Patent Publication Number: US-2012042673-A1

Title: Heat pump

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of the Patent Korean Application No. 10-2010-0079198, filed on Aug. 17, 2010, which is hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND 
     1. Field 
     A heat pump is disclosed herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein: 
         FIG. 1  is a block view of a heat pump according to an embodiment; 
         FIG. 2  is a detailed diagram of the heat pump of  FIG. 1 ; 
         FIG. 3  is a diagram illustrating a flow of water and refrigerant in one operation mode of the heat pump of  FIG. 1 ; 
         FIG. 4  is a diagram illustrating a flow of water and refrigerant in another operation mode of the heat pump of  FIG. 1 ; 
         FIG. 5  is a diagram illustrating a flow of water and refrigerant in a further operation mode of the heat pump of  FIG. 1 ; 
         FIG. 6  is a diagram illustrating a flow of water and refrigerant in a still further operation mode of the heat pump of  FIG. 1 ; 
         FIG. 7  is a flow chart illustrating a minimum pricing operation mode as a control method for a heat pump according to an embodiment; and 
         FIG. 8  is a flow chart illustrating a peak pricing rate operation mode as a control method of the heat pump according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, a heat pump refers to a cooling/heating device that changes a low temperature heat source into a high temperature heat source and vice versa using heat or condensation heat of refrigerant, as a transport. The heat pump may include an outdoor unit or device having a compressor and an outdoor heat exchanger, and an indoor unit or device having an expansion valve and an indoor heat exchanger. 
     When the heat pump is used for heating a room, the heat pump may replace fossil fuel. However, if a temperature of external air drops, heating efficiency may deteriorate drastically or a sufficient heating function might not be provided in a case that the heat pump is used as a heating source. As a result, the heat pump often alone cannot provide sufficient heating or quick-hot-water-supply. 
     Also, the heat pump and a boiler may be used together for heating. In this case, when a power rate or gas rate per unit heat quantity is changed, methods for minimizing a total rate of energy consumed for heating may be required. 
     Embodiments disclosed herein provide a heat pump that can be operated in communication with a boiler, selectively, based on a temperature of external air or an electric power rate per unit heat quantity, to provide a radiation heating operation. 
       FIG. 1  is a block view of a heat pump according to an embodiment. The heat pump  1000  of  FIG. 1  may include an outdoor unit or device (O) configured to compress refrigerant; a hydro-unit or device (H) configured to heat-exchange the compressed refrigerant with water; a boiler  700  configured to heat circulating water or water supplied from a commercial water supply system; a quick-hot-water-supply unit or device  900  configured to receive the water having passed through the boiler  700 ; a radiating heater  600  configured to heat a floor of a room by circulating the water having passed through the hydro-unit (H) or both the hydro-unit  600  and the boiler  700 , and a control part or controller configured to control the outdoor unit (O), the hydro-unit (H), and the boiler  700 . 
     When the heat pump  1000  is used for heating a room, the outdoor unit (O) may supply the refrigerant compressed by a compressor. In a case in which the indoor unit (I) is provided, the outdoor unit (O) may heat or cool a room, which is a conditioning object, based on a user&#39; request. 
     The hydro-unit (H) may heat-exchange the refrigerant supplied from the outdoor unit (O) with the water circulating through the radiation heater  600 . For convenience of explanation,  FIG. 2  illustrates the radiation heater  600  as including a floor heating pipe, that is radiation heater pipe  610  that heats a floor of a room. Such a radiation heater having the floor heating pipe will be used as an example. More specifically, the radiation heater  600  radiates the heated water that heats the room. The radiation heater  600  may be a floor heating pipe or a radiator. 
     As a result, radiation heating is provided using the heat generated in a process of condensing refrigerant. However, if a temperature of external air falls to a preset or predetermined temperature below approximately zero degrees, the efficiency of the radiation heating function gained by the heat exchange between the refrigerant and the water may deteriorate drastically. Because of this, the heat pump  1000  according to an embodiment may further include the boiler  700 . 
     The boiler  700  may also provide a heating function, like the hydro-unit (H). The boiler  700  and the hydro-unit (H) may be selectively operated based on the temperature of the external air and a gas rate billed by unit heat amount or the power rate. 
     In addition, when the temperature of the external air is equal to or less than the preset or predetermined temperature in a case in which the boiler  700  is not operated, the water circulating through the hydro-unit (H) and the radiation heater  600  may pass through the boiler  700  to prevent the boiler  700  from freezing and bursting. 
     The heat pump  1000  according to an embodiment may receive information on power rates or gas rates from an energy management device (E) provided in a house under a Smart Grid environment in real time or periodically. The control part or controller of the hydro-unit (H) may control the hydro-unit (H), the boiler  700 , or the outdoor unit (O) based on the received information or stored information on the power rates. 
     The heat pump according to embodiments is shown as a heat pump including the outdoor unit (O), the hydro-unit (H), and the boiler  700 . The outdoor unit (O), the hydro-unit (H), and the boiler  700  may be controlled by the control part of the heat pump, or by an energy management system (EMS) connected with the control part of the heat pump so as to be able to communicate with the control part. 
     The control part of the heat pump may be connected with the energy management system (EMS) of a Smart Grid. The control part may be provided in the hydro-unit (H), and the hydro-unit may be connected to and communicate with the outdoor unit (O), the hydro-unit (H), and the boiler  700 . The outdoor unit (O) and the hydro-unit (H) may be connected to each other by a refrigerant pipe (R). The hydro-unit (H), the radiation heater  600 , and the boiler  700  may be connected with each other by a water pipe (W) through which water may flow. 
     Hot water may be supplied to a user by the quick-hot-water-supply unit  900  after the boiler  700  is selectively operated. 
       FIG. 2  is a detailed diagram of the heat pump of  FIG. 1 . The air conditioning operation performed by the heat pump  1000  of  FIG. 2  may include a heating operation that heat-air-conditions a room, which is an air-conditioning object, by sucking internal air, and a cooling operation that cool-air-conditions a room, which is an air-conditioning object, by sucking internal air. 
