Control devices & disconnects: Wisconsin Journeyman Electrician Practice Questions

A disconnect is required to be lockable in the open (off) position. What does the NEC require of the locking provision?

Section 110.25 requires the locking provision to remain in place with or without the lock installed; portable means that are removed with the lock do not qualify.

Three-way and four-way switches must be wired so that all switching is done in which conductor?

Section 404.2(A) requires three-way and four-way switches to switch only the ungrounded circuit conductor.

May a single-pole switch be installed to open only the grounded (neutral) conductor of a lighting circuit?

Section 404.2(B) does not allow switches or circuit breakers to disconnect the grounded conductor unless all circuit conductors open at the same time (or another listed exception applies).

Why does the NEC generally require a grounded (neutral) conductor at switch locations that control lighting loads?

Section 404.2(C) requires the grounded conductor at most lighting switch locations so electronic switches that need a neutral can be installed without using the equipment grounding conductor.

According to the NEC, may a wall switch be installed inside a shower space?

Section 404.4(C) prohibits switches within wet locations in tub or shower spaces unless installed as part of a listed tub or shower assembly.

A general-use switch or breaker is mounted so its handle operates vertically. Which handle position must mean on?

Section 404.7 requires the up position to be on when the handle operates vertically (double-throw switches excepted).

The center of the grip of a switch or breaker handle, in its highest position, may be no more than how far above the floor or working platform?

Section 404.8(A) limits the center of the operating handle grip to 2.0 m (6 ft 7 in) above the floor or working platform.

Snap switches are ganged in one box. When must they be separated by identified, securely installed barriers?

Section 404.8(B) requires barriers when the voltage between adjacent devices exceeds 300 V, such as 277-V switches on different phases of a 480Y/277-V system.

A general-use dimmer switch may control which loads, unless listed for others?

Section 404.14(E) limits general-use dimmers to controlling permanently installed incandescent luminaires unless listed for other loads.

An ac general-use snap switch controls a motor load. The motor load may be no more than what percentage of the switch ampere rating?

Section 404.14(A) allows ac general-use snap switches to control motor loads not exceeding 80% of the switch ampere rating at its rated voltage.

A motor controller is rated in horsepower. What must its horsepower rating be?

Section 430.83(A) requires controllers to have a horsepower rating at the application voltage not lower than the horsepower rating of the motor.

According to the NEC, how many controllers does each motor generally need?

Section 430.87 requires each motor to have its own individual controller, with limited exceptions for groups of motors under specific conditions.

According to the NEC, must a motor controller open all conductors to the motor?

Section 430.84 says a controller need not open all conductors to the motor unless it also serves as the disconnecting means.

How must a motor disconnecting means operate?

Section 430.103 requires the disconnect to open all ungrounded supply conductors simultaneously, with no pole operable independently.

A motor circuit has two disconnecting means. How many of them must be readily accessible?

Section 430.107 requires at least one of the disconnecting means to be readily accessible.