Patent ID: 7895850

Claim:
A method of operating a reversible heat pump system, comprising steps of: (a) sensing an outdoor air temperature with a first sensor; (b) sensing at least one condition of an outdoor heat exchanger coil with a second sensor; (c) electronically analyzing input received from said first sensor and said second sensor to predict when frosting on said outdoor heat exchanger coil may be imminent; and (d) modulating a proportioning reversing valve in response to said electronic analysis when the frosting on said outdoor heat exchanger coil may be imminent is predicted, said proportioning reversing valve directing a controlled proportional backpressure of pressurized refrigerant from a pressure side of a compressor into an outlet side of said outdoor heat exchanger coil while pressurized refrigerant is continued to be supplied to an indoor heat exchanger coil, whereby the pressure and temperature of refrigerant within said outdoor heat exchanger coil is raised to at least an extent necessary to prevent frosting on said outdoor heat exchanger coil without completely reversing the refrigeration cycle.