Intrinsically safe circuits, per Article 100 of the NEC, are those incapable of producing an arc with enough energy to ignite a flammable or combustible material in the air under test conditions. Although Section 504.7 indicates that any wiring method could be installed, a variety of requirements apply to these circuits and systems.
Created by: Michael Johnston
1. Articles 500–504 require equipment construction and installation that ensure safe performance under conditions of proper use and maintenance. Suitability of identified equipment for hazardous (classified) locations shall be determined by which of the following:
A. Equipment listing or labeling
B. Evidence of equipment evaluation from a qualified testing laboratory or inspection agency concerned with product evaluation
C. Evidence acceptable to the authority having jurisdiction, such as a manufacturer’s self-evaluation or an owner’s engineering judgment
D. Any one of the above
2. All intrinsically safe and associated apparatuses—other than simple apparatuses described on the control drawing—are not required
to be listed.
3. Intrinsically safe circuit wiring shall be permitted to be installed in ______ where located in a Class I, Division 1 location(s).
A. Rigid metal conduit
B. Intermediate metal conduit
C. Rigid PVC conduit
D. Any of the above
4. Bonding of noncurrent-carrying equipment parts, raceways and other enclosures in hazardous (classified) locations as defined in sections 500.5, 505.5 and 506.5 shall be ensured by any of the bonding means provided in Section 250.92(B)(2) through (B)(4) at which of the following voltages?
A. 9V DC
B. 12V AC
C. 24V AC
D. All of the above
5. Which color code must be used to identify intrinsically safe conductors?
B. Light blue
6. Raceways, other than underground raceways, containing intrinsically safe system wiring shall be identified with the wording “Intrinsic Safety Wiring” or equivalent so that the raceway can be traced through the entire length of the installation. Spacing between labels shall not exceed ______ feet.
7. A method of separating intrinsically safe circuit conductors from those that are not intrinsically safe within
an enclosure is by a space separation of not less than ______.
A. ¼ inch
B. ½ inch
C. 1 inch
D. 2 inches
8. Conduits containing intrinsically safe circuit wiring are required to be sealed to minimize the passage of gases or vapors, and the sealing fitting is required to be explosion-proof.
9. Associated apparatuses and cable shields of intrinsically safe circuits are required to be grounded in accordance with which of the following?
A. The required control drawing
B. Section 250.8
C. Section 250.118
D. Section 250.130
10. ______ locations are those in which flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors are, or may be, present in the air in quantities sufficient to produce explosive or ignitable mixtures.
A. Class I
B. Class II
C. Class III
D. Middle Class