Method and apparatus for eliminating unnecessary defrost cycles in heat pump systems
AssigneeCarrier Corporation
InventorDon A. Schuster
Life of this patent
Estimating the term…
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.
Claims19
In an apparatus for use in a heat pump system of the type including a compressor, an outdoor unit having an outdoor coil and an outdoor fan, an indoor unit having an indoor coil and an indoor fan, and a liquid line and a vapor line for connecting said indoor and outdoor coils and said compressor in a closed fluidic path, said heat pump system being adapted to operate in any of a cooling mode, a heating mode and a defrosting mode, in combination:
- (a.) a defrost condition detecting device, connected to the outdoor coil, for detecting the occurrence of a frost forming condition at the outdoor coil;
- (b.) a control circuit for controlling the operation of said outdoor unit, said control circuit including:
- (i) pressure limiting circuitry, responsive to one of the pressure and temperature of the refrigerant fluid in said vapor line, for limiting the pressure within said vapor line to a predetermined safe pressure;
- and
- (ii) defrost control circuitry, responsive to said defrost condition detecting device, for causing the heat pump system to initiate a defrost cycle when said frost forming condition has existed for more than a predetermined time;
- and
- (c.) a defrost inhibiting device for preventing said defrost control circuitry from initiating a defrost cycle when the defrost condition detecting device indicates the occurrence of a frost forming condition merely because of the pressure limiting activity of said pressure limiting circuitry.
A method for eliminating unnecessary defrost cycles in a heat pump system of the type including a compressor, an outdoor unit having an outdoor coil and an outdoor fan, an indoor unit having an indoor coil and an indoor fan, and a liquid line and a vapor line for connecting said indoor and outdoor coils and said compressor in a closed fluidic path, said heat pump system being adapted to operate in any of a cooling mode, a heating mode and a defrosting mode, said method comprising the steps of:
- (a) sensing one of the pressure and temperature of the refrigerant fluid in said vapor line to determine the pressure within said vapor line;
- (b) decreasing the speed of said outdoor fan as necessary to limit the pressure in said vapor line to a predetermined maximum pressure;
- (c) detecting the existence of a frost forming condition at the outdoor coil;
- (d) initiating a defrost cycle when said frost forming condition has existed at said outdoor coil for more than a predetermined delay time;
- and
- (e) restarting said predetermined delay time when said frost forming condition exists because of the performance of said speed decreasing step.
In an apparatus for use in a heat pump system of the type including a compressor, an outdoor unit having an outdoor coil and an outdoor fan, an indoor unit having an indoor coil and an indoor fan, and a liquid line and a vapor line for connecting the coils of said indoor and outdoor units and said compressor in a closed fluidic path, said heat pump system being adapted to operate in any of a cooling mode, a heating mode and a defrosting mode, in combination:
- (a.) pressure indicating means, responsive to one of the temperature and pressure of the refrigerant fluid in said vapor line, for indicating the pressure within said vapor line;
- (b.) temperature sensing means connected to the outdoor coil, said temperature sensing means having a first state indicative of the existence of a frost forming condition when the temperature of the outdoor coil falls below a first predetermined temperature and a second state indicative of the absence of a frost forming condition when the temperature of said coil rises above a second predetermined temperature;
- (c.) control means for controlling the operation of said outdoor unit, said control means including:
- (i) pressure limiting means, responsive to said pressure indicating means, for controllably varying the speed of the outdoor fan and thereby maintaining the pressure within said vapor line at a pressure less than a predetermined maximum pressure;
- and
- (ii) defrost control means, responsive to said temperature sensing means, for causing the heat pump system to initiate a defrost cycle when said temperature sensing means assumes and remains in said first state for a delay time equal to or greater than a predetermined delay time;
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- (d.) resetting means for resetting said delay time when said pressure limiting means causes said temperature sensing means to assume said first state, but prevents said temperature sensing means from assuming said second state.
Dependencies are inferred from the claim text.