A refrigeration recovery machine specifies a maximum operating pressure of 2500 kPa (362 PSI). If a technician is recovering R-134a from a system with an ambient temperature of 30°C, and the system hoses introduce a pressure drop, what is the safest maximum pressure the recovery cylinder should reach to comply with the machine's limits?

Question: A refrigeration recovery machine specifies a maximum operating pressure of 2500 kPa (362 PSI). If a technician is recovering R-134a from a system with an ambient temperature of 30°C, and the system hoses introduce a pressure drop, what is the safest maximum pressure the recovery cylinder should reach to comply with the machine's limits?

Answer options: ✅ Approximately 1700 kPa (246 PSI), allowing for a safety margin and potential pressure increase in the tank during recovery.

• 2500 kPa (362 PSI), as this is the machine's stated maximum.
• Approximately 3000 kPa (435 PSI), to ensure maximum recovery efficiency before reaching the machine's cut-off.
• 1000 kPa (145 PSI), to prevent any risk of over-pressurization during recovery.

Correct answer: Approximately 1700 kPa (246 PSI), allowing for a safety margin and potential pressure increase in the tank during recovery.

Explanation: The saturation pressure of R-134a at 30°C is approximately 770 kPa. While the recovery machine has a high limit, the receiving cylinder's pressure will increase as it fills and warms. A significant safety margin is required to account for pressure rise due to absorption of heat (adiabatic compression), ambient temperature fluctuations, and ensuring the cylinder does not exceed its own working pressure limit, making 1700 kPa a more realistic and safer target for the cylinder pressure given typical recovery conditions.