Abstract:
A hybrid space and water heating heat pump system includes a heat pump including an outdoor assembly and an indoor assembly; a hot water module including a first heat exchanger, a controller, and a water pump connected to a water line, the first heat exchanger being configured for heating water; and a water heater in fluid communication with the hot water module, the water heater configured for receiving heated water from the first heat exchanger; wherein the controller is configured to select between one of conditioning an interior space or heating of the water in the first heat exchanger; and wherein the heat pump is configured for circulating a refrigerant through a first refrigerant circuit in response to the conditioning of the interior space and circulating the refrigerant through a second refrigerant circuit in response to the heating of the water in the first heat exchanger.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional patent application Ser. No. 61/554,651 filed Nov. 2, 2011, the entire contents of which of incorporating herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to a hybrid heat pump system and, more particularly, to a hot water module coupled to an existing heat pump system and water heater for supplementing the heating needs of the water heater when the heat pump system is not providing space heating or cooling. 
       DESCRIPTION OF RELATED ART 
       [0003]    Reversible heat pumps are commonly used for cooling and heating a climate controlled comfort zone such as a residence or a building. A conventional heat pump includes a compressor, a suction accumulator, a reversing valve, an outdoor heat exchanger with an associated outdoor fan, an indoor heat exchanger with an associated indoor fan, an expansion device operatively associated with the outdoor heat exchanger and a second expansion device operatively associated with the indoor heat exchanger. The heat pump components are typically arranged in a closed refrigerant circuit pump system employing a refrigerant vapor compression cycle. When operating in the cooling mode, excess heat absorbed by the refrigerant in passing through the indoor heat exchanger is rejected to the environment as the refrigerant passes through the outdoor heat exchanger. 
         [0004]    A typical water heater for residential hot water production and storage is the electric resistance water heater and storage tank, although gas water heaters are also used to heat water in the storage tank. Water heaters typically include a tank defining a chamber for retention of water. A water inlet pipe that is provided with a first connection for interconnection with a cold water supply line that conveys fresh relatively cold water into the chamber. Within the tank there are electric resistance elements that heat the water in the tank in the case of electric resistance water heaters. 
         [0005]    An alternative method of heating a liquid have been provided in the form of a desuperheater heat pump water heater to intercept the superheated hot gas from the compressor to provide the auxiliary heating to the water heater. The desuperheater is provided with a water heater or as an accessory in order to intercept the superheated gas from a compressor during the cooling mode. However, the desuperheater water heater is limited in its capacity to heat water as it only does so while there is a demand for space cooling. 
       BRIEF SUMMARY 
       [0006]    According to one aspect of the invention, a hybrid space and water heating heat pump system includes a heat pump including an outdoor assembly and an indoor assembly; a hot water module including a first heat exchanger, a controller, and a water pump connected to a water line, the first heat exchanger being configured for heating water; and a water heater in fluid communication with the hot water module, the water heater being configured for receiving the heated water from the first heat exchanger; wherein the controller is configured to select between one of conditioning an interior space or heating of the water in the first heat exchanger; and wherein the heat pump is configured for circulating a refrigerant through a first refrigerant circuit in response to the conditioning of the interior space and configured for circulating the refrigerant through a second refrigerant circuit in response to the heating of the water in the first heat exchanger. 
         [0007]    According to another aspect of the invention, a method for controlling space and hot water heating with a hybrid heat pump system having a heat pump coupled to a hot water module and a hot water heater, includes receiving, via a sensor, a control signal indicative of a call for the hot water heating; determining, via a controller, whether the heat pump is being used for conditioning an interior space; and switching, via the controller, the heat pump to hot water heating, the switching of the heat pump in response to determining whether to disable the heat pump for conditioning the interior space; wherein the heat pump includes an outdoor assembly and an indoor assembly; wherein the hot water module includes a first heat exchanger, the controller, and a water pump connected to a water line, the first heat exchanger being configured for the hot water heating of water in the first heat exchanger; and wherein the hot water heater being configured for receiving heated water from the first heat exchanger. 