     An accumulator  110  may be installed in an inlet passage  22  of the compressor  120  provided in the outdoor unit (O) to prevent liquid refrigerant from flowing into the compressor  120 . An oil separator  130  may be installed in an outlet passage  26  of the compressor  120  to separate oil from refrigerant and oil exhausted from the compressor  120  and return the oil to the compressor  120 . The outdoor heat exchanger  140  may condense or evaporate refrigerant while heat-exchanging it with external air. The outdoor heat exchanger  140  may be an air refrigerant heat exchanger capable of heat-exchanging refrigerant with the external air, or it may be a water refrigerant heat exchanger capable of heat-exchanging cooled water with the refrigerant. In the following description of an embodiment, the outdoor heat exchange  140  is embodied as an air refrigerant heat exchanger that heat-exchanges external air with refrigerant for convenience of explanation; however, embodiments are not so limited. When the outdoor heat exchanger  140  is configured as an air refrigerant heat exchanger, an outdoor fan  150  may be installed to blow external air to the outdoor exchanger  140 . 
     The outdoor heat exchanger  140  provided in the outdoor unit (O) may be connected with an indoor heat exchanger  320  provided in the indoor unit (I) by a heat exchanger connection pipe  32 . Expansion devices  210  and  310  may be provided in the heat exchanger connection pipe  32 . The expansion devices  210 ,  312  may include an outdoor expansion device  210  installed adjacent to the outdoor heat exchanger  140  and an indoor expansion device  310  installed adjacent to the indoor heat exchanger  320 . 
     The heat exchanger connection pipe  32  may include an outdoor heat exchanger-outdoor expansion device connection pipe  34  that connects the outdoor heat exchanger  140  with the outdoor expansion device  210 , an expansion device connection pipe  36  that connects the outdoor expansion device  210  with the indoor expansion device  310 , and an indoor expansion device-indoor heat exchanger connection pipe  38  that connects the indoor expansion device  310  with the indoor heat exchanger  320 . 
     The indoor heat exchanger  320  may be a heat exchanger configured to cool or heat the room by heat-exchanging internal air with refrigerant. An indoor fan  39  may blow internal air to the indoor heat exchanger  320 . 
     As a result, in a case in which the heat pump  1000  is operated in a cooling mode for cooling the room via the indoor unit (I), the refrigerant compressed in the compressor  120  of the outdoor unit (O) may pass through the outdoor heat exchanger  140 , the expansion devices  210  and  310 , and the indoor heat exchanger  320  sequentially, to be collected in the compressor  120 . Thereafter, the refrigerant collected in the compressor  120  may be evaporated by the indoor heat exchanger  320  employed as an evaporator. In a case that the heat pump  1000  is operated in a heating mode for heating the room via the indoor unit (I), the refrigerant compressed in the compressor  120  of the outdoor unit (O) may pass through the indoor heat exchanger  320 , the expansion devices  210  and  310 , and the outdoor heat exchanger  140  sequentially, to be collected in the compressor  120 . Thereafter, the refrigerant may be condensed by the indoor heat exchanger  320  employed as a condenser. 
     The outdoor unit (O) may be an air conditioner with both heating and cooling functions that passes the refrigerant compressed in the compressor  120  through the outdoor heat exchanger  140 , the expansion devices  210  and  310 , and the indoor heat exchanger  320  sequentially before collecting it in the compressor  120 , in a heating mode, and that passes the refrigerant through the indoor heat exchanger  320 , the expansion devices  210  and  310 , and the outdoor heat exchanger  140  sequentially before collecting it in the compressor  120 , in a cooling mode. The outdoor unit (O) may further include a heating/cooling direction control valve  190  that directs the refrigerant to flow through the compressor  120 , the outdoor heat exchanger  140 , the expansion devices  210  and  310 , and the indoor heat exchanger  320  sequentially, or to flow through the compressor  120 , the indoor heat exchanger  320 , the expansion devices  210  and  310 , and the outdoor heat exchanger  140  sequentially. The heating/cooling direction control valve  190  may be connected with the compressor  120  via the compressor inlet passage  22  and the compressor outlet passage  26 , and it may be connected with the outdoor heat exchanger  140  via the outdoor heat exchanger connection pipe  42 . It may also be connected with the indoor heat exchanger  320  via the indoor heat exchanger connection pipe  44 . 
     The outdoor unit (O) may include a refrigerant control valve  170  that supplies the refrigerant supplied via the compressor outlet passage  26  toward the hydro-unit (H) or the heating/cooling direction control valve  190  selectively. The refrigerant control valve  170  may be a 3-way valve. When the refrigerant control valve  170  is a 3-way valve, it may be provided in the compressor outlet passage  26 , and a hydro-unit supply passage  52  may be branched to supply the refrigerant toward the hydro-unit (H). 
     In addition, the outdoor unit (O) may include an auxiliary refrigerant control valve  180 . The auxiliary refrigerant control valve  180  may be used to supply the refrigerant to a heat exchanger bypass passage  8 , which will be described hereinafter, or toward the heating/cooling direction control valve  190 . The auxiliary refrigerant control valve  180  may be a 3-way valve. When the auxiliary refrigerant control valve  180  is a 3-way valve, it may be installed in a hydro-unit collection passage  54  connected with the compressor outlet passage  26  that collects the refrigerant in the hydro-unit (H) and the heat exchanger bypass passage  8  may be branched therefrom. 
     The heat exchanger according to embodiments may further include a heat exchanger bypass valve  230  installed in the heat exchanger bypass passage  8  that controls the flow of the refrigerant, and a liquid refrigerant valve  240  installed between the heat exchanger bypass passage  8  and the indoor expansion device  310  that controls the flow of the refrigerant. 
     The heat pump  1000  according to embodiments may include the hydro-unit (H) to heat-exchange the refrigerant supplied by the outdoor unit (O) with water for radiation heating. The hydro-unit (H) may further include the hydro-unit heat exchanger  530  to heat-exchange the refrigerant with water. 
