Compressor floodback is a common cause of HVAC/R system failure. Floodback occurs when uncontrolled liquid refrigerant enters the compressor during system operation. In an HVAC/R system, the refrigerant exits the evaporator and enters the compressor in a vapor state. But when the refrigerant is not vaporized entirely in the evaporator, a part of it gets sucked into the compressor in its liquid form. Compressor floodback may be misdiagnosed as compressor failure, even though the compressor doesn’t cause this phenomenon.