Abstract: A device for controlling or metering fluid flow in either direction through a conduit. The device comprises a shell disposed in communication with the conduit. Disposed within the shell is a body having a pair of metering orifices axially extending therethrough. A valve is, disposed within the shell and adapted such that fluid flow in a first direction through the device urges the valve to allow fluid flow through the first metering orifice and closes off the second metering orifice. Upon a flow reversal, the fluid urges the valves means to operate in the opposite manner wherein the first metering orifice is closed off and communication is established through the second metering orifice. The device is adapted for use in a reversible vapor compression air conditioning system. In this application, one metering orifice in the body is sized to provide proper metering for heating mode operation and one metering orifice is sized to provide proper metering for cooling mode operation.

Abstract: A defrost control for a heat pump system initiates a defrost when certain computed conditions are exceeded. The conditions include a limit as to the difference that may be permitted between the maximum temperature difference of two measured temperatures and the current difference of these measured temperatures. The two measured temperatures are the temperature of the indoor coil of the heat pump and the indoor air temperature of the air being heated by the indoor coil.