CFESA Electrical and Mechanical Systems 2 — Questions and Answers
Question 1: What is the purpose of a contactor in commercial food equipment?
- To regulate voltage levels
- To switch high-current loads on and off via a low-current control circuit (Correct answer)
- To convert AC power to DC power
- To protect against ground faults
Correct answer: To switch high-current loads on and off via a low-current control circuit
A contactor uses a small control circuit to open and close contacts that switch heavy loads like compressors and heating elements.
Question 2: A commercial fryer's heating element reads infinite resistance with an ohmmeter. What does this indicate?
- The element is operating normally
- The element has an open circuit and must be replaced (Correct answer)
- The element has shorted to ground
- The element has low resistance due to overheating
Correct answer: The element has an open circuit and must be replaced
Infinite resistance on an ohmmeter indicates an open (broken) circuit within the heating element, meaning current cannot flow.
Question 3: Which type of mechanical seal failure would cause refrigerant oil to appear on the outside of a compressor?
- Valve plate failure
- Shaft seal leakage (Correct answer)
- Crankshaft bearing wear
- Piston ring blow-by
Correct answer: Shaft seal leakage
A leaking shaft seal allows refrigerant oil to migrate along the crankshaft and appear on the compressor exterior.
Question 4: When checking a three-phase motor for balance, what should the amperage readings between the three legs be?
- Exactly equal on all three legs
- Within 10% of each other (Correct answer)
- The center leg should read 50% higher
- Sequential increase from leg 1 to leg 3
Correct answer: Within 10% of each other
Amperage imbalance greater than 10% between legs indicates a problem with the power supply or the motor windings.
Question 5: What is the function of a pressure differential switch on a commercial ice machine?
- To regulate water flow to the ice-making grid
- To detect a dirty condenser or refrigerant restriction and shut the unit down (Correct answer)
- To cycle the harvest valve on and off
- To control the water pump speed
Correct answer: To detect a dirty condenser or refrigerant restriction and shut the unit down
A pressure differential switch monitors the difference between high and low side pressures and shuts down the machine if the spread indicates a problem like a dirty condenser.
Question 6: Which wiring method uses color-coded conductors where green or bare copper always indicates?
- The hot (live) conductor
- The neutral conductor
- The equipment grounding conductor (Correct answer)
- The switching leg conductor
Correct answer: The equipment grounding conductor
Per NEC standards, green insulation or bare copper conductor always identifies the equipment grounding conductor in a wiring system.
Question 7: A solenoid valve on a commercial steamer fails to open when energized. The coil has correct voltage applied. What should be checked next?
- The incoming water pressure only
- The coil resistance and the mechanical plunger for binding or corrosion (Correct answer)
- The thermostat calibration
- The main power fuse
Correct answer: The coil resistance and the mechanical plunger for binding or corrosion
If voltage is confirmed correct, a failed solenoid is either a burned coil or a mechanically stuck plunger, and both must be inspected.
CFESA Electrical and Mechanical Systems 2
What is the purpose of a contactor in commercial food equipment?