     The hydro-unit heat exchanger  530  may be provided in a hydro-unit circulation passage  50  of the outdoor unit (O) to condense, expand, and evaporate the refrigerant used in the quick-hot-water-supply unit after exhausted from the compressor  120 . The hydro-unit circulation passage  50  may include a hydro-unit supply passage  52  through which the refrigerant of the outdoor unit (O), in particular, the refrigerant compressed in the compressor  120 , flows to the hydro-unit heat exchanger  530 , and a hydro-unit collection passage  54  through which the refrigerant exhausted from the hydro-unit heat exchanger  530  flows to the outdoor unit (O), in particular, the heating/cooling direction control valve  190 . 
     An end of the hydro-unit supply passage  52  may be connected with the refrigerant control valve  170  provided in the compressor outlet passage  26  and the other end may be connected with the hydro-unit heat exchanger  530 . An end of the hydro-unit collection passage  54  may be connected with hydro-unit heat exchanger  530  and the other end may be connected with the compressor outlet passage  26 . 
     When the refrigerant control part or controller  6  controls the refrigerant to flow to the hydro-unit heat exchanger  530 , the hydro-unit heat exchanger  530  may function as a desuperheater that condenses the refrigerant overheated in the compressor  120  by heat-exchanging it with the water used for radiation heating. 
     The hydro-unit heat exchanger  530  may have a refrigerant passage through which the overheated refrigerant flows and a passage through which the water used for the radiation heating flows. The hydro-unit heat exchanger  530  may be a double-pipe type heat exchanger having a heat transfer member located between the refrigerant passage and the water passage, which may be formed in internal and external areas thereof, or alternatively, it may be a plate type heat exchanger which has the heat transfer member located between the refrigerant passage and the water passage. 
     The radiation heater  600  may be a radiator or a heating pipe for heating a floor, which are installed in a room. 
     With the heat pump  1000  according to embodiments, the hydro-unit heat exchanger  530  may be connected with the radiation heater  600  installed in the floor of the room by a floor supply pipe  82  and a floor collection pipe  83 . A floor heating pump  550  may be installed in the floor collection pipe  83 . 
     For explanation convenience, the radiation heater part  600  is shown installed in the floor of the room and connected with the hydro-unit heat exchanger  530  by the floor supply pipe  82  and the floor collection pipe  83  with the floor heating pump  520  installed in the floor collection pipe  83 ; however, embodiments are not limited to this configuration. 
     The heat pump  1000  according to embodiments may further include the boiler  700  as a means for providing a heat source used in heating or quick-hot-water-supply, rather than the hydro-unit (H). 
     When the external temperature is equal to or less than a preset or predetermined temperature, efficiency of heating that uses refrigerant may deteriorate drastically. Because of this, when the external temperature drops lower than the preset temperature, the heat pump  1000  may selectively operate the boiler  700  as a heat source for heating. 
     The boiler  700  may include a combustion heating part or heater  720  configured to combust fossil fuels and a heat exchange heating part or heater  710  configured to heat water heated in the combustion heating part  720  using a heat exchange method. The combustion heating part  720  may heat the water supplied via the floor supply pipe  82 . The heat exchange heating part  710  may heat-exchange water supplied from a quick-hot-water tank (not shown), which will be described later, with the water heated in the combustion heating part  720 , to heat the water supplied from the quick-hot-water tank. 
     The floor supply pipe  82  may include a first boiler valve  740  and a second boiler valve  750 . The first boiler valve  740  and the second boiler valve  750  may be provided in the floor supply pipe  82 , with a boiler supply pipe  84  and a boiler collection pipe  85  connected thereto, respectively. The boiler supply pipe  84  and the boiler collection pipe  85  may be pipes that pass through the boiler  700 . The boiler supply pipe  84  and the boiler collection pipe  85  may guide the water circulating through the hydro-unit (H) to pass through the combustion heating part  720  provided in the boiler  700 . The first boiler valve  740  and the second boiler valve  750  may directly supply the water supplied from the hydro-unit (H) to the radiation heater  600 , or they may selectively shut off the passage so that the water flows through the combustion heating part  720  of the boiler  700 . 
     The water may be supplied from the hydro-unit (H) to pass through the boiler  700 , which it will be described in detail later, to prevent the boiler  700 , which is not being operated, from freezing or bursting, or to operate the boiler  700 . Water supplied from a commercial water supply (CW) may pass through a boiler passing pipe  60  and the heat exchange heating part  710 , to be selectively heated based on an operation state or a standby state of the boiler.  FIG. 3  illustrates a flow of water and refrigerant in one operation mode of the heat pump of  FIG. 1 .  FIG. 3  illustrates an operation mode for controlling the heat pump  1000  to perform a floor heating function of  FIG. 1 . For explanation convenience, it is shown that the indoor unit (I) is not operated. When the temperature of external air is equal to or greater than a preset or predetermined second temperature above freezing, the heat pump  1000  according to embodiments may be controlled to perform the floor heating function. 
     The preset second temperature above zero degree, which is a point of freezing, may be equal to or greater than approximately 3° C. equal to or less than approximately 7° C. For example, the preset second temperature may be approximately 5° C. 
     The heat pump  1000  according to embodiments may include the boiler  700 . When the temperature of the external air is equal to or greater than the second temperature, the boiler  700  need not be operated. This is because the heat exchanging between the water and the refrigerant in the hydro-unit (H) can supply sufficient radiation heating. 
     The heat pump  1000  according to embodiments may perform the radiation heating operation by controlling the hydro-unit (H), the refrigerant condensed in the heat exchanger of the hydro-unit being supplied to the outdoor unit (O). 
     The refrigerant supplied to the outdoor unit (O) may be supplied to the outdoor heat exchanger  140 . Thereafter, the refrigerant may be expanded in the outdoor expansion device  210  and evaporated in the outdoor heat exchanger  140 . The refrigerant evaporated in the outdoor heat exchanger  140  may be supplied to the compressor  120 . 
