The most cost-effective method of recovering refrigerant from a low pressure chiller with more than 500 lbs of refrigerant and to meet EPA requirements is to recover the refrigerant using what protocol?

Correct Answer: Option D — liquid recovery using a liquid pump, followed by vapor recovery using a vacuum pump based recovery unit

Extracting liquid first via a liquid pump minimizes recovery time for large low-pressure chillers containing over 500 lbs of refrigerant. Subsequent vacuum vapor recovery removes remaining refrigerant to meet EPA mandated evacuation levels efficiently.