Patent ID: 7908881

Claim:
An HVAC system comprising: a main circuit comprising a main circuit evaporator, a main circuit expansion device, a main circuit condenser and a main circuit compressor connected in a first closed refrigerant loop; a subcooler circuit comprising a subcooler evaporator, a subcooler expansion device, a subcooler condenser and a subcooler compressor connected in a second closed refrigerant loop, wherein the subcooler compressor is configured to compress high-pressure refrigerant and the subcooler circuit utilizes a refrigerant with a lower operating pressure than the refrigerant in the main circuit, wherein the subcooler circuit is selectably operable; the subcooler evaporator being arranged and disposed to exchange heat between liquid refrigerant in the main circuit and the refrigerant in the subcooler circuit to cool the liquid refrigerant in the main circuit prior to entering the main circuit evaporator, wherein the main circuit condenser operates independently of the subcooler circuit; wherein the coils of the subcooler circuit condenser are positioned downstream of a cooling fluid passing over coils of the main circuit condenser; wherein a fluid moving device moves the cooling fluid through the subcooler condenser and the main circuit condenser; wherein a cooling capacity of the subcooler circuit is less than a cooling capacity of the main circuit; and wherein the operation of the subcooler circuit provides an increased cooling capacity per unit of a mass flow of cooling fluid through the main circuit condenser and subcooler condenser for the HVAC system with a predetermined design efficiency.