Patent ID: 8549867

Claim:
A heat pump system, comprising: a closed system including: a condensing heat exchanger coil; an evaporating heat exchanger coil; a refrigerant; and a compressor configured to compress said refrigerant, thereby causing said refrigerant to have a greater pressure in said condensing heat exchanger coil than in said evaporating heat exchanger coil; a flow valve having a plurality of ports and a reversing slide valve for directing the refrigerant with respect to the compressor; and a controller configured to perform a passive defrost of said evaporating heat exchanger coil that includes disabling said compressor and providing a low-resistance bypass path between said condensing and evaporating heat exchanger coils that bypasses said compressor, wherein the slide valve floats off of a valve seat within the flow valve thereby allowing said refrigerant to flow from said condensing heat exchanger coil to said evaporating heat exchanger coil while said compressor is disabled.