CME Special Occupancies and Equipment 2 — Questions and Answers
Question 1: In a Class II, Division 1 location involving combustible dust, what type of enclosure is required for electrical equipment?
- Weatherproof
- Dust-ignitionproof (Correct answer)
- Explosionproof
- Rainproof
Correct answer: Dust-ignitionproof
Class II locations involve combustible dust hazards, requiring dust-ignitionproof enclosures that prevent dust entry and any internal arcing from igniting surrounding dust.
Question 2: Under NEC Article 517, the critical branch of a hospital's essential electrical system must restore power within how many seconds of interruption?
- 5 seconds
- 10 seconds (Correct answer)
- 30 seconds
- 60 seconds
Correct answer: 10 seconds
NEC 517.31(B) requires the critical branch to be restored within 10 seconds, as it serves life-safety loads such as critical care areas and task illumination.
Question 3: Class III hazardous locations are characterized by the presence of:
- Flammable gases or vapors
- Combustible dust
- Ignitable fibers or flyings (Correct answer)
- Explosive chemical compounds
Correct answer: Ignitable fibers or flyings
Class III locations are those where ignitable fibers or flyings are present but not likely to be in suspension in sufficient quantities to produce ignitable mixtures.
Question 4: Under the NEC Article 505 Zone system, equipment used in a Zone 0 location must be classified as:
- Category 1 (Correct answer)
- Category 2
- Category 3
- Zone-rated only
Correct answer: Category 1
Zone 0, where explosive atmospheres are continuously present, requires Category 1 equipment providing the highest protection level for continuous ignition risk.
Question 5: NEC 517.20 requires what protection for receptacles and fixed equipment in wet procedure locations of healthcare facilities?
- AFCI protection only
- Isolated power system or GFCI protection (Correct answer)
- Double-insulated equipment exclusively
- Explosionproof outlets
Correct answer: Isolated power system or GFCI protection
NEC 517.20 requires wet procedure locations to use either an isolated power system or GFCI protection to safeguard patients from electric shock.
Question 6: In a Class I, Division 2 location, general-purpose enclosures are acceptable for which type of equipment?
- Switches that interrupt current under load
- Motors that do not have arc-producing devices (Correct answer)
- All electrical equipment without restriction
- Fuses rated over 600 volts
Correct answer: Motors that do not have arc-producing devices
NEC 501.125(B) permits motors without arc-producing brushes or switching mechanisms to use general-purpose enclosures in Class I Division 2 locations.
Question 7: Per NEC 501.15, the sealing compound used to fill conduit seals in Class I hazardous locations must be:
- Portland cement mixed with sand
- A compound listed for the purpose (Correct answer)
- Any UL-listed caulk
- Epoxy resin rated for 600V
Correct answer: A compound listed for the purpose
NEC 501.15 requires conduit seals to be filled with a sealing compound specifically listed for use in hazardous location seals to prevent gas or vapor passage.
CME Special Occupancies and Equipment 2
In a Class II, Division 1 location involving combustible dust, what type of enclosure is required for electrical equipment?