         [0008]    Other aspects, features, and techniques of the invention will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0009]    Referring now to the drawings wherein like elements are numbered alike in the Figures: 
           [0010]      FIG. 1  illustrates a schematic view of a hybrid hot water and heating heat pump system according to an embodiment of the invention; 
           [0011]      FIG. 2  illustrates a system for controlling compressor discharge pressure in an exemplary embodiment; and 
           [0012]      FIG. 3  illustrates a system for controlling compressor discharge pressure in an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Embodiments of a high efficiency hybrid space and water heating heat pump system includes a hot water module and a water heater operably coupled to a heat pump for providing auxiliary hot water heating to the water heater by switching the heat pump from either the space heating mode or the space cooling mode to a hot water heating mode. During the hot water heating mode, the heat pump is operated in the heating mode for specifically heating hot water. The hot water module includes a controller for executing algorithms for controlling one or more valves that diverts vapor refrigerant from a compressor located in the heat pump in an outside environment to a hot water refrigerant circuit in order to heat cold water diverted from a hot water heater. Additionally, the controller would execute algorithms to determine whether to switch from either the space-heating mode or the space-cooling mode to a hot water heating mode during a call for hot water. Additional algorithms may also determine the duration for operating the heat pump in the hot water heating mode by receiving information regarding various operating conditions in the system. In embodiments, discrete components such as, for example, open/close relays and temperature switches may also be utilized to implement the switching modes from either the space-heating mode or the space-cooling mode to a hot water heating mode during a call for hot water. 
         [0014]    Referring now to the drawings,  FIG. 1  illustrates an example hybrid space and water heating heat pump system  10  for indoor space heating and cooling in addition to providing hot water heating according to an embodiment of the invention. Particularly, the system  10  includes a heat pump  13  having an outdoor assembly  14  and an indoor assembly  16  operably coupled to a hot water module  12  and a water heater  28 . The outdoor assembly  14  is connected to the indoor assembly  16  via a refrigerant line circuit  36  for conditioning an interior space  5  in the heating and cooling modes. The outdoor assembly  14  is also connected to a hot water module  12  via refrigerant line circuit  34  for providing auxiliary hot water heating to a water heater  28  when the heat pump  13  is not being used to condition the interior space  5 . In the space heating mode, the system  10  includes, in an embodiment, the outdoor assembly  14  having a compressor  18  connected to an outdoor heat exchanger, such as an evaporator  20 , and an expansion device  22 , while the indoor assembly  16  includes an air handler having an indoor heat exchanger such as a condenser  24  coupled to an indoor fan  26 . It is to be appreciated that in the space cooling mode, the cycle is reversed with the condenser and evaporator of the heating mode acting as an evaporator and condenser, respectively. 
         [0015]    In an embodiment, a three-way valve  38  is provided to divert the refrigerant from the compressor  18  to the hot water module  12  through refrigerant line circuit  34  during auxiliary water heating and also to divert the refrigerant from the compressor  18  to the indoor assembly  16  through refrigerant line circuit  36  during the heating and cooling modes when conditioning the interior space  5 . Additionally, a three-way valve  40  is provided to couple the return path of the refrigerant from either of the refrigerant line circuits  34 ,  36  back to the outdoor assembly  14 . It is to be appreciated that two-way valves may be utilized in lieu of the three-way valves  38 ,  40  in order for diverting the refrigerant in the refrigerant line circuits  34 ,  36  without departing from the scope of the invention. It is also to be appreciated that the hot water module  12  is connected to the refrigerant line in parallel with the indoor assembly  16  in order to receive the refrigerant from the heat pump  13  during conditioning of the interior space  5  or to receive the refrigerant from the heat pump  13  in order to provide auxiliary heating of the water in the water heater  28  during a call for hot water. 
