Elevator Mechanic Practice Exam

Relay STR has voltage, TRU has voltage, RU no voltage. Why?

1. Open at TRU 9/8

2. Closed at TRU 7/6

3. Short at RU 5/4

4. Fault at STR 3/2

The correct answer is: Open at TRU 9/8

The situation described indicates that the relay STR has voltage and TRU has voltage, while RU does not have voltage. This scenario suggests that there is a disruption in the path where RU should receive its voltage. When considering the option stating there is an open at TRU 9/8, this aligns with the expected outcome where this open could prevent the transfer of voltage to RU. The open circuit at this point means that energy can't reach RU, thus resulting in no voltage. In terms of the other potential reasons, if there were a closed condition at TRU 7/6, it typically would allow for voltage to pass through to RU. Similarly, if there were a short at RU 5/4, it would likely lead to undesired behaviors but not necessarily cause a complete loss of voltage at RU. Lastly, a fault at STR 3/2, while potentially affecting the circuit, wouldn’t directly explain the absence of power at RU given that STR itself has voltage. Thus, indicating that an open condition at TRU 9/8 effectively prevents RU from receiving any voltage provides clarity and insight into the reasoning behind the chosen answer.