Abstract:
An expandable modular system including standardized dual heat pump modules that are connectable to other standardized heat pump modules. The modules include pumps for a source fluid and for heat transfer fluid that is circulated to a point of use. The heat pump modules are controlled by a dedicated programmable logic controller. The system may be adapted to transfer heat from a source stream that would otherwise be wasted or not utilized for thermal energy rectification. The modules are of limited size to fit through pedestrian doors and are pre-assembled prior to installation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application Ser. No. 62/044,525 filed Sep. 2, 2014, the disclosure of which is hereby incorporated in its entirety by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates to a modular heat recovery system that is scalable by adding additional heat pump modules that are controlled by a power control module and that includes a dual pump module that independently pumps a source stream fluid and a heat transfer fluid through the heat pump modules to a building HVAC system. 
       BACKGROUND 
       [0003]    Heat recovery systems are known and are built as custom installations designed to meet the heating and cooling requirements of a specific building. Custom installations are assembled and connected by piping and wiring that is laid out and installed on-site. The cost of building such systems is a serious disadvantage that adversely impacts cost-benefit analyses, cost savings, and payback analyses. Such systems are also expensive to upgrade to provide additional capacity and/or capacity reduction as the heating and cooling requirements for a building load increase and/or decrease. 
         [0004]    Another problem with custom installations is that they are not readily scalable and are not normally designed to be serviced easily. It is also difficult to service one or more heat pumps while operating the heat recovery system. 
         [0005]    The following patents and published patent applications were considered in conjunction with preparing this disclosure: U.S. Pat. Nos. 3,434,532; 5,339,891; 8,245,491; 8,627,674; and US 2011/0240269. 
         [0006]    The following disclosure is directed to solving the above problems and other problems as summarized below. 
       SUMMARY 
       [0007]    The heat recovery system that is the subject of this disclosure is an expandable modular system that uses standardized dual heat pump modules that are connectable to other standardized modules. The heat pump modules are connected mechanically and electrically and are controlled by a standardized programmable logic controller. The system may be adapted to transfer heat from a source stream that would otherwise be wasted or not utilized for thermal energy rectification. For example, a wastewater treatment effluent flow could be used as the source stream with the heat recovered being used for heating, cooling and/or dehumidification of a building. 
         [0008]    The system is packaged to be easily installed as a plurality of modules in buildings through conventional sized pedestrian doorways. Pedestrian doorways are distinguished from other doorways that may be garage or loading dock doorways by specifying that pedestrian doorways are less than one meter in width and less than 3 meters in height. The ideal location for installing a waste heat recovery system may be only accessible through one or more pedestrian doors in many buildings. Large systems cannot fit through pedestrian doors and must be provided as smaller component parts that are assembled as a custom system that is built on site. Alternatively, the walls of the building may be removed and replaced. Either of these approaches adds unnecessary cost and discourages the use of waste heat recovery systems. 
         [0009]    The system includes three systems that are combined in a standardized module—a heat pump system, a pump system for a source fluid and a heat transfer fluid, and a power/control system. The piping and wiring between the systems is standardized to facilitate easy installation. The standardized modules may be combined with other standardized modules to provide a scalable waste heat recovery system for buildings that have a wide range of heat or cooling requirements. 
         [0010]    The heat pump modules are packaged as stand-alone modules that may be independently installed and/or installed with a plurality of additional modules. Standardized input and output connectors for mechanical and electrical controls allow for expansion of the system by adding additional heat pump modules, as required. The connectors are located to allow for additional modules to be attached to a pre-existing system as well. As an alternative, the heat pump modules may be provided with air-to-air and/or water-to-air heat exchange systems that could be capable of capturing heat from heated air that may be used to augment existing HVAC systems to satisfy heating and cooling loads. 
