Equipment & devices: Colorado Journeyman Wireman Practice Questions

According to the NEC, how must listed or labeled equipment be installed and used?

Section 110.3(B) ties the installation of listed or labeled equipment to the instructions that come with the listing or labeling.

A knockout was removed from a panelboard but no raceway or cable was installed in it. According to the NEC, what must be done with the opening?

Under 110.12(A), unused openings other than those for mounting or drainage must be closed so the protection is substantially equivalent to the wall of the equipment.

Which method of fastening electrical equipment to a concrete wall does the NEC prohibit?

Section 110.13(A) requires equipment to be firmly secured and does not allow wooden plugs driven into holes in masonry, concrete, plaster or similar materials.

Two conductors need to land under one terminal screw of a device. When does the NEC allow this?

Section 110.14(A) permits terminals for more than one conductor only where the terminal is identified for that use.

For a 30-A circuit whose equipment terminals are not marked otherwise, conductor ampacity is generally based on which temperature column?

For circuits rated 100 A or less, or conductors 14 AWG through 1 AWG, 110.14(C)(1)(a) limits termination temperature to 60°C unless the equipment is listed and marked for a higher rating.

For a 200-A feeder with conductors larger than 1 AWG, termination temperature for ampacity purposes is generally limited to:

Section 110.14(C)(1)(b) applies the 75°C limit to circuits over 100 A or conductors larger than 1 AWG, unless equipment is listed and marked otherwise.

The installation instructions give a numeric tightening torque for a panelboard's lugs. Which of these is an approved means to tighten them to that value?

Since the 2020 edition, 110.14(D) requires an approved means, such as a torque tool or a shear bolt, to reach the tightening torque marked on equipment or given in its instructions. Tightening by feel or with an impact driver is not an approved means.

Which field-applied hazard warning label meets the NEC?

Section 110.21(B) requires field-applied hazard markings to warn effectively, be permanently affixed, be durable for the environment and not be handwritten (except variable information).

According to the NEC, what must be legibly marked on each disconnecting means, unless it is obvious from its location and arrangement?

Section 110.22(A) requires each disconnecting means to be marked to show its purpose, with a marking durable enough for the environment.

In other than dwelling units, what must be field marked on service equipment?

Section 110.24(A) requires service equipment in other than dwelling units to be field marked with the maximum available fault current and the date of the calculation.

A 480-V switchboard has exposed live parts on both sides of the working space. What is the minimum working space depth?

Exposed live parts on both sides is Condition 3. For 151-600 V to ground, Table 110.26(A)(1) requires 4 ft (1.2 m).

A 208Y/120-V panelboard has exposed live parts on both sides of its working space (Condition 3). What is the minimum working space depth?

For 0-150 V to ground, Table 110.26(A)(1) requires 3 ft (900 mm) for all three conditions; 208Y/120 V is 120 V to ground.

A panelboard is 20 in wide. What is the minimum width of the working space in front of it?

Section 110.26(A)(2) requires the greater of 30 in (762 mm) or the width of the equipment, so a 20-in panel still needs 30 in.

A motor control center is 7 ft tall. What is the minimum height of the working space in front of it?

Section 110.26(A)(3) requires the greater of 6½ ft (2.0 m) or the height of the equipment, so 7-ft equipment needs 7 ft.

According to the NEC, may the required working space in front of a panelboard be used to store boxes of material?

Section 110.26(B) prohibits using required working space for storage.