WALMART MAINTENANCE Electrical Systems 4 — Questions and Answers
Question 1: A fluorescent light fixture flickers intermittently. What is the MOST likely cause?
- Faulty ballast or lamp (Correct answer)
- Overloaded circuit breaker
- Incorrect wire gauge
- Grounding fault in the panel
Correct answer: Faulty ballast or lamp
Intermittent flickering in fluorescent fixtures is most commonly caused by a failing ballast or end-of-life lamp.
Question 2: What does a power factor of 0.85 mean for an electrical load in a retail facility?
- 85% of apparent power is converted to useful work (Correct answer)
- 15% of power is lost as heat in conductors
- The voltage leads the current by 85%
- The circuit uses 85 watts per amp
Correct answer: 85% of apparent power is converted to useful work
A power factor of 0.85 means 85% of the apparent power (kVA) is converted into real, useful work (kW).
Question 3: Which type of motor is most commonly used for HVAC compressors in large Walmart stores?
- DC shunt motor
- Single-phase capacitor-start motor
- 3-phase induction motor (Correct answer)
- Universal series motor
Correct answer: 3-phase induction motor
3-phase induction motors are standard for HVAC compressors in commercial facilities due to their efficiency and reliability.
Question 4: What is the maximum voltage drop allowed by NEC recommendations for branch circuits in commercial buildings?
- 1%
- 3% (Correct answer)
- 5%
- 10%
Correct answer: 3%
The NEC recommends a maximum 3% voltage drop on branch circuits to ensure proper equipment operation.
Question 5: When replacing a circuit breaker, what must be verified FIRST after installation?
- The breaker amperage rating matches the circuit load
- The breaker is the correct amperage for the wire gauge
- The breaker manufacturer matches the panel brand
- All of the above must be verified (Correct answer)
Correct answer: All of the above must be verified
All three factors must be verified: wire gauge rating, load requirements, and panel compatibility are all critical for safe installation.
Question 6: A photoelectric sensor on an automatic door fails to trigger. The FIRST diagnostic step should be:
- Replace the sensor immediately
- Check the power supply voltage to the sensor (Correct answer)
- Adjust the door closing speed
- Inspect the door frame for physical damage
Correct answer: Check the power supply voltage to the sensor
Verifying the power supply voltage is the first step, as no power is the most common and easiest-to-diagnose cause of sensor failure.
Question 7: What wire gauge is typically used for a 20-amp, 120V branch circuit in a commercial facility?
- 14 AWG
- 12 AWG (Correct answer)
- 10 AWG
- 8 AWG
Correct answer: 12 AWG
12 AWG copper wire is rated for 20 amps and is the standard for 20-amp branch circuits per the NEC.
WALMART MAINTENANCE Electrical Systems 4
A fluorescent light fixture flickers intermittently.
What is the MOST likely cause?