NEIEP Mechanics Practice Exam

If an elevator is responding to a call from the 3rd floor, when will the U relay stop being energized?

1. When the car reaches the 3rd floor

2. When the selector switch #3 opens

3. When the call is canceled

4. When the elevator door opens

The correct answer is: When the selector switch #3 opens

The U relay in an elevator system is designed to be energized in response to calls for the elevator. It typically remains energized until certain conditions are met, indicating that the elevator has responded to the call. The correct answer focuses on the role of the selector switch, which is crucial for the operation of the elevator control system. When the elevator is called to a specific floor, such as the 3rd floor, the selector switch for that floor closes to signal the system to dispatch the elevator. Once the elevator reaches the designated floor, the selector switch for the 3rd floor opens. This action de-energizes the U relay, effectively signifying that the requested service has been completed and the elevator can now perform other functions or respond to new calls. While the other options may seem relevant, they do not directly address the mechanism that specifically governs the energization of the U relay. For instance, while the elevator door opening might indicate that the elevator has arrived, it alone does not trigger the de-energization of the U relay. The same goes for when the elevator reaches the 3rd floor; the U relay remains energized until the corresponding selector switch opens. Additionally, the cancellation of the call could affect how the elevator operates, but it