Electrical Systems and Controls Flashcards

An inspector notes that the main power disconnect for a traction elevator is located in an electrical closet adjacent to the machine room. The disconnect is not visible from the location of the elevator controller. According to NEC 620.51, why is this a violation?

Answer: The disconnect must be located within sight of the motor controller.

NEC 620.51(C) requires the disconnecting means to be located within sight of the motor controller. This is a critical safety requirement to ensure that a technician working on the controller can visually confirm that the power source has been de-energized.

According to the National Electrical Code (NEC), 125-volt, single-phase, 15- and 20-ampere receptacles in which of the following elevator spaces must have ground-fault circuit-interrupter (GFCI) protection for personnel?

Answer: In the elevator pit and machine room.

NEC 620.85 explicitly requires GFCI protection for 125V, 15- and 20-ampere receptacles installed in elevator pits, machine rooms, machinery spaces, and on car tops, due to the increased risk of electrical shock in these potentially damp or grounded environments.

What is the immediate and primary electrical function that occurs when any contact in the elevator's main safety circuit string (e.g., a hoistway door interlock, governor contact, or stop switch) is opened?

Answer: Power is removed from the drive motor and the brake coil, causing the brake to set.

The safety circuit is a series circuit of contacts that, when intact, allows power to be supplied to the motor and brake. If any contact in this series is opened, it immediately breaks the circuit that energizes the drive motor and the brake coil. This de-energizes the brake, causing it to set by spring force, and removes power from the motor, bringing the elevator to a stop.

Which of the following is a recognized method for initiating Phase I Firefighters' Emergency Operation, causing the elevator to return to a designated recall level?

Answer: Activating a smoke detector in an elevator lobby or machine room.

ASME A17.1 specifies that Phase I Firefighters' Emergency Operation can be initiated in two ways: manually with a key switch in the lobby, or automatically by the activation of specific fire alarm initiating devices, such as smoke detectors located in elevator lobbies, the machine room, or the hoistway.

While inspecting the installation of traveling cables in a new traction elevator, a QEI observes that the cables hang freely from the car to the hoistway junction box with no intermediate support. Why is this a potential violation?

Answer: The installation lacks a means to prevent strain on the terminations and control twisting.

Both NEC Article 620 and ASME A17.1 require that traveling cables be suspended and supported to prevent placing mechanical strain on the electrical terminations and to prevent damage from twisting or rubbing. This is typically accomplished with a suspension device or hanger.

When more than one elevator's driving machine is supplied by a single feeder circuit, what is the primary requirement for the overcurrent protective devices in each elevator's disconnecting means, according to NEC 620.62?

Answer: They must be selectively coordinated with the supply-side overcurrent device.

NEC 620.62 requires selective coordination when multiple elevators are on a single feeder. This ensures that a fault condition in one elevator will only trip the protective device for that specific elevator, rather than tripping the main feeder breaker and shutting down all elevators on that circuit.