Air conditioning system and defrosting operation method

Abstract

Temperature sensors detect an outdoor air temperature and a heat exchanger temperature of an outdoor unit, and a human detection sensor detects presence of a person in an air blowable region of each indoor unit. A control section selectively executes a first defrosting operation mode in which a defrosting operation is performed while fans of all the indoor units are stopped, and a second defrosting operation mode in which, when a frost formation amount in the heat exchanger is estimated to exceed a threshold value on the basis of the temperatures detected by the first and second temperature sensors, the indoor unit for which the human detection sensor detects no person in its air blowable region is preferentially selected, and a defrosting operation is performed while the fan of the indoor unit is forcibly operated. Such an air conditioning system and a defrosting operation method reduce time required for defrosting.

1 . An air conditioning system comprising:
 a plurality of indoor units;   an outdoor unit sharing a refrigerant system with the plurality of indoor units;   a first temperature sensor configured to detect an outdoor air temperature;   a second temperature sensor configured to detect a temperature of a heat exchanger of the outdoor unit;   a human detection sensor configured to detect whether or not there is a person in an air blowable region of each indoor unit; and   a control section configured to selectively execute a first defrosting operation mode and a second defrosting operation mode, the first defrosting operation mode being a mode in which a defrosting operation is performed while fans of all the indoor units are stopped, and the second defrosting operation mode being a mode in which, when it is estimated that a frost formation amount in the heat exchanger exceeds a threshold value on the basis of the respective temperatures detected by the first and second temperature sensors, the indoor unit for which the human detection sensor detects no person in the air blowable region thereof is preferentially selected, and a defrosting operation is performed while the fan of the indoor unit is forcibly operated.   
     
     
         2 . The air conditioning system according to  claim 1 , wherein the control section determines whether or not the forcible operation needs to be strengthened, on the basis of the temperature detected by the second temperature sensor after a certain time has elapsed since the execution of the second defrosting operation mode has been started, and only when the forcible operation needs to be strengthened, increases at least one of a revolution speed of the fan and the number of indoor units whose fans are operated. 
     
     
         3 . The air conditioning system according to  claim 1 , wherein the outdoor unit is provided with a setting switch for allowing use of the second defrosting operation mode. 
     
     
         4 . The air conditioning system according to  claim 1 , wherein
 in the case where at least two systems of a first system and a second system each including the indoor units, the outdoor unit, and the first and second temperature sensors are provided and the indoor units of the two systems are provided in a mixed manner in one room,   when executing the second defrosting operation mode in the first system, the control section operates the fans of the indoor units in the room with the second system set at a heating operation.   
     
     
         5 . A defrosting operation method performed in an air conditioning system including a plurality of indoor units and an outdoor unit sharing a refrigerant system with the plurality of indoor units, the defrosting operation method comprising:
 detecting an outdoor air temperature and a temperature of a heat exchanger of the outdoor unit by respective temperature sensors;   detecting whether or not there is a person in an air blowable region of each indoor unit by a human detection sensor; and   selectively executing, by a control section, a first defrosting operation mode and a second defrosting operation mode, the first defrosting operation mode being a mode in which a defrosting operation is performed while fans of all the indoor units are stopped, and the second defrosting operation mode being a mode in which, when it is estimated that a frost formation amount in the heat exchanger exceeds a threshold value on the basis of the respective temperatures detected by the first and second temperature sensors, the indoor unit for which the human detection sensor detects no person in the air blowable region thereof is preferentially selected, and a defrosting operation is performed while the fan of the indoor unit is forcibly operated.   
     
     
         6 . The air conditioning system according to  claim 2 , wherein the outdoor unit is provided with a setting switch for allowing use of the second defrosting operation mode.