Class I, Division 1 locations.
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Totally enclosed motors of the types specified in 501.125(A)(2) or (A)(3) shall have a device to de-energize the motor or provide an alarm if there is any increase in temperature of the motor beyond designed limits when operating in Class I, Division 1 locations.
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Luminaires installed in Class I, Division 1 locations shall be identified as a complete assembly for the Class I, Division 1 location and shall be clearly marked to indicate the _____ for which it is identified.
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Luminaires installed in Class I, Division 1 locations shall be protected from physical damage by a suitable _____.
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Pendant luminaires in a Class I, Division 1 location shall be suspended by and supplied through threaded rigid metal conduit stems or threaded steel intermediate conduit stems, and threaded joints shall be provided with _____ or other effective means to prevent loosening.
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Boxes, box assemblies, or fittings used to support luminaires in Class I, Division 1 locations shall be identified for Class I locations.
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Luminaires installed in Class I, Division 2 locations shall be protected from physical damage by a suitable _____.
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In Class I, Division 1 locations, all utilization equipment shall be _____ for use in a Class I, Division 1 location.
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Flexible cords are not permitted in Class I locations.
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Flexible cords in Class I hazardous (classified) locations shall _____.
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In Class I, Division 1 or Division 2 locations where the boxes, fittings, or enclosures are required to be explosionproof, if a flexible cord is used it shall terminate with a cord connector or attachment plug listed for the location, or a listed cord connector installed with a seal that is listed for the location. In Division 2 locations where explosionproof equipment is not required, the cord shall terminate _____.
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For Class I locations where 501.140(A)(5) is applied, flexible cords shall be _____ from the power source to the temporary portable assembly and from the temporary portable assembly to the utilization equipment.
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In Class I locations, attachment plugs shall be of the type providing for _____ a permitted flexible cord and shall be identified for the location.
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In Class I, Division 1 locations, all apparatus and equipment of signaling, alarm, remote-control, and communications systems _____ shall be identified for Class I, Division 1 locations.
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Study Notes
Class 1 Hazardous Locations Overview
- Article 501 outlines requirements for electrical equipment and wiring in Class I hazardous locations where flammable gases, vapors, or liquids may be present.
- Class I locations are divided into two divisions: Division 1 and Division 2, each with specific requirements.
Wiring Methods and Materials
- Permitted wiring methods in Class I, Division 1 include rigid metal conduit, flexible fittings, and approved boxes.
- MI cable must be terminated with approved fittings when used in Division 1 locations.
- Flexible connections at motor terminals are allowed if they use suitable fittings and cord connectors.
Conduit Seals and Installations
- Sealing compound is required for MI cable terminations to prevent moisture ingress.
- Conduit seals must be installed within specified distances of enclosures, particularly in Division 1 applications.
- Seals are necessary for conduit leaving Division 2 locations as well.
Equipment and Apparatus
- Equipment in Division 1 must be identified specifically for that location; the same applies to all utilization equipment regardless of voltage for signaling and communication systems.
- Circuit breakers must be installed within explosion-proof enclosures in Division 2 if not hermetically sealed or oil-immersed.
- Luminaires in Division 1 must indicate maximum wattage and be physically protected.
Flexible Cords and Cables
- Flexible cords are allowed in hazardous locations, provided they are listed for extra-hard usage and contain grounding conductors.
- The use of flexible cords in temporary setups must maintain continuous length from power sources to equipment.
- Shielding materials in twisted-pair cables don't need to be removed at conduit seals in both divisions if appropriately terminated.
Special Considerations
- Non-metallic conduits may be permitted under specific conditions in underground Division 1 locations.
- Conductors in sealing fittings should not exceed 25% of the cross-sectional area of the conduit.
- The use of FMC or LFMC in Division 2 requires equipment bonding as per existing codes.
Prohibitions and Exceptions
- General-purpose enclosures are generally permitted in Division 2 unless they contain make-and-break contacts as specified by regulations.
- Unions and couplings are prohibited between sealing fittings and boundaries of hazardous locations to maintain safety standards.
These notes provide a structured overview of the requirements and allowances within Class I hazardous (classified) locations as delineated in Article 501.
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Test your knowledge of Article 501 regarding electrical and electronic equipment in Class I hazardous locations. These flashcards cover key terminologies and safety requirements essential for understanding fire and explosion risks. Ideal for students and professionals working with hazardous electrical installations.
