The first four way valve is used to direct refrigerant periodically to flow in a series through each coil when {HEAD ~ that coil} is operating as {TAIL ~ a condenser} and to receive refrigerant flowing in parallel circuit when a coil is operating as an evaporator 
The first four way valve is used to direct refrigerant periodically to flow in a series through each coil when { HEAD ~ that coil } is operating as { TAIL ~ a condenser } and to receive refrigerant flowing in parallel circuit when a coil is operating as an evaporator
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH