Abstract: An improved method and apparatus for limiting the pressure in the high pressure side of a heat pump system to a safe value, without causing the defrost control circuitry thereof to initiate unnecessary defrost cycles. When the heat pump system is operating in its heating mode, pressure limiting circuitry limits the pressure in the high side thereof to a safe value by turning the outdoor fan off, and holding it off, when the vapor pressure in the vapor containing parts of the system is equal to or greater than a preset threshold pressure. When ambient conditions are such that frost is able to form on the outdoor coil, the activity of the pressure limiting circuitry is used to reset the defrost delay time or otherwise inhibit the operation of the defrost control circuitry.

Abstract: In a heat pump system designed for use with a relatively low pressure refrigerant, provision is made, by use of a vapor pressure control system, to use a higher pressure refrigerant without replacement of the indoor coil and the line set. The vapor pressure is sensed during periods of heat pump operation, and when the pressure reaches a predetermined maximum threshold level, the outdoor fan speed is reduced to thereby cause the vapor pressure to be reduced. When the vapor pressure is reduced to a predetermined minimum threshold level, then the fan speed is resumed so as thereby allow the vapor pressure to again be increased.

Abstract: A suction accumulator for use in a heat pump or air conditioning system includes an inlet tube that has a plurality of holes therein. One hole is preferably at the end of the inlet tube while the others are preferably of decreasing size and spaced apart from near the bottom of the accumulator upward along the inlet tube. Such an arrangement ensures that a vapor/liquid mixture of refrigerant and lubricant entering the accumulator does not cause excessive foaming during normal operation while quickly destratifying a stratified mixture that frequently occurs during periods of system inactivity or floodback.

Abstract: The present invention relates to a method for alleviating a short-term "cold blow" effect in a heat pump heating system. According to a method of the invention, reversing of a system valve in response to the sensing of a defrost condition is delayed by a predetermined time. The amount of this delay time depends upon the amount of time required for a supplementary heating unit to achieve an output sufficient to offset the cooling effect resulting from there being a cold indoor coil.

Abstract: To prevent refrigerant leakage when operating in a metering mode, a refrigerant expansion device, designed to selectively operate in either the meteting or bypass mode of operation, has a cylindrical ring installed to tightly hold the meteting piston in its metering position so as to prevent leakage ofrefrigerant therearound.

Abstract: A method is described of selectively varying the speed of the indoor blower of a heat pump for heating a building or other indoor area when ambient temperature drops below a predetermined level, in order to reduce the cold blow effect of air entering the building. The operating run time fraction of a heating cycle is determined, and the speed of the indoor blower is adjusted when the run time fraction crosses a predetermined threshold value, except that the speed of the indoor blower is maintained when the run time fraction is sufficiently changed compared with a previous run time fraction.

Abstract: A method of controlling a current defrost cycle for an outdoor coil of a heat pump system, the heat pump system having a plurality of supplemental heating elements for heating an air stream passing from an indoor coil to an air supply duct during defrost operation, wherein an initial quantity of supplemental heating elements energized is a function of a most recent previous defrost cycle. The initial quantity of supplemental heating elements is energized upon initiation of a defrost cycle. Whether the initial quantity of supplemental heating elements provided is insufficient or excessive is determined. At least one of the supplemental heating elements is deactivated if the initial quantity of supplemental heating elements being provided is excessive.