     The heating/cooling direction control valve  190  may supply the refrigerant evaporated in the outdoor heat exchanger  140  to the compressor  120 , via the accumulator  110  provided at a front end of the compressor  120 . The refrigerant compressed in the compressor  120  may then be supplied to the compressor outlet passage  26  via the oil separator  130 . 
     The refrigerant compressed in the compressor  120  may be supplied to the hydro-unit (H) via the compressor outlet passage  26 . The refrigerant supplied to the hydro-unit (H) via the compressor outlet passage  26  may be supplied to the hydro-unit heat exchanger  530 . Thereafter, the refrigerant may be heat-exchanged with water in the hydro-unit heat exchanger  530 , and the heat-exchanged water may be circulated through the radiation heating pipe  610  of the radiation heater  600 . 
     In other words, the water circulating through the hydro-unit heat exchanger  530  and the heating pipe  610  of the radiation heater  600  may suck heat in the hydro-unit heat exchanger  530  and radiates the heat in the heating pipe  610  of the radiation heater  600 . This process may be repeated. 
     The water circulating through the hydro-unit heat exchanger  530  and the radiation heating pipe  610  of the radiation heater  600  need not pass through the boiler  700 , because the boiler  700  has little possibility of freezing and bursting when the temperature of the external air is equal to or greater than the preset second temperature above approximately 0° C. When a quick-hot-water-supply function or operation is required, an auxiliary quick-hot-water tank may not be necessary. That is, the water supplied from a commercial water supply system (CW) via the commercial water supply pipe  90  may be heated in the heat exchange heating part  730  of the boiler  700 . Thereafter, hot water may be supplied to a user via the quick-hot-water-supply unit  900 . 
       FIG. 4  is a diagram illustrating a flow of water and refrigerant in another operation mode of the heat pump of  FIG. 1 . With reference to  FIG. 3 , repetitive description has been omitted. Similar to the operation mode described with reference to  FIG. 3 , it may be assumed that the indoor unit (I) is not operated and that the floor heating function is provided by the heat pump  1000 . 
     The embodiment of  FIG. 4  shows an operation mode when the temperature of the external air is equal to or greater than a preset or predetermined first temperature below approximately 0° C. and equal to or less than a preset or predetermined second temperature above approximately 0° C. 
     According to the operation mode shown in  FIG. 4 , water heat-exchanged with refrigerant in the hydro-unit heat exchanger  530  may be circulated through the radiation heating pipe  610  of the radiation heater  600 , to heat the floor of the room, which is the same as the operation mode of  FIG. 3 . 
     However, the temperature of the external air may be the preset second temperature above approximately 0° C. The boiler  700  and the pipes therein may freeze and burst due to water remaining in the pipes of the boiler  700 . 
     As mentioned above, when the temperature of the external air is equal to or less than the preset second temperature, the water not circulating but remaining in the pipes of the boiler  700  may freeze and burst. To prevent the freezing and bursting of the boiler  700 , the heat pump  1000  according to embodiments may control or direct the water supplied to the radiation heater  600  to pass through the boiler  700 , regardless of the operation state or the standby state of the boiler  700 , when the temperature of the external air is equal to or less than the preset first temperature. 
     Here, the preset first temperature may be equal to or greater than approximately minus 7 degrees and equal to or less than approximately minus 3 degrees (−7° C.˜−3° C.). For example, when the temperature of the external air is equal to or greater than the preset first temperature, which may be approximately −5° C., the boiler  700  for heating the floor or hot-water-supply may not be operated necessarily and the floor heating may be performed by only the heat exchange performed in the hydro-unit (H). 
     However, as mentioned above, the water supplied to the radiation heater  600  may be controlled to pass through the boiler  700  to prevent the freezing and bursting of the boiler  700 . In this case, the first boiler valve  740  and the second boiler valve  750  may be controlled so that the water heat-exchanged with the refrigerant in the second heat exchanger  730  passes through the boiler  700 , and the floor heating pump  550  may be operated to pump the water circulating through the hydro-unit (H). 
       FIG. 5  is a diagram illustrating a flow of water and refrigerant in a further operation mode of the heat pump of  FIG. 1 . Compared with the description of  FIGS. 3 and 4 , repeated description has been omitted. 
     Like the operation modes mentioned above with reference to  FIGS. 3 and 4 , it may be assumed that the indoor unit (I) is not operated and that the boiler  700  instead of the heat pump  1000  is operated to heat the floor. 
     For example, the preset first temperature may be approximately −7° C. to approximately −3° C. When the temperature of the external air is equal to or less than the first preset temperature, which means it is cold weather in winter, the heating efficiency which uses the heat exchange of the refrigerant may deteriorate drastically and a satisfactory hot-water temperature cannot be reached. As a result, in a case that the temperature of the external air is very low, the operation of the hydro-unit (H) may be stopped and the boiler  700  may be operated. In the case of the floor heating, the water may be circulating along the same passage as the passage of the floor heating shown in  FIG. 4 . In other words, the water circulating through the hydro-unit heat exchanger  530  may be supplied to the radiation heater  600  via the combustion heating part  720  of the boiler  700 . 
     With this embodiment, there is a different feature that the heat source for the floor heating is not the hydro-unit (H), but rather, the boiler  700 . Even when the hydro-unit (H) is not operated, the floor heating pump  550  provided in the floor collection pipe  83  may be operated to circulate the water and the boiler pump  730  provided in the boiler  700  may be operated, too. 
       FIG. 6  is a diagram illustrating a flow of water and refrigerant in a still further operation mode of the heat pump of  FIG. 1 . Like the operation mode shown in  FIG. 3 , the operation mode shown in  FIG. 6  is an operation mode performed when the temperature of the external air is equal to or less than the preset second temperature above approximately 0° C. and equal to or greater than the preset first temperature below approximately 0° C. The operation mode shown in  FIG. 6  is configured to enable the heating function using the indoor unit (I). 
     The heat pump  1000  according to embodiments enables heating using the radiation process and using the indoor unit (I). Considering the capacity of the compressor  120  provided in the outdoor unit (O), both heating processes performed by the outdoor unit (O) may not be sufficient. Because of this, the operation mode shown in  FIG. 6  provides only heating using the indoor unit (I) and floor heating using the radiation process. 
