Unitary heat pump air conditioner having a compressed vapor diversion loop

A method for defrosting an external heat exchanger of a unitary heat pump air conditioner (HPAC) system, comprising the steps of:

• providing a refrigerant loop having:
• a condenser configured to condense a hot compressed refrigerant into a liquid refrigerant,
• an expansion device configured to receive and partially expand the liquid refrigerant from said condenser into a vapor-liquid phase refrigerant,
• an evaporator downstream of said expansion device configured to evaporate the vapor-liquid phase refrigerant into a cold vapor refrigerant, and
• a compressor configured to receive and compress the cold vapor refrigerant from said evaporator into the hot compressed refrigerant for said condenser;
• providing a cold coolant loop in thermal communication with said evaporator and said external heat exchanger;
• diverting at least a portion of said hot compressed refrigerant exiting from said compressor to said evaporator to transfer sufficient heat from said hot compressed refrigerant to said cold coolant loop to defrost said external heat exchanger.

A unitary heat pump air conditioner (Unitary HPAC), comprising:

• a refrigerant loop having a condenser for condensing a high pressure vapor,
• an evaporator downstream of said condenser for evaporating a low pressure liquid refrigerant, and
• a compressor for receiving a low pressure vapor refrigerant from said evaporator and discharging a high pressure vapor refrigerant to said condenser;
• a cold side heat exchanger configured to hydraulically connect to a cold side coolant loop, wherein said cold side heat exchanger is in thermal communication with said evaporator;
• a hot heat exchanger configured to hydraulically connect to a hot side coolant loop, wherein said hot heat exchanger is in thermal communication with said condenser;
• and
• a refrigerant diversion loop hydraulically connecting the hot compressed refrigerant exiting from said compressor to said evaporator.