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

EPA regulations for large low-pressure chillers mandate maximizing recovery efficiency. Extracting liquid refrigerant first via a liquid pump removes the bulk of the mass rapidly, followed by using a vacuum-based vapor recovery unit to pull remaining refrigerant down to required vacuum levels.