     As a result, the refrigerant control valve  170  controls the refrigerant compressed in the compressor  120  to be supplied to the heating/cooling direction control valve  190 . Since the floor heating function is not provided, the refrigerant compressed in the compressor  120  does not have to be supplied to the hydro-unit (H). The heating/cooling direction control valve  190  may guide or direct the refrigerant supplied from the hydro-unit (H) toward the indoor heat exchanger connection pipe  44  and the refrigerant may be guided or directed by the indoor heat exchanger  320  thereafter. 
     Heating of internal air may be performed by condensing of the refrigerant in the indoor heat exchanger  320 . The refrigerant condensed in the indoor heat exchanger  320  may be supplied to the outdoor heat exchanger  140  via the heat exchanger connection pipe  32  configured to connect the outdoor heat exchanger  140  with the indoor heat exchanger  320 . Thereafter, the refrigerant may be expanded in the expansion devices  210  and  310 . The refrigerant may be evaporated in the outdoor heat exchanger  140  and guided toward the compressor  120  by the heating/cooling direction control valve  190 . 
     The indoor heating performed by the indoor unit (I) may be provided by such an operation mode. 
     This operation mode may be operated when the temperature of the external air is equal to or less than the preset second temperature above approximately 0° C. and equal to or greater than the preset first temperature. To prevent the freezing and bursting, the water circulating between the boiler  700  and the radiation heater  600  has to circulate continuously, even in a state in which the boiler  700  or the hydro-unit (H) is not operated. 
     In this case, the first boiler valve  740  and the second boiler valve  750  provided in the boiler supply pipe  84  may control the water heat-exchanged with the refrigerant in the hydro-unit heat exchanger  530  to flow to the boiler  700 . The boiler pump  730  and/or the floor heating pump  550  may be operated to pump the water circulating through the hydro-unit (H). 
     In addition, when the temperature of the external air is equal to or greater than the preset second temperature above approximately 0° C., there is no danger of the boiler  700  freezing and bursting and only the indoor unit (I) may be operated for heating. When the floor heating function is switched off, the water does not have to circulate between the radiation heater  600  and the boiler  700 . 
       FIG. 7  is a flow chart illustrating a control method for a heat pump according to an embodiment. It may be assumed that a Smart Grid may be used in the environments where the heat pump according to embodiments is used. 
     The Smart Grid may include an electric power station for generating electricity by way of nuclear power generation or hydroelectric power generation, and a solar power station and a wind power station, which use renewable energy, such as sunlight and wind power. The electric power station may transmit electricity to an outdoor station via a power cable and the outdoor station may transmit the electricity to a substation. Here, the electricity transmitted to the substation may be distributed to households and offices via electricity storage devices. 
     Households using a Home Area Network (HAN) may generate and supply electricity using a fuel cell mounted in self-solar power generation facilities or in Plug-in Hybrid Electric Vehicle (PGEV), and they may sell remaining electricity to others. With a smart metering infrastructure, an office or household may recognize the electric power and power rates used therein in real time. Because of this, a user may recognize current electric power and electric rates, and he or she may take measures to reduce power consumption or power rates depending on the circumstances. 
     The power station, outdoor station, storage device, and consuming places may enable duplex transmission. As a result, the consuming places may not receive electricity unilaterally but may notify their circumstances to the other electric power storage devices, outdoor stations and power stations to implement electricity generation and electricity distribution according to the circumstances. 
     An EMS (Energy Management System) employed for real-time electric power management and real-time power consumption prediction and an AMI (Advanced Metering Infrastructure) for real-time metering of the power consumption may be important in the Smart Grid. Such an EMS and AMI may be independent devices or a single device configured to perform functions of the two devices. 
     The AMI under a Smart Grid is basic technology for integrating consumers based on open architecture and enables the consumers to use electricity efficiently and electric power suppliers to manage the system by detecting an error in the system. Here, the term “open architecture” may refer to all kinds of electric appliances connected to each other in a Smart Grid, regardless of manufacturers thereof, in comparison to a conventional communication network. 
     As a result, the metering infrastructure used in the Smart Grid may make possible consumer-friendly efficiency, such as ‘Prices to Devices’. That is, a real-time price signal of the electric power market may be delivered via an EMS installed in each household and the EMS may communicate with each electric appliances to control the same. As a result, the user may recognize electric power information of each electric appliance after seeing the EMS, and he or she may implement an electric power information process, for example, power consumption or setting of power-rate limit based on the recognized power information. The EMS may include a local EMS used in the offices or household and a center or central EMS for processing information acquired by the local EMS. 
     As real-time communication related to the electric power information between the supplier and consumer is possible in the Smart Grid, “real-time Grid response” may be enabled. For example, the power rate may be differentiated based on time periods or a time of power usage, and a quantity of the power usage may be differentiated in a case in which the power rate bill is different based on the power supply company. In addition, the power supplier may adjust the power rate or the power supply based on the response of the consumers. 
     An electricity supply network system may include a measuring device (i.e., a Smart meter) capable of measuring the electricity supplied to the households and/or the power rate in real time, and an energy management system (E) connected with a plurality of electric devices, such as electric appliances, to control the operation the plurality of the electric devices. 
     The EMS may control each electric appliance based on power rate information directly, or it may provide only the power rate information to each of the electric appliances. In the latter case, a control part or controller of each electric appliance may generate a control signal for the electric appliance based on the information provided by the EMS. 
     As a result, the EMS may provide a control part or controller of a heat pump with information on power rate per unit heat quantity at a preset interval or it may provide the control part with a control signal for the heat pump. The control part of the heat pump may control each of element of the heat pump based on the transmitted control signal. 
     The power rate for each household may be billed on a pay-by-time system. The power rate may be high in hours having increased power consumption and may be low in hours having relatively less power consumption, such as night hours. An energy saving mode may reduce the power consumption, and the energy saving mode may guide or perform a saving mode forcibly, although with hardly different technical effects from the effects of the mode set by the user. 
