Abstract: A simplified combustion engine driven heat pump system having electric power co-generation capability includes a compressor unloading valve to reduce demand on the engine and optimize the efficiency of intermittent power generation during heat pump system downtime. Some benefits of electrical power generation available in more sophisticated system designs are thereby obtained with a smaller, simpler, inexpensive and reliable system.

Abstract: A controller for a heat pump system wherein the controller has a variable capacity control capability that responds to thermostat output signals. The variable capacity controller computes real-time performance parameters at variable capacity heating/cooling load conditions of the heat pump system. A defrost controller calculates an optimum heat pump operating time period between successive defrost cycles during a heating mode of the heat pump. Such values are calculated as a function of sensed time, temperature and variable capacity operating conditions which are calculated by the variable capacity controller. The controller preferably has a manual mode for verifying correct operation of each actuator of the heat pump system, as a function of a sequenced input signal, while the heat pump system is in a shutdown mode.

Abstract: A controller for a gas heat pump system wherein the controller has a variable capacity control capability that responds to thermostat output signals. The variable capacity controller computes real-time performance parameters at variable capacity heating/cooling load conditions of the gas heat pump system. A defrost controller calculates a maximum heat pump operating time period between successive defrost cycles and a minimum heat pump operating time period of each defrost cycle, during a heating mode of the gas heat pump. Such values are calculated as a function of sensed time, temperature and variable capacity operating conditions which are calculated by the variable capacity controller. The controller preferably has a manual mode for verifying correct operation of each actuator of the gas heat pump system, as a function of a sequenced input signal, while the gas heat pump system is in a shutdown mode.

Abstract: By sensing the outdoor ambient temperature and the outdoor coil temperature in a heat pump when the outdoor coil is frost-free, a control system determines the split or difference that will later exist between those temperatures (the coil temperature drops as frost accumulates) when sufficient frost has built up on the outdoor coil to necessitate defrosting. When that defrost temperature split, called the Normal Defrost Value or NDV, is exceeded, defrost is initiated and the coil will be defrosted. Since the amount of frost that may have already accumulated on the coil is unknown when the control system is initially powered up (such as when power is restored after an outage), the control system calculates, from the current outdoor ambient temperature, an assumed value for the coil temperature which is likely to exist if the coil were frost-free. The first NDV determined after power up is based on the assumed coil temperature.

Abstract: The current outdoor ambient temperature and outdoor coil temperature in a heat pump are sensed when the heat pump's outdoor coil is clean and frost-free, and from those current temperatures the split or difference that will later exist between the temperatures, when sufficient frost has built up on the outdoor coil to necessitate defrosting, may be determined. When that defrost temperature split, called the Defrost Value or DV, is reached, defrost is initiated and the frost that has accumulated on the coil is melted. Before defrost occurs, however, changing weather conditions (namely, changing outdoor temperature and/or changing outdoor relative humidity) may effectively invalidate the previously determined defrost temperature split or DV, and a frost condition may be reached at a substantially different temperature split, either greater or smaller than that previously calculated.

Abstract: Batch-type water heating apparatus includes a heat exchanger in which water is heated as it is circulated therethrough, a water storage zone, a flow control device, a water pump, and associated water lines connecting these components to form a closed water circulating loop. Additional water lines associated with the flow control device provide for the withdrawal of heated water from the loop and the addition of make-up water to the loop as water is withdrawn therefrom. The flow control device includes a valve and a thermostat for sensing the water temperature at the outlet of the storage zone. The flow control device is operable to position the valve to facilitate withdrawal of heated water from the loop when the sensed temperature exceeds a predetermined value and to position the valve to facilitate circulation of water around the loop when the sensed temperature is below a predetermined value.

Abstract: There is disclosed a heat pump water heater with supplemental heat supply wherein the heat pump is turned on when water has cooled below a predetermined temperature, and is turned off when the water has been heated to a predetermined temperature. In the event frost begins to form on the surface of the heat pump evaporator, the heat pump is turned off and the supplemental heat supply turned on automatically. This condition prevails until the water has been heated to a predetermined temperature, at which time the supplemental heat supply is turned off.

Abstract: A quick recovery heat pump water heater includes a water storage tank with first and second tank portions, and sensing means for indicating the demand for hot water in the tank portions. A water pump and an external heat source are provided. Control means responsive to an indication from the sensing means of a demand for hot water in the first tank portion initially establishes communication of the first tank portion with the pump and external heat source and turns them on. The control means then responds to an indication from the sensing means that the demand for hot water in the first tank portion has been satisfied and establishes communication of the second tank portion with the pump and external heat source. Finally, the control means is responsive to an indication from the sensing means that the demand for hot water in the second tank portion has been satisfied and turns off the pump and external heat source.

Abstract: A refrigerant condensing system for heating water includes a thermostatically-operated valve for delivering 140.degree. F. water from a condenser to the top of a water storage tank and a by-pass valve for allowing the heated water from the condenser, which is then heated to a lower temperature, to flow directly to the bottom of the storage tank after the upper third of the tank has been filled with 140.degree. F. water, thereby increasing the efficiency and heating capacity of the refrigeration system.

Abstract: A control system for a heat pump having at least one stage of supplemental heaters, said control system including an electronic thermostat capable of (1) sensing the rate of change of the temperature in the (indoor) conditioned space; and (2) bringing on supplemental heat, following temperature setup of the thermostat, only if the rate of temperature change is below some predetermined value. A suitable time delay can be built into the control to allow the heat pump to stabilize and therefore give a more realistic indication of the ability of the heat pump to handle a given load.

Abstract: A temperature compensated safety control is employed to shut off the compressor at high compression ratios, caused, for example, by reduced air flow over the condenser or other reasons. This is especially useful on both reverse cycle heat pumps and conventional, non-reversible refrigeration and air conditioning systems to protect the compressor. In a preferred embodiment, the temperature compensation is provided by making the control responsive to outdoor ambient air temperatures.

Abstract: A pressure compensated safety control is employed to shut off the compressor at high compression ratios, caused, for example, by reduced air flow over the condenser or other reasons. This is especially useful on both reverse cycle heat pumps and conventional, non-reversible refrigeration and air conditioning systems to protect the compressor. In a preferred embodiment, the compensation is provided by making the control responsive to compressor suction pressure.

Abstract: A reverse cycle heat pump is provided with a heat exchanger which provides refrigerant subcooling with no thermodynamic losses. The heat exchanger is arranged such that it is operative only during the heating cycle to permit optimum charging of the system and allow operation during the cooling cycle with no excess refrigerant in the system accumulator. The heat exchanger is bypassed when the system is converted from heating to cooling operations.Liquid refrigerant will be mixed with oil in the accumulator during the heating cycle, but not the cooling cycle. Then since refrigerant liquid returning with the oil from the accumulator to the compressor should be evaporated to avoid harm to the compressor, heat applied to the suction line, with no thermodynamic loss, vaporizes this refrigerant. During the cooling operation, no liquid refrigerant is returned from the accumulator, so heat added to the suction gas would be undesirable.