CFESA Repair Techniques 4 — Questions and Answers
Question 1: A commercial refrigeration system is short-cycling on the high-pressure cutout after a condenser coil cleaning. What is the most likely cause?
- Overcharge of refrigerant introduced during service (Correct answer)
- Worn compressor valves
- Low refrigerant charge
- Iced evaporator coil
Correct answer: Overcharge of refrigerant introduced during service
If refrigerant was added during service without first checking the charge, an overcharge can cause excessive high-side pressure and short-cycling on the high-pressure cutout.
Question 2: When repairing a commercial espresso machine, a technician finds the group head solenoid valve is not releasing pressure after extraction. What is the first repair step?
- Replace the boiler pressure stat
- Disassemble, clean, and inspect the solenoid valve plunger and seat for debris or wear (Correct answer)
- Adjust the pump pressure to minimum
- Replace the entire group head assembly
Correct answer: Disassemble, clean, and inspect the solenoid valve plunger and seat for debris or wear
The solenoid valve plunger or seat is most often blocked by scale or coffee oils, and cleaning resolves the issue before replacement is considered.
Question 3: A technician is repairing a commercial food slicer that vibrates excessively during operation. After confirming the blade is properly sharpened, what should be checked next?
- The index knob calibration
- The blade drive belt tension and condition, and motor mount integrity (Correct answer)
- The food carriage roller lubrication only
- The slice thickness gauge accuracy
Correct answer: The blade drive belt tension and condition, and motor mount integrity
A worn or improperly tensioned drive belt and loose motor mounts are common causes of excessive vibration in commercial slicers.
Question 4: Which method is used to properly set the superheat on a commercial refrigeration system after replacing the thermostatic expansion valve (TXV)?
- Set it by measuring suction line temperature and subtracting the saturated suction temperature at measured suction pressure (Correct answer)
- Set it to maximum adjustment and leave it
- Measure only the evaporator inlet pressure
- Set it by measuring liquid line temperature only
Correct answer: Set it by measuring suction line temperature and subtracting the saturated suction temperature at measured suction pressure
Superheat is calculated by subtracting the saturated suction temperature (from suction pressure) from the actual measured suction line temperature.
Question 5: A commercial ice machine is producing ice with a metallic taste. The water filtration was recently replaced. What is the most likely cause?
- Refrigerant leak into the water circuit
- New filter not flushed, leaving carbon fines in the water supply (Correct answer)
- Defrost cycle running too long
- Evaporator fan motor failure
Correct answer: New filter not flushed, leaving carbon fines in the water supply
New carbon block filters must be flushed to remove carbon fines before service; unflushed filters commonly cause off-tastes in ice.
Question 6: When repairing a commercial tilting skillet with a hydraulic tilt mechanism that moves too slowly, what is the appropriate corrective action?
- Replace the entire hydraulic cylinder
- Check hydraulic fluid level, condition, and adjust flow control valve if equipped (Correct answer)
- Increase electrical supply voltage
- Lubricate the tilting pivot pins only
Correct answer: Check hydraulic fluid level, condition, and adjust flow control valve if equipped
Low or degraded hydraulic fluid reduces system pressure and flow, causing slow movement; the flow control valve setting also affects tilt speed.
Question 7: A commercial reach-in freezer is running continuously but not reaching setpoint. Suction pressure is normal and the condenser is clean. What should the technician check next?
- The evaporator for ice blockage from a failed defrost system (Correct answer)
- The compressor motor winding resistance only
- The condenser fan blade pitch
- The door hinge spring tension
Correct answer: The evaporator for ice blockage from a failed defrost system
When suction pressure and condenser condition are normal but the unit cannot pull down, a blocked evaporator from failed defrost is the primary suspect.
CFESA Repair Techniques 4
A commercial refrigeration system is short-cycling on the high-pressure cutout after a condenser coil cleaning.
What is the most likely cause?