A heat pump system includes a compressor, indoor and outdoor coils and {HEAD ~ a four way valve} for automatically reversing {TAIL ~ refrigerant} to provide cooling or heating mode of operation 
A heat pump system includes a compressor , indoor and outdoor coils and { HEAD ~ a four way valve } for automatically reversing { TAIL ~ refrigerant } to provide cooling or heating mode of operation
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH