CFC Commercial Refrigeration Systems 4 — Questions and Answers
Question 1: Under EPA Section 608, which of the following is NOT considered a violation when servicing commercial refrigeration equipment?
- Venting R-22 to atmosphere during repair
- Recovering refrigerant before opening the system (Correct answer)
- Knowingly releasing refrigerant while purging hoses
- Disposing of refrigerant containers with refrigerant remaining
Correct answer: Recovering refrigerant before opening the system
Recovering refrigerant before opening the system is the required and compliant practice under EPA Section 608.
Question 2: A commercial condensing unit is located on a rooftop and experiences high ambient temperatures in summer. Which control would help protect the compressor from overheating?
- Head pressure control valve
- High-pressure cutout switch (Correct answer)
- Crankcase pressure regulator
- Evaporator pressure regulator
Correct answer: High-pressure cutout switch
A high-pressure cutout switch shuts down the compressor when discharge pressure exceeds a safe limit caused by high ambient temperatures and poor heat rejection.
Question 3: In a commercial refrigeration system, subcooling of liquid refrigerant before the metering device primarily:
- Reduces compressor work
- Increases refrigerating effect and prevents flash gas (Correct answer)
- Raises suction pressure
- Reduces condenser size requirements
Correct answer: Increases refrigerating effect and prevents flash gas
Subcooling cools the liquid below its saturation temperature, increasing refrigerating effect and preventing flash gas formation at the metering device inlet.
Question 4: A commercial supermarket case is experiencing short cycling of the compressor. Which condition is most likely causing this?
- Oversized condenser
- Low-pressure cutout set too high or system low on charge (Correct answer)
- Excessive superheat
- Dirty condenser coil
Correct answer: Low-pressure cutout set too high or system low on charge
A low-pressure cutout set too high or insufficient refrigerant charge causes suction pressure to rapidly drop below the cutout setpoint, causing frequent short cycling.
Question 5: Which refrigerant was the first to be phased out under the Montreal Protocol due to its high ozone depletion potential (ODP)?
- R-134a
- R-410A
- R-11 (CFC-11) (Correct answer)
- R-407C
Correct answer: R-11 (CFC-11)
R-11 (CFC-11) has an ODP of 1.0 and was among the first refrigerants targeted for elimination under the Montreal Protocol's initial phase-out schedule.
Question 6: In a commercial refrigeration system, oil return to the compressor is most critical when the system uses:
- Flooded evaporators (Correct answer)
- Dry expansion evaporators
- Coaxial heat exchangers
- Plate heat exchangers
Correct answer: Flooded evaporators
Flooded evaporators maintain a pool of liquid refrigerant that can trap oil, making oil return design critical to prevent compressor oil starvation.
Question 7: What does a high suction pressure combined with low discharge pressure typically indicate in a commercial compressor?
- Refrigerant overcharge
- Restricted liquid line
- Worn or leaking compressor valves (Correct answer)
- Plugged filter drier
Correct answer: Worn or leaking compressor valves
Worn or leaking compressor valves reduce compression efficiency, allowing high-pressure gas to bleed back to the suction side, raising suction and lowering discharge pressure.
CFC Commercial Refrigeration Systems 4
Under EPA Section 608, which of the following is NOT considered a violation when servicing commercial refrigeration equipment?