Abstract: An HVAC system for heating and cooling a passenger compartment of a vehicle includes a first heat exchanger that transfers heat between a primary loop and a secondary loop. The primary loop is a reversible loop and uses high pressure refrigerant. A compressor pressurizes the refrigerant. A second heat exchanger selectively transfers heat energy to and from the passenger compartment. The secondary loop is a low pressure liquid coolant loop that passes through the first heat exchanger. A pump moves fluid through the secondary loop. A third heat exchanger transfers heat to and from an external medium from the fluid passing through the secondary loop. A secondary heat source adds heat to the secondary loop during a heating mode. A bypass means selectively bypasses the secondary heat source during a cooling mode.

Abstract: An HVAC system for heating and cooling a passenger compartment of a vehicle is provided. A first heat exchanger transfers heat between a primary loop and a secondary loop. The primary loop is a reversible loop and uses high pressure refrigerant. A compressor pressurizes the refrigerant. A second heat exchanger selectively transfers heat energy to and from the passenger compartment. The secondary loop is a low pressure liquid coolant loop that passes through the first heat exchanger. A pump moves fluid through the secondary loop. A third heat exchanger transfers heat to and from an external medium from the fluid passing through the secondary loop. A secondary heat source adds heat to the secondary loop during a heating mode. A bypass means selectively bypasses the secondary heat source during a cooling mode.