     Under a Smart Grid according to embodiments, the power rate bill may be variable in a period of a preset date(s), preset week(s), or preset month(s). More particularly, the power rate may be billed differently based in specific hours on a specific date. For example, the power rate may be billed high in an On Peak Time period in which power consumption is large, and it may be billed relatively less high in an “Off Peak” Time period. 
     In addition, under the Smart Grid, the electric power supplier may provide electric power consumers with information on the current power rate billed in each of the periods in real time. 
     The power rate information may be categorized into a schedule information type, which provides the power rate which will be billed after the period to which the current time belongs, or a real time information type, which provides only the power rate billed for the period to which the current time belongs. The former has an advantage of easy expectation of the next power rate. However, it is difficult to determine the power rate after the current time period from the former type, because it does not provide the information on the power rate billed after the current time period. 
     As mentioned above, Smart Grid enables two-way communication between the electric power supplier and the electric power consumer. The electric power supplier may monitor power consumption of the consumer in real time, and it may bill the power rate for the next time flexibly. The electric power consumer may receive the power rate bill in real time, and he or she may postpone a driving time of the electric appliance or stop use of the electric appliance as a result. Because of this, the electric power consumer may save power, and the electric power supplier may distribute the electric power efficiently. 
     Also, the electric power supplier may transmit the power rate information on the power used by the consumer using various schemes. For example, all of the power rate information per preset hour for a preset time period after a preset time period to which the current time belongs, or only power rate information per preset hour for the preset time period to which the current time belongs in real time. 
     In other words, information on the power rate billed in a period of 1 hour or 30 minutes for a specific date, a specific week, or a specific month may be provided in advance. Alternatively, information on the power rate billed for a preset time period to which the current time belongs may be provided in real time. 
     For example, the electric power supplier may send information on the electric power rate to the electric power consumer, such as a household. The power rate information may be configured variously. In other words, the power rate information may be configured of information on the power rate billed for preset hours of a preset time period after receiving the information, or it may be configured of the continuously sent information on the power rate for preset hours in real time. For example, the information on the power rate for the preset hours of the preset time period after the receiving information may refer to the information provided by categorizing the information on the power rate billed for 24 hours after 12 noon or 12 midnight everyday into time bands of an hour or 30 minutes. 
     A control or controller part of such the EMS may be integrally provided with the electric appliance. In this case, an auxiliary power supply independent from a power supply of the electric appliance may be provided, and the EMS may be provided with the electric power constantly, regardless of the power supplied to the electric appliance via the power supply. In this case, the control part may receive not only the power rate billed for the time period to which the current time belongs, but also the information on the power rate billed for each of prior periods to be stored. 
     The heat pump  1000  according to embodiments may use the boiler  700  or the hydro-unit (H) for radiation heating selectively. The hydro-unit (H) may be driven by electricity, like an air conditioner, and the boiler  700  may be driven by fossil fuels. The fossil fuel used to drive the boiler  700  may be gas. 
     As mentioned above, under a Smart Grid according to embodiments, the power rate bill may be variable in a period of a specific date, a specific week, or a specific month. More particularly, the power rate may be varied in specific hours on a specific date. For example, the power rate may be billed high in the On Peak Time period when power consumption is large, and the power rate may be billed relatively less high in the off peak time period when power consumption is relatively small. 
     In other words, the Smart Grid according to embodiments may be an environment in which the power rate is varied in real time. The gas rate is not so sensitive to variation in the time, compared with the electric power rate. Here, it may be assumed that the gas rate is varied in real time. 
     According to a control method of the heat pump shown in  FIG. 7 , when the heating operation is performed, the power rate and the gas rate billed per unit quantity of heat may be compared with each other. 
     As mentioned above, a household which is a main consumer of the Smart Grid may construct a single electricity supply network system. The electricity supply network system may include a measuring device (i.e., a Smart meter) capable of measuring the electricity supplied to the households and/or the power rate in real time, and the energy management system (E) connected with a plurality of electric devices, such as electric appliances, to control the operation the plurality of the electric devices. The power rate may be billed to the household on a pay-by-time system. The power rate may be high in hours having increased power consumption and the power rate may be low in hours having relatively less power consumption, such as night hours. 
     As a result, the EMS (E) provided in each household may receive information on the electric power rate and/or the gas rate in the pay-by-time basis from an external device. The EMS may provide the heat pump  1000  with the received information on the electric power rate and/or the gas rate per unit heat quantity, or it may directly control the heat pump  1000  according to embodiments. 
     The EMS (E) may include a display configured to display electricity information and/or external environmental information, an input part or device configured to enable the user to operate the EMS (E), a communication unit or device configured to transmit and receive information to and from an external device, and a clock control part or controller. Information on the operation mode selectively input by the user or the electric power rate may be stored in the control part. As a result, when the gas rate billed per unit heat quantity is fixed not varied, the user may directly input the gas rate via the input part of the EMS (E). 
     The plurality of the operation modes may be stored in the control part of the heat pump or the hydro-unit, such that the user may control one of them to be operated. The plurality of the operation modes may include a minimum pricing based operation mode. 
     As shown in  FIG. 7 , when a user starts the floor heating operation, in step S 100 , the control part or controller of the EMS or the control part or controller of the heat pump may determine whether to operate the heat pump  1000  in the minimum pricing operation mode based on the user&#39;s selection or setting, in step S 200 . 
     If the operation mode of the heat pump  1000  is the minimum pricing operation mode based on the result of the determination, the control part of the EMS or the control part of the heat pump may compare the electric power rate per unit heat quantity with the gas rate per unit heat quantity, in step S 300 . 
     If the electric power rate per unit heat quantity is less high than the gas rate per unit heat quantity, in step S 400  based on the result of the determination, the control part of the EMS or the control part of the heat pump may provide the heating function using the hydro-unit (H), without operating the boiler  700 , in step S 500 . If the gas rate per unit heat quantity is less high than the electric power rate per unit heat quantity based on the result of the determination, in step S 400 , the control part of the EMS (E) stops the operation of the hydro-unit (H) and starts the operation of the boiler  700 , to provide the heating function, in step S 600 . 
