CFESA Diagnostic Troubleshooting 5 — Questions and Answers
Question 1: A commercial ice machine produces hollow or incomplete cubes. Refrigerant charge and water supply are confirmed normal. What is the most likely cause?
- Failed bin thermostat
- Low water distributor flow or clogged water nozzles (Correct answer)
- Faulty harvest solenoid
- Excessive ambient temperature
Correct answer: Low water distributor flow or clogged water nozzles
Clogged water nozzles in the distributor reduce water coverage over the evaporator plate, resulting in hollow or incomplete ice cube formation.
Question 2: A technician finds a commercial refrigerator compressor running continuously with the box temperature above setpoint. Suction pressure is low and superheat is high. What does this indicate?
- Overcharge of refrigerant
- Undercharge of refrigerant or refrigerant leak (Correct answer)
- Faulty condenser fan
- Stuck-open expansion valve
Correct answer: Undercharge of refrigerant or refrigerant leak
Low suction pressure combined with high superheat is a classic indicator of insufficient refrigerant in the system, pointing to a leak or undercharge.
Question 3: A combi oven displays an error code indicating a steam generation fault. The technician confirms water supply is present. What should be inspected next?
- Door latch mechanism
- Steam generator scale buildup or heating element failure (Correct answer)
- Combustion air fan
- Grease drain trap
Correct answer: Steam generator scale buildup or heating element failure
Scale buildup on the steam generator heating element or a burned-out element are the most common causes of steam generation faults when water supply is adequate.
Question 4: A gas range burner produces a yellow, lifting flame instead of a blue cone flame. What is the most likely cause?
- Excess primary air at the air shutter
- Insufficient primary air or partially blocked air shutter (Correct answer)
- High gas supply pressure
- Cracked burner cap
Correct answer: Insufficient primary air or partially blocked air shutter
A yellow, lifting flame indicates incomplete combustion due to insufficient primary air mixing with the gas before ignition.
Question 5: After replacing a thermostat on a commercial fryer, the oil continues to overheat past the setpoint. What is the most likely oversight?
- The fryer needs a full oil change
- The new thermostat bulb is not fully seated in its well (Correct answer)
- The high-limit switch needs calibration
- The gas valve orifice is the wrong size
Correct answer: The new thermostat bulb is not fully seated in its well
If the thermostat sensing bulb is not fully inserted into the capillary well, it senses a lower temperature than actual oil temperature, causing uncontrolled overheating.
Question 6: A commercial refrigerator compressor hums but does not start. The technician confirms proper voltage at the compressor terminals. What should be tested first?
- Condenser coil cleanliness
- Start relay and start capacitor (Correct answer)
- Evaporator fan motor
- Refrigerant charge level
Correct answer: Start relay and start capacitor
A humming compressor that fails to start typically indicates a faulty start relay or start capacitor that is not providing the necessary torque to initiate rotation.
Question 7: A technician is diagnosing a commercial steamer that produces steam but the cooking cavity temperature is below specification. What should be checked?
- Water hardness levels
- Steam generator output pressure and door seal integrity (Correct answer)
- Drain line flow rate
- Control board firmware version
Correct answer: Steam generator output pressure and door seal integrity
Inadequate steam generator pressure output or a leaking door seal allows steam to escape, reducing cavity temperature below the required cooking specification.
CFESA Diagnostic Troubleshooting 5
A commercial ice machine produces hollow or incomplete cubes.
Refrigerant charge and water supply are confirmed normal.
What is the most likely cause?