309A Wiring Methods and Materials 4 — Questions and Answers
Question 1: What is the maximum distance between supports for 1/2-inch rigid metal conduit?
- 1.5 m
- 2.0 m
- 2.5 m
- 3.0 m (Correct answer)
Correct answer: 3.0 m
CEC Table 12-22 specifies a maximum support spacing of 3.0 m for rigid metal conduit of 1/2-inch to 1-inch trade size, as the rigidity of the conduit allows wider spacing than EMT.
Question 2: What conductor type is typically used for service entrance cables in Canadian residential installations?
- NMD90
- TECK90
- RW90 XLPE (Correct answer)
- AC90
Correct answer: RW90 XLPE
RW90 XLPE (cross-linked polyethylene) conductors are commonly used for service entrance wiring because they are rated for wet locations, have excellent dielectric properties, and meet CEC requirements.
Question 3: According to the CEC, what is the maximum number of quarter bends (90°) allowed in a conduit run between pull points?
- 2
- 3
- 4 (Correct answer)
- 5
Correct answer: 4
The CEC limits conduit runs to four quarter bends (totalling 360°) between pull points. This prevents excessive friction that would make conductor pulling difficult or damage insulation.
Question 4: What is the primary purpose of using a seal-off fitting at a conduit entrance to an enclosure?
- To provide strain relief
- To prevent the passage of gases, vapours, or moisture (Correct answer)
- To act as a grounding point
- To prevent electromagnetic interference
Correct answer: To prevent the passage of gases, vapours, or moisture
Seal-off fittings are filled with sealing compound to prevent gases, vapours, flames, or moisture from passing through the conduit system, particularly important at boundaries of hazardous areas.
Question 5: What cable type must be used for wiring fire alarm circuits in Canada?
- NMD90 with red jacket
- Standard TECK90
- FAS-rated cable (fire alarm system cable) (Correct answer)
- Any conductor in red conduit
Correct answer: FAS-rated cable (fire alarm system cable)
CEC Section 32 and fire alarm standards require FAS-rated (Fire Alarm System) cable for fire alarm circuits. This cable is specifically designed to maintain circuit integrity during fire conditions.
Question 6: What is the purpose of the green-coloured conductor or green stripe in a cable assembly?
- It identifies the neutral conductor
- It identifies the bonding/grounding conductor (Correct answer)
- It identifies the high-leg conductor
- It is used for switch legs only
Correct answer: It identifies the bonding/grounding conductor
The CEC designates green or green with a yellow stripe for the bonding (grounding) conductor. This conductor connects equipment to the grounding system for fault protection.
309A Wiring Methods and Materials 4
What is the maximum distance between supports for 1/2-inch rigid metal conduit?