     When the user does not select the minimum pricing operation mode, the hydro-unit (H) or the boiler  700  may be operated based on the user&#39;s selection or setting to provide the heating function, in step S 700 . 
     When the user selects the minimum pricing operation mode, the electric power rate may be varied in a period of preset hours. Because of this, when the preset hours passes, in step S 900 , the method may return to the process which performs the comparison between the electric power rate per unit heat quantity and the gas rate per unit heat quantity and the process may be repeated. 
     When the user does not select the minimum pricing operation mode, the hydro-unit (H) or the boiler  700  may be operated based on the user&#39;s selection or setting and the heating function may be provided, in step S 700 . In this case, the control part of the EMS or the control part of the heat pump may operate the hydro-unit (H) or the heat pump  1000  based on a range of the temperatures (T o ) of external air, as mentioned above. 
     As mentioned above, the hydro-unit (H) of the heat pump has the characteristic of drastically deteriorating efficiency as the temperature (T o ) of the external air drops. Because of this, when the user selects the heating operation, the temperature (T o ) of the external air as well as the rate per unit heat quantity may be a variably used to determine which one of the hydro-unit (H) and the boiler  700  is operated. 
     In addition, even when the user desires the heating function and even when considering the efficiency of the hydro-unit (H), the user may not want the cost of the heating function to increase too much. As a result, the user may select a peak pricing operation mode, which is different from the minimum pricing operation mode relating to the operation mode shown in  FIG. 7 . 
     In other words, the peak pricing operation mode is performed for the gas rate per unit heat quantity or the electric power rate per unit heat quantity and the efficiency of the hydro-unit (H) not to be higher than a peak of the rate set by the user. 
       FIG. 8  illustrates a flow chart illustrating a peak pricing rate operation mode as a control method of the heat pump according to an embodiment. 
     When the user starts the floor heating operation, in step S 1000 , the control part or controller of the EMS (E) may determine whether to operate the heat pump in the peak pricing operation mode based on the user&#39;s selection or setting, step S 2000 . 
     If the operation of the heat pump  1000  is the peak pricing operation mode based on the result of the determination, the control part of the EMS or the control part of the heat pump may determine whether the electric power rate per unit heat quantity is over the peak rate set by the user, in step S 3200 . In this case, the gas rate per unit heat quantity is regularly lower than the peak rate set by the user. Even if it is variable, the gas rate per unit heat quantity may be set to be lower than the peak rate set by the user. 
     If the electric power rate per unit heat quantity is higher than the peak rate set by the user based on the result of the determination, the boiler  700  may be operated in step S 4200 , the hydro-unit being in standby after its operation is stopped. 
     In contrast, if the electric power rate per unit heat quantity is lower than the peak rate set by the user based on the result of the determination, the temperature (T o ) of the external air is compared with the preset second temperature (T 2 ) above approximately 0° C., in step S 4300 . 
     In this case, even when the electric power rate per unit heat quantity is lower than the peak rate set by the user in a case that the temperature (T o ) of the external air is equal to or less than the preset first temperature (T 1 ) below approximately 0° C., the efficiency of the hydro-unit (H) will deteriorate drastically. Because of this, the operation of the hydro-unit (H) may be stopped and the boiler  700  may be put into operation, in step S 4200 . When the boiler  700  is operated, heating water used for the floor heating may pass through the boiler  700  necessarily, in step S 7300 . 
     When the electric power rate per unit heat quantity is lower than the peak rate set by the user, and the temperature (T o ) of the external air is more than the preset first temperature (T 1 ) below approximately 0° C., the heating operation may be performed using the hydro-unit (H) and the operation of the boiler  700  may be stopped, in step S 5300 . In this case, the control part of the EMS or the control part of the heat pump may compare the temperature (T o ) of the external air with a preset second temperature (T 2 ) above approximately 0° C., in step S 6200 . When the temperature (T o ) of the external air is less than the preset second temperature (T 2 ) above approximately 0° C., the water circulating through the hydro-unit (H) and the radiation heating  600  for the floor heating may be controlled to pass through the boiler  700 , in step S 7500 , even when the boiler  700  is not operated. However, when the temperature (T o ) of the external air is higher than the preset second temperature (T 2 ) above approximately 0° C., there is no danger of freezing and bursting of the boiler  700 , and thus, it is not necessary to control the water circulating in the hydro-unit (H) and the radiation heater  600  to pass through the boiler  700 , in step S 7400 . 
     When the peak pricing operation mode is not selected or set by the user, in step S 2000 , the control part of the EMS may compare the gas rate per unit heat quantity and the electric power per unit heat quantity with each other, in step S 3100 , and the temperature (T o ) of the external air may be compared with the preset first temperature (T o ) below approximately 0° C., in step S 4100 . When the gas rate per unit heat quantity is less than the electric power rate per unit heat quantity, or the temperature (T o ) of the external air is higher than the preset first temperature below approximately 0° C., the operation of the boiler  700  may be stopped and the hydro-unit (H) operated, in step S 5100 . 
     When the temperature (T o ) of the external air is lower than the preset first temperature (T 1 ) below approximately 0° C. based on the result of the comparison, the efficiency of the hydro-unit (H) may deteriorate even with the gas rate per unit heat quantity being higher than the electric power. Because of this, the operation of the hydro-unit (H) may be stopped and the boiler  700  is operated, in step S 4200 . 
     The temperature (T o ) of the external air may be compared with the preset second temperature (T 2 ) above approximately 0° C., in step S 6100 . When the temperature (T o ) of the external air is lower than the preset second temperature (T 2 ) above approximately 0° C., the water circulating through the hydro-unit (H) and the radiation heating  600  for the floor heating may be controlled to pass through the boiler  700 , in step S 7100 , even without operating the boiler  700 , to prevent the freezing and bursting of the boiler  700 . However, when the temperature (T o ) of the external air is higher than the preset second temperature (T 2 ) above approximately 0° C., there is no danger of the freezing and bursting of the boiler  700 . Because of this, the water circulating through the hydro-unit (H) and the radiation heater  600  for the floor heating need not pass through the boiler  700 , in step S 7200 . 
