Questions and Answers
Where in the NEC® would you find definitions related to hazardous locations?
The most severe hazardous classification is:
Which of the following groups represents the most hazardous location?
What is the classification and division of all floor-level areas up to a height of 18" in an airport hangar?
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A vented service pit in a commercial garage is a ____ location.
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Which of the following covers intrinsically safe equipment?
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A permanent and effective seal is one method of preventing the entrance of dust into enclosures through a raceway system in a Class II, Division 2 location. Another way is a _____.
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Which of the following best describes the devices that will help prevent moisture from collecting in raceway systems?
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A Class I, Division 1 location is best described as an atmosphere that ________ hazardous.
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The main purpose of seals or seal-offs in conduit runs is to _____.
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The main purpose of an explosion-proof flexible coupling is to connect ___.
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________ is approved for use in most Class I, Division 1 locations.
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All of the following are potential ignition sources except _____.
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In hazardous locations where threaded metal conduit is required, joints must be made up with at least ________ threads fully engaged.
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Anesthetizing locations of hospitals are considered to be _______ locations within 5' of the floor.
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The NEC lists ___ classification(s) of hazardous atmospheres.
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There is/are division(s) for each classification.
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There is/are group(s) listed under Class I, Division I.
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Which of the following are the groups listed under Class II, Division 1?
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When installing circuit breakers in Class II Division 1 hazardous locations, ____ must be used.
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When rigid metal conduit is required in hazardous locations, the threads must be cut at taper per foot:
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Study Notes
Hazardous Locations in Electrical Systems
- Definitions related to hazardous locations can be found in NEC Article 500.
- The most severe hazardous classification is Class 1, Division 1.
- Group A represents the most hazardous locations among classifications.
- All floor-level areas up to 18 inches in an airport hangar are classified as Class I, Division 2.
- A vented service pit in a commercial garage is categorized as Class 1, Division 2.
Intrinsically Safe Equipment and Safety Measures
- Intrinsically safe equipment is covered under NEC Article 504.
- To prevent dust from entering enclosures in Class II, Division 2 locations, use a horizontal raceway with a minimum length of 10 feet.
- Devices designed to prevent moisture collection in raceway systems include integral drains.
Classifications and Divisions
- Class I, Division 1 locations are characterized by an atmosphere that is normally hazardous.
- The purpose of seals or seal-offs in conduit runs is to prevent gases, vapors, or flames from transferring between system segments.
- An explosion-proof flexible coupling is primarily used to connect motors to a raceway system.
- Rigid metal conduit is generally approved for use in Class I, Division 1 locations.
Ignition Sources and Conduit Requirements
- Potential ignition sources include duplex receptacles, lighting fixtures, and circuit breakers; intrinsically safe equipment with make-or-break contacts is not a potential source.
- For threaded metal conduit in hazardous locations, a minimum of 5 threads must be fully engaged.
- Anesthetizing locations in hospitals, within 5 feet of the floor, are considered Class I, Division 1 locations.
Classifications of Hazardous Atmospheres
- The NEC recognizes three classifications of hazardous atmospheres.
- Each classification has two divisions.
- Four groups are listed under Class I, Division I: groups A, B, C, and D.
- Class II, Division 1 includes groups E, F, and G.
Installation and Safety Provisions
- Circuit breakers in Class II, Division 1 hazardous locations must be housed in a dust/ignition proof enclosure.
- When using rigid metal conduit in hazardous locations, ensure threads are cut to ¾" taper per foot.
- Unions in conduit runs aid in facilitating the installation and removal of equipment.
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Description
Test your knowledge on hazardous locations in electrical systems with this comprehensive quiz. Questions are based on the NEC (National Electrical Code) articles related to hazardous classifications and definitions. Perfect for electrical safety professionals and students alike.