         [0011]    The dual pump module serves the dual functions of pumping the source stream and the heat transfer fluid. The source stream may be any source of flowing fluid (e.g. water) from which heat is extracted. For example, the source stream may be waste water effluent that has a substantial amount of thermal energy that is normally wasted. The heat transfer fluid (e.g. water, ethylene glycol or propylene glycol) is pumped from the heat pump module to a space conditioning point of use in a building, such as an air handling unit or hydronic conditioning coil for space conditioning purposes. The dual pump module may accommodate varied pump and fluid transfer requirements. The dual pump module also houses an expansion tank for maintaining consistent heat transfer fluid pressure within the operating system. 
         [0012]    The power control module features an integrated electrical power supply and electronic control system. The power control module is adapted to be directly connected to the heat pump modules and the dual pump module. The control system interconnects and coordinates the heat pump modules and the dual pump module using standardized interfaces. The power control module may be connected to the host facility power supply, as well as heating and air conditioning system controls and/or facility-operated building management systems, such as a Supervisory Control and Data Acquisition (SCADA) system. 
         [0013]    According to one aspect of this disclosure, a method is provided for recovering waste heat in a building having a location for recovery of waste heat that is only easily accessible through at least one pedestrian door. The method comprises the steps of:
       assembling at least two dual heat pump modules, a source water pump, a heat transfer fluid pump, and a controller to a frame;   connecting piping between the heat pump modules, the source water pump, and the heat transfer fluid pump to form an assembled modular unit;   transporting the assembled modular unit through the at least one of the pedestrian door into the building;   connecting the source water pump to a stream of a source fluid;   connecting the heat transfer fluid pump to a heat transfer fluid circuit that circulates a heat transfer fluid; and   connecting the controller to a power source.       
 
         [0020]    According to other aspects of this disclosure, the method may further comprise balancing the flow of the source fluid with a set of inlet balancing valves and a set of outlet balancing valves. The balancing step may be performed automatically with automatic flow regulator/valves. 
         [0021]    According to another aspect of this disclosure, the method may further comprise controlling the operation of the heat pump modules, the source water pump, the heat transfer fluid pump based upon a temperature of the source fluid and a temperature of the heat transfer fluid. 
         [0022]    The method may also further comprise controlling the operation of the heat pump modules, the source water pump, and the heat transfer fluid pump based upon the flow rate in the heat transfer fluid circuit. 
         [0023]    To provide scalability, two or more assembled modular units may be provided in combination with the first assembled modular unit by repeating the steps for providing the first assembled modular unit. 
         [0024]    According to another aspect of this disclosure, a modular heat recovery system is disclosed that comprises a frame and at least two dual heat pump modules assembled to the frame. A source water pump is connected by piping to the dual heat pump modules. A heat transfer fluid pump is connected by piping to the dual heat pump modules. A controller is electrically connected to the dual heat pump modules, the source water pump and the heat transfer fluid pump to form a modular unit that is adapted to be transported through a pedestrian door. 
         [0025]    According to other aspects of this disclosure, the modular heat recovery system is adapted to be transported through a pedestrian door having a width of less than one meter and a height of less than three meters. 
         [0026]    The modular heat recovery system may further comprise a set of inlet balancing valves connected to the source water pump and the heat pump modules and a set of outlet balancing valves connected to the source water pump and the heat pump modules. The inlet balancing valves and the outlet balancing valves may be automatic flow regulator/valves. 
         [0027]    The controller controls the operation of the heat pump modules, the source water pump, the heat transfer fluid pump based upon a temperature of the source fluid and a temperature of the heat transfer fluid. As an alternative or in combination, the controller may control the operation of the heat pump modules, the source water pump, the heat transfer fluid pump based upon a flow rate in the heat transfer fluid circuit. 
         [0028]    The modular heat recovery system may be scaled by providing two or more frames with one or two heat pump modules, a source water pump, a heat transfer fluid pump and a controller for controlling the heat pump modules, the source water pump and the heat transfer fluid pump to form two or more assembled modular units that are each separately adapted to be transported through the pedestrian door. 
         [0029]    The above aspects of this disclosure and other aspects are described below with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  is a perspective view of a modular heat recovery system made according to one embodiment of this disclosure. 
