HVAC system

A HVAC system comprising:

• a fluid circuit for conveying a refrigerant;
• a compressor for compressing the refrigerant;
• three heat exchangers defining an evaporator, an outdoor exchanger and a heat recovery exchanger provided along the fluid circuit;
• an expansion valve provided along the fluid circuit;
• and a receiver connected in parallel to the expansion valve, wherein a fill valve is located between the receiver and a connection upstream of the expansion valve and a drain valve is located between the receiver and a connection downstream of the expansion valve;
• wherein the fluid circuit comprises a plurality of valves which are configured to be controlled based on a selected operating mode such that at least one of the outdoor exchanger and the heat recovery exchanger is connected to a discharge line of the compressor and in series with one of the other heat exchangers which is connected to a suction line of the compressor, with the expansion valve disposed between:
• at least one of said outdoor exchanger and said heat recovery exchanger, and another one of said three heat exchangers, wherein the selected operating mode is selected from one or more operating modes including a partial heat recovery mode in which both the heat recovery exchanger and the outdoor exchanger are connected to the discharge line and the evaporator is connected to the suction line;
• wherein, in the partial heat recovery mode, a hot gas bypass valve upstream of the heat recovery exchanger diverts refrigerant to the outdoor exchanger in order to control the heat recovery at the heat recovery exchanger;
• wherein the fill valve and the drain valve are configured to be controlled to store a volume of refrigerant in the receiver so as to provide an effective refrigerant charge in the fluid circuit that corresponds to the selected operating mode.