Defrost controls for heat pumps

Claim 1

AN AIR CONDITIONING SYSTEM COMPRISING A FIRST REFRIGERANT COMPRESSOR, A FIRST ELECTRIC MOTOR FOR DRIVING SAID COMPRESSOR, A FIRST INDOOR COIL, A FIRST OUTDOOR COIL, MEANS INCLUDING A FIRST REVERSAL VALVE CONNECTING SAID COMPRESSOR TO SAID COILS, A FIRST SOLENOID FOR ADJUSTING SAID VALVE TO OPERATE SAID OUTDOOR COIL AS AN EVAPORATOR COIL OR AS A CONDENSER COIL, A SECOND REFRIGERANT COMPRESSOR, A SECOND ELECTRIC MOTOR FOR DRIVING SAID SECOND COMPRESSOR, A SECOND INDOOR COIL, A SECOND OUTDOOR COIL, MEANS INCLUDING A SECOND REVERSAL VALVE CONNECTING SAID SECOND COMPRESSOR AND SAID SECOND COILS, A SECOND SOLENOID FOR ADJUSTING SAID SECOND VALVE TO OPERATE SAID SECOND OUTDOOR COIL AS AN EVAPORATOR COIL OR AS A CONDENSER COIL, A COMMON FAN FOR MOVING OUTDOOR AIR OVER SAID OUTDOOR COILS, A THIRD ELECTRIC MOTOR FOR DRIVING SAID FAN, A DEFROST CONTROL RESPONSIVE TO AIR PRESSURE DROP ACROSS SAID OUTDOOR COILS, SAID CONTROL HAVING A NORMALLY OPEN SWITCH WHICH CLOSES WHEN THERE IS A PREDETERMINED AIR PRESSURE DROP ACROSS SAID OUTDOOR COILS, A FIRST LIMIT CONTROL RESPONSIVE TO REFRIGERANT PRESSURE WITHIN SAID FIRST OUTDOOR COIL, SAID LIMIT CONTROL HAVING A NORMALLY OPEN SWITCH WHICH CLOSES WHEN THERE IS A PREDETERMINED PRESSURE WITHIN SAID FIRST OUTDOOR COIL, A SECOND LIMIT CONTROL RESPONSIVE TO REFRIGERANT PRESSURE WITHIN SAID SECOND OUTDOOR COIL, SAID SECOND LIMIT CONTROL HAVING A NORMALLY OPEN SWITCH WHICH CLOSES WHEN THERE IS A PREDETERMINED PRESSURE WITHIN SAID SECOND OUTDOOR COIL, A NORMALLY DEENERGIZED DEFROST RELAY HAVING A NORMALLY OPEN SWITCH AND A NORMALLY CLOSED SWITCH, ELECTRIC SUPPLY CONNECTIONS, MEANS INCLUDING SAID CLOSED SWITCH OF SAID DEFROST RELAY FOR CONNECTING SAID SOLENOIDS AND SAID THIRD MOTOR TO SAID CONNECTIONS, MEANS INCLUDING SAID SWITCH OF SAID DEFROST CONTROL FOR CONNECTING SAID RELAY TO SAID CONNECTIONS, MEANS INCLUDING A FIRST NORMALLY DEENERGIZED LOCKOUT RELAY HAVING A NORMALLY CLOSED SWITCH CONNECTING SAID FIRST MOTOR TO SAID CONNECTIONS, MEANS INCLUDING A SECOND NORMALLY DEENERGIZED LOCKOUT RELAY HAVING A NORMALLY CLOSED SWITCH CONNECTING SAID SECOND MOTOR TO SAID CONNECTIONS, MEANS INCLUDING SAID OPEN SWITCH OF SAID DEFROST RELAY AND SAID SWITCH OF SAID FIRST LIMIT CONTROL CONNECTING SAID FIRST LOCKOUT RELAY TO SAID CONNECTIONS, AND MEANS INCLUDING SAID OPEN SWITCH OF SAID DEFROST RELAY AND SAID SWITCH OF SAID SECOND LIMIT CONTROL CONNECTING SAID SECOND LOCKOUT RELAY TO SAID CONNECTIONS.