     Embodiments disclosed herein provide a heat pump that may include an outdoor unit or device configured to compress refrigerant; a hydro-unit or device configured to heat-exchange the compressed refrigerant with water; a boiler configured to heat water circulating the hydro-unit or water supplied from a commercial water supply system; a radiation heater part configured to perform heating by using the water heated by the hydro-unit or the boiler; and a control part or controller configured to control the outdoor unit, the hydro-unit and the boiler. 
     The boiler may be operated, when a temperature of external air is equal to or less than a preset or predetermined first temperature below approximately 0° C., and the hydro-unit may be operated, when the temperature of the external air is equal to or greater than the first temperature. Water circulating the radiation heater part after being heat-exchanged with the hydro-unit may pass the boiler, when the temperature of the external air is equal to or less than a preset or predetermined second temperature above approximately 0° C. Water circulating the radiation heater part after being heat-exchanged with refrigerant in the hydro-unit may pass the boiler and only a pump provided in the boiler may be operated, when the temperature of the external air is equal to or more than the preset first temperature below approximately 0° C. and equal to or less than the preset second temperature above approximately 0° C. 
     Water circulating the radiation heater part after being heat-exchanged with refrigerant in the hydro-unit may not pass the boiler, when the temperature of the external air is equal to or greater than the preset second temperature above approximately 0° C. 
     Each of the hydro-unit and the boiler may include at least one pump configured to pump heat-exchanged water. The at least one pump may be operated when the temperature of the external air is equal to or less than the preset second temperature above approximately 0° C. 
     The control part may operate the hydro-unit, when the temperature of the external air is equal to or less than the preset first temperature below approximately 0° C. and when it is determined that the boiler has malfunctioned. When the temperature of the external air is equal to or more than the preset first temperature below approximately 0° C. and when it is determined that the hydro-unit has malfunctioned, the control part may operate the boiler. 
     The first temperature may be equal to or greater than approximately −7° C. (7 degrees below zero) and equal to or less than approximately −3° C. (3 degrees below zero), and the second temperature may be equal to or greater than approximately 3° C. (3 degrees above zero) and equal to or less than 7° C. (7 degrees above zero). 
     The control part may compare an electric power rate per unit heat quantity with a gas rate per unit heat quantity, and the control part may selectively operate the boiler and the hydro-unit based on a result of the comparison to minimize the rates per unit heat quantity. The control part may stop operation of the hydro-unit and operate the boiler, or may stop operation of the boiler and operate the hydro-unit, based on the temperature of the external air. 
     The heat pump may further include a quick-hot-water-supply unit or device configured to receive water heated by the boiler selectively after being supplied from a commercial water supply system. 
     Embodiments disclosed herein further provide a heat pump that may include an outdoor unit or device including an outdoor heat exchanger and a compressor; a hydro-unit or device including at least one heat exchanger configured to heat-exchange refrigerant supplied by the outdoor unit with water; a boiler configured to heat water circulating the hydro-unit or water supplied by a commercial water supply system selectively; a radiation heater part configured to heat a floor by circulating the water having passed the hydro-unit or the hydro-unit and the boiler; and a control part configured to control the outdoor unit, the hydro-unit, and the boiler. 
     A floor supply pipe and a floor collection pipe may be provided to connect the hydro-unit with the radiation heater part. A boiler supply pipe and a boiler collection pipe, which are branched from the floor supply pipe, may be provided to connect the floor supply pipe with the boiler. 
     The boiler may include a combustion heating part or heater configured to heat water supplied to the radiation heater part using combustion heat, and a heat exchange heating part or heater configured to heat water supplied by the commercial water supply system using the water heated by the combustion heating part. The boiler may be connected with the hydro-unit to be able to communicate with the hydro-unit and a control signal of the boiler may be transmitted via the hydro-unit. 
     The control part may be connected to an energy management system configured to receive information on an electric power rate. The energy management system may provide information on the electric power rate per unit heat quantity in a preset period. 
     The control part may include the electric power rate per unit heat quantity with the gas rate per unit heat quantity. The control part may stop operation of the boiler and operate the hydro-unit, when the electric power rate per unit heat quantity is lower than the gas rate per unit heat quantity, and the control part may stop operation of the hydro-unit and operate the boiler, when the gas rate per unit heat quantity is lower than the electric power rate per unit heat quantity. 
     When a user sets a peak rate per unit heat quantity, the control part may compare the electric power rate per unit heat quantity and the gas rate per unit heat quantity with the peak rate per unit heat quantity set by the user, and the control part may operate the boiler only in a period in which the electric power rate per unit heat quantity is higher than the peak rate per unit heat quantity set by the user. 
     When the temperature of the external air is equal to or less than a preset or predetermined first temperature below approximately 0° C. even in a case that the electric power per unit heat quantity is lower than the peak rate per unit heat quantity and the gas rate per unit heat quantity, the control part may stop the operation of the hydro-unit and operate the boiler. 
     The heat pump according to embodiments disclosed herein may include the boiler, and it may be operated in communication with the boiler selectively based on the electric power rate per unit heat quantity. Further, the heat pump according to embodiments disclosed herein may use the boiler when the temperature of the external air is equal to or less than a preset or predetermined temperature. As a result, a sufficient heating function or a sufficient quick-hot-water-supply operation may be provided. 
     Still further, in a case in which a power grid is a Smart Grid is utilized, the heat pump according to embodiments disclosed herein may operate the boiler or the hydro-unit of the heat pump selectively based on the electric power rate per unit heat quantity. As a result, a cost of the heating or quick-hot-water supply may be minimized. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in embodiments as broadly described herein without departing from the spirit or scope of the embodiments as broadly described herein. Thus, it is intended that the embodiments as broadly described herein covers the modifications and variations of this embodiments as broadly described herein provided they come within the scope of the appended claims and their equivalents. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.