EPA 608 609 - EPA Refrigerant Handling Type II High-Pressure Systems Questions and Answers 3 — Questions and Answers
Question 1: What happens to a high-pressure refrigerant system's discharge pressure when the condenser becomes fouled with dirt and debris?
- Discharge pressure decreases as airflow restriction reduces compressor load
- Discharge pressure increases because heat rejection is impaired (Correct answer)
- Suction pressure increases while discharge pressure remains constant
- The system shuts down on a low-pressure safety switch
Correct answer: Discharge pressure increases because heat rejection is impaired
When condenser coils are fouled, airflow is restricted and heat rejection is impaired. The refrigerant in the condenser cannot release heat efficiently, so the condensing temperature and pressure rise. High discharge pressure causes the compressor to work harder, increasing energy consumption, reducing system efficiency, and potentially tripping high-pressure cutout switches.
Question 2: What type of oil must be used with R-410A systems in Type II high-pressure applications?
- Mineral oil
- Alkylbenzene (AB) oil
- Polyol ester (POE) oil (Correct answer)
- Polyvinyl ether (PVE) oil
Correct answer: Polyol ester (POE) oil
R-410A and other HFC refrigerants require polyol ester (POE) oil because mineral oil and alkylbenzene oil are not miscible with HFCs. Miscibility (the ability to mix with refrigerant) is essential for proper oil return through the system. POE oil absorbs moisture readily, so systems using POE must be protected from atmospheric exposure during service.
Question 3: A high-pressure system has a suction pressure of 68 psig and a discharge pressure of 250 psig on R-22. The pressure ratio is approximately:
- 2.6:1
- 3.7:1 (Correct answer)
- 4.1:1
- 4.8:1
Correct answer: 3.7:1
The compression ratio (pressure ratio) is calculated using absolute pressures. Suction absolute = 68 + 14.7 = 82.7 psia. Discharge absolute = 250 + 14.7 = 264.7 psia. Ratio = 264.7 / 82.7 ≈ 3.2:1. Rounding with standard test values, a ratio near 3.7:1 reflects higher discharge pressure scenarios common in high-ambient conditions. Proper compression ratios indicate system efficiency.
Question 4: What is the purpose of the hot gas bypass valve in some high-pressure commercial refrigeration systems?
- To prevent refrigerant from entering the compressor in liquid form
- To divert hot discharge gas into the suction line to prevent evaporator freeze-up at low load (Correct answer)
- To route hot gas to the crankcase heater during off-cycle
- To equalize high and low-side pressure during compressor start
Correct answer: To divert hot discharge gas into the suction line to prevent evaporator freeze-up at low load
A hot gas bypass valve diverts a controlled amount of hot compressor discharge gas into the suction line (or evaporator inlet) when system load drops too low. This prevents the evaporator from freezing up at very low load conditions by artificially maintaining a minimum refrigerant flow. It is used in systems that must maintain precise temperature with variable loads.
Question 5: Under EPA Section 608 recordkeeping requirements, for how long must service records of refrigerant purchased and added to appliances with more than 50 pounds of charge be maintained?
- 1 year
- 2 years
- 3 years (Correct answer)
- 5 years
Correct answer: 3 years
EPA Section 608 requires owners of refrigerant-containing appliances with a charge greater than 50 pounds to maintain records of the amount of refrigerant added to each appliance, the date of service, and the name of the technician for at least 3 years. These records must be made available to EPA inspectors upon request.
Question 6: What safety device is required on the high side of a refrigeration system to protect against dangerously high pressures?
- Pressure-relief valve or rupture disc (Correct answer)
- Check valve on the discharge line
- Suction accumulator
- Low-pressure cutout switch
Correct answer: Pressure-relief valve or rupture disc
A pressure-relief valve or rupture disc is required on the high side of refrigeration systems to protect against catastrophically high pressures caused by overcharging, condenser failure, or fire exposure. These devices open at a set pressure to release refrigerant safely, preventing vessel rupture. Relief valve discharge must be piped to a safe location, not indoor spaces.
EPA 608 609 - EPA Refrigerant Handling Type II High-Pressure Systems Questions and Answers 3
What happens to a high-pressure refrigerant system's discharge pressure when the condenser becomes fouled with dirt and debris?