designed with the functional units a and b 141 142 separated the separate cooling and heating operates without any restrictions compared with system of fig3 the combined operation is different in that depending on the direction of the refrigerant flow in the circuit there is more cooling or more heating in the combined operation with higher heating output with dehumidification the refrigerant passes the functional unit b 142 and is then restricted in the expansion valve passable in both directions 192 therefore in the second functional unit a 141 there is a restricted refrigerant for dehumidification if there is too little additional heating the corresponding cooling power is also small the air flow in the ventilation system 103 is equal with that seen in fig3 in the combined operation with higher cooling output and dehumidification the refrigerant is released between the two functional units a and b 141 142 of the internal heat exchanger system in the expansion valve 192 which is passable in both directions as the refrigerant has already been cooled in the external heat exchanger 107 and inner heat exchanger 108 there is only a low heating capacity available in the functional unit a 141 but a high cooling capacity in the functional unit b 142 therefore this mode is called the mode with increased cooling capacity cooling of the refrigerant can be influenced by the speed of the engine fan the airflow 116 in the ventilation system 103 must be reversed in this mode.