         [0016]    Also shown in  FIG. 1 , hybrid space and water heating heat pump system  10  includes a hot water module  12  connected to hot water heater  28  via a water line  30  for providing auxiliary hot water heating according to an embodiment. Particularly, hot water module  12  includes a refrigerant-to-water heat exchanger  42 , a water pump  32 , a controller  44 , and three-way valves  46 ,  48  connected to the water line  30 , and temperature sensors (not shown) for providing signals of temperature sensed by the various components of the system  10  during space heating or cooling and hot water heating in an embodiment. In another embodiment, two-way valves may be utilized for the three-way valves  46 ,  48  without departing from the scope of the invention. In an embodiment, the controller  44  includes a microprocessor preprogrammed with software programs stored in nonvolatile memory for executing algorithms to provide the system  10  with a variety of operation modes and control sequences that provides auxiliary water heating to the water heater  28  as well as space heating and cooling of the interior space  5  with desired enhanced operational flexibility and efficiency. Based upon a network of sensory inputs sensing several parameters, the microprocessor may, in embodiments, selectively operate the outdoor assembly  14 , indoor assembly  16 , and hot-water module  12 , as programmed to obtain the most efficient balance between demands placed on the system  10 . In another embodiment, the controller  44  may provide control sequences by opening or closing temperature switches and relays coupled to the system  10 , which provides the system  10  with a variety of operation modes and control sequences without requiring the preprogrammed software programs implemented by the microprocessor. The controller  44  controls each of the three-way valves  46 ,  48  to divert water from the water heater  28  through the water line  30  and to the heat exchanger  42 . The heat exchanger  42  effects a heat transfer to the water via the high-pressure vapor refrigerant in the refrigerant line circuit  34  causing the vapor refrigerant to condense into a liquid refrigerant as it releases heat to the water and heats it to a predetermined minimum temperature such as, for example, 120 degrees Fahrenheit. In embodiments, the heat exchanger  42  may be a brazed-plate refrigerant-to-water heat exchanger or a coaxial tube-in-tube heat exchanger for transferring heat to water being circulated between a storage tank in water heater  28  and water module  12 . In embodiments, the water heater  28  may also include electric heating elements or gas heating elements (not shown) to heat the water when the heat pump is not available for auxiliary hot water heating. It is to be appreciated that the system  10  provides auxiliary hot water heating by operating the heat pump in the heating mode and diverting the high-temperature vapor refrigerant through the three-way valve  38  and to the hot water module  12 . It is also to be appreciated that the controller  44  includes algorithms for determining whether to divert vapor refrigerant, from the indoor assembly  16  necessary for the heating- or the cooling modes of interior space  5 , to the hot water module  12  during a call for hot water during the auxiliary heating mode of water in the water heater  28 , as is shown and described below. 
         [0017]    In operation, during the space-heating mode of interior space  5 , the outdoor air passes across evaporator  20  (e.g., via an evaporator fan) causing the low-pressure low-temperature liquid refrigerant to evaporate as it absorbs heat from the outdoor air. The low-pressure refrigerant is delivered to compressor  18  where it is compressed to a high-pressure, high temperature gas. The controller  44  controls the three-way valves  38 ,  40  to circulate refrigerant through refrigerant line circuit  36  and prevents the refrigerant from being circulated through the refrigerant line circuit  34 . Specifically, the high-pressure, high temperature refrigerant vapor from compressor  18  diverted through refrigerant line circuit  36  by three-way valve  38  and is delivered to condenser  24  where the indoor air passes across condenser  24  (e.g., via the indoor fan  26 ) and condenses the high-pressure vapor refrigerant into a liquid refrigerant as it releases heat to the interior space  5 . The liquid refrigerant exiting indoor heat exchanger  24  is diverted through three-way valve  40  and is delivered to the outdoor heat exchanger  20  through an expansion device  22 . The pressure change caused by the expansion device  22  allows the liquid refrigerant to evaporate at a low temperature outside to achieve a combination of liquid and vapor. In embodiments, the expansion device  22  may be a fixed expansion device such as a piston, or a thermostatic or electronic expansion valve. The refrigerant passes through the expansion device  22  and is again delivered to the outdoor heat exchanger  20  and compressor  18  where it is compressed to a high-pressure, high temperature gas, and delivered to indoor heat exchanger  24  to start the heating cycle again. It is to be appreciated that while the operation of the hybrid heat pump system  10  is shown in the space heating mode, the hybrid heat pump system  10  may also operate in the space-cooling mode via a reversing valve (not shown). In the space-cooling mode of interior space  5 , the cycle is reversed with the condenser and evaporator of the heating mode acting as an evaporator and condenser respectively. 
