A technician is using a system-dependent (passive) recovery device to recover R-22 from a small high-pressure appliance. Which of the following conditions is MOST likely to cause the recovery process to be extremely slow or stop prematurely?
- AThe recovery cylinder is placed in an ice bath.
- BThe recovery cylinder pressure is lower than the appliance pressure.
- CThe system's compressor is operating during recovery.
- DThe ambient temperature is significantly colder than the appliance.
Show answer & explanationAnswer & explanation
Correct answer: D. The ambient temperature is significantly colder than the appliance.
System-dependent recovery relies on the pressure differential between the appliance and the recovery cylinder. If the ambient temperature is significantly colder than the appliance, the pressure in the appliance will be lower, reducing the pressure differential and slowing or stopping the transfer of refrigerant to the recovery cylinder. Placing the recovery cylinder in an ice bath (option A) would actually speed up recovery by lowering the cylinder's pressure, and operating the compressor (option B) would increase appliance pressure, also speeding it up. Option D describes the ideal condition for recovery.
Why the other options are wrong
- A. An ice bath for the recovery cylinder would lower its pressure, increasing the pressure differential and speeding up recovery.
- B. This is the desired condition for efficient recovery, not a cause for slowness.
- C. An operating compressor would increase the pressure in the appliance, speeding up recovery.
System-Dependent Recovery Speed
The speed of system-dependent (passive) recovery is primarily determined by the pressure differential between the appliance and the recovery cylinder.
- Higher appliance pressure relative to cylinder pressure speeds up recovery.
- Lower ambient temperature reduces appliance pressure, slowing recovery.
- Heating the appliance or cooling the cylinder can improve recovery speed.
Memory trick: Pressure difference is the key; if it's low, recovery is slow, you see!