         [0018]    During hot-water heating in the auxiliary heating mode, the controller  44  executes algorithms for providing hot water heating to the water heater  28  through the refrigerant-to-water heat exchanger  42  while forgoing both the space heating and space cooling modes. The controller  44  forgoes these space conditioning modes in order to maximize the time available for hot water heating without adversely affecting comfort when the space-heating and space-cooling modes are not being used. Particularly, in an example, the controller  44  controls the three-way valves  38 ,  40  to circulate refrigerant through the refrigerant line circuit  34  and prevents the refrigerant from being circulated to the condenser through the refrigerant line circuit  36  when a request for hot water is received by controller during a demand for hot water heating. As such, the controller  44 , during a call for hot water, activates the heat pump  13  for operating in a heating mode and controls the three-way valves  38 ,  40  in order to direct the flow of high-pressure high-temperature refrigerant from compressor  18  to the refrigerant-to-water heat exchanger  42  within refrigerant line circuit  34 , while preventing refrigerant from flowing through the refrigerant circuit  36  heating interior space  5 . Also, the controller  44  activates water pump  32  to divert cold water from the tank in water heater  28  to the heat exchanger  42  via valve  48 . In embodiments, when a call for hot water is received by controller  44  during operation of the heat pump  13  in either the space-heating or space cooling modes, the controller  44  will execute algorithms to determine whether to shut-off space-heating or space cooling while diverting the system in order to provide auxiliary hot water heating to the water heater  28  thereby enhancing the operational efficiency of the system  10 . Additional algorithms determine whether to select the space-heating or space cooling modes and the hot water heating mode utilizing a timer to alternate between space-heating or space cooling and hot water heating utilizing, in embodiments, the electric or gas heating elements of the water heater  28  to supplement the hot water demand during. In embodiments, the controller  44  senses the temperature of the interior space  5  and may maintain hot water heating for a predetermined time in order to heat the water to a predetermined minimum temperature if the controller  44  determines that the change in temperature of interior space  5  for the predetermined time may not significantly affect the comfort while the hot water is being heated. 
         [0019]    When operating in the hot water heating mode, recirculating water in refrigerant-to-water heat exchanger  42  increases in temperature. The warmer water in turn causes the refrigerant temperature and pressure to increase as it interacts in the refrigerant-to-water heat exchanger  42 . The increased system pressure drives up the compressor  18  discharge pressure which is a concern for compressor reliability. The increasing discharge pressure can negatively impact the efficiency of the system by causing the compressor  18  to be shut down due to high discharge pressure prior to the water being fully heated. This is especially true when the outdoor ambient temperature (OAT) is approximately 80° F. or higher. 
         [0020]    The heat pump hot water heating mode is shut off at a compressor discharge pressure limit (e.g., 600 psi) which may correspond to manufacturer&#39;s recommended maximum compressor discharge pressure. When the heat pump hot water heating mode is shut off, the remaining water heating must be done by backup heaters. Utilizing the backup heaters due to high compressor discharge pressures significantly degrades the overall heating cycle efficiency. 
         [0021]      FIG. 2  illustrates a system for controlling compressor discharge pressure in an exemplary embodiment. To avoid heat pump hot water heating mode shut off, a sensor  50  monitors compressor discharge pressure during heat pump hot water heating mode. When the compressor discharge pressure reaches a discharge pressure limit, some of the refrigerant is allowed to migrate from refrigerant line circuit  34  to the indoor heat exchanger  24 . Controller  44  controls three way valve  38  to allow a small amount of refrigerant vapor to flow to indoor heat exchanger  24  via refrigerant line circuit  36 . This reduces the effective charge level of the hot water heating system and thus reduces the compressor discharge pressure and avoids a compressor shut off. This refrigerant added to the indoor heat exchanger  24  drops in temperature and condenses into liquid, reducing its pressure so that additional refrigerant can be dumped into the indoor heat exchanger  24  if required. 
         [0022]      FIG. 3  illustrates a system for controlling compressor discharge pressure in an exemplary embodiment. The system of  FIG. 3  employs a pressure regulating valve  60  at the refrigerant inlet of the refrigerant-to-water heat exchanger  42 . The pressure regulating valve is coupled to a bypass line  62  that connects to an inlet of the indoor heat exchanger  24 . The pressure regulating valve  60  may be set to vent refrigerant to the bypass line  62  when a certain refrigerant pressure is present (e.g., 600 psi) to prevent shut down of compressor  18 . As noted with reference to  FIG. 2 , an amount of vapor refrigerant is directed to indoor heat exchanger  24 . This reduces the effective charge level of the hot water heating system and thus reduces the compressor discharge pressure and avoids a compressor shut off. 
         [0023]    The technical effects and benefits of embodiments relate to a high efficiency hybrid space and water heating heat pump system including a hot water module and a water heater operably coupled to the heat pump for providing auxiliary hot water heating to the water heater during operation of the heat pump in the heating mode while forgoing space heating or space cooling of an interior space. The hot water module includes a controller for executing algorithms for controlling one or more valves that diverts vapor refrigerant from a compressor located in the heat pump in an outside environment to a hot water refrigerant circuit in order to heat cold water diverted from the hot water heater. 
         [0024]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. While the description of the present invention has been presented for purposes of illustration and description, it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications, variations, alterations, substitutions, or equivalent arrangement not hereto described will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. Additionally, while various embodiment of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.