           [0031]      FIG. 2  is a simplified schematic view of the fluid and electrical control circuit of the modular heat recovery system illustrated in  FIG. 1 . 
           [0032]      FIG. 3  is a detailed schematic of one embodiment of the heat recovery system of this disclosure. 
           [0033]      FIGS. 4A and 4B  are perspective views of the front and rear sides, respectively, of an alternative modular dual heat recovery system made according to a second embodiment of this disclosure. 
           [0034]      FIG. 5  is an exploded perspective view of the modular dual heat recovery system of  FIG. 4 . 
           [0035]      FIG. 6  is a perspective view of three modular dual heat recovery systems connected together as an integrated scalable system. 
           [0036]      FIG. 7  is a detailed schematic of one embodiment of the heat recovery system of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    The illustrated embodiments are disclosed with reference to the drawings. However, it is to be understood that the disclosed embodiments are intended to be merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but as a representative basis for teaching one skilled in the art how to practice the disclosed concepts. 
         [0038]    Referring to  FIGS. 1, 4A and 4B , a modular heat recovery system is generally indicated by reference numeral  10  (in  FIG. 1 ) or  120  (in  FIGS. 4A and 4B ) that are capable of recovering heat from a source of flowing water, air or other fluid. For example, effluent from a waste water treatment facility may be the source of water that heat may be recovered from to heat or cool a building. Other sources of flowing fluids may be used with the modular heat recovery system  10  such as irrigation systems, geo-thermal systems, and the like. A principal focus of the system is that it is comprised of small preassembled modules that can be installed as modular units in existing buildings that have conventional sized access doors. The system is scalable to fulfill the HVAC requirements of a wide range of buildings by adding additional heat pump modules and selecting fluid pumps accordingly. 
         [0039]    The heat pump modules  12  are high efficiency heat pumps that include a compressor (a dual scroll compressor), heat exchanger, condenser and expansion valve (not shown in  FIG. 1 ). A dual pump module  14  (shown in  FIG. 1 ) is provided that has a source loop pump that pumps the source fluid through the heat pump modules that include a pair of parallel heat pumps. In the embodiment of  FIGS. 4A and 4B , a source water pump  14   a  is illustrated that pumps the source fluid through the heat pump modules and a heat transfer fluid pump  14   b  is illustrated that pumps the Heat Transfer Fluid (“HTF”) through the heat pump modules. The heat pump modules  12  are connected in parallel for independent operation. The dual pump module  14 , as shown in  FIG. 1 , includes a load loop pump that pumps the HTF through the heat pump modules in series to the heating and/or dehumidifier/air conditioning points of use. The heat transfer fluid pump  14   b  pumps HTF through the heat pump modules in series to the heating and/or dehumidifier/air conditioning systems. 
         [0040]    A Programmable Logic Control (PLC) module  16  is provided that is connected to a power supply  18  that may be a 208-230/460 volt, 60 cycle, 3 phase power source from the electrical power grid. The system may also be adapted to be powered by other power supplies. The PLC module  16  controls the operation of the heat pump modules  12  and the dual pump module  14  (or source water pump  14   a  and heat transfer fluid pump  14   b ). The PLC module  16  also provides control logic to the heat pump modules  12  and the dual pump module  14  (or source water pump  14   a  and heat transfer fluid pump  14   b ). 
         [0041]    Referring to  FIG. 1 , standardized cabinets having over all dimensions less than or equal to a standard doorway, e.g. 34½ W×78½ H×96 L, are provided to house the heat pump modules  12 , dual pump module  14  and PLC module  16 . The cabinets may have removable service panels  22  to facilitate inspection and repair of the system. A Human Machine Interface (HMI)  22  is provided on the PLC module  16  to facilitate monitoring and adjusting the modular heat recovery system  10 . The modules may be assembled on a platform  26  or may be attached to a frame  27 , as shown in  FIGS. 4A and 4B . 
         [0042]    The heat pump modules  12  and dual pump module  14  (or source water pump  14   a ) are connected by source supply piping  30  and source return piping  32  in series with standardized couplings to facilitate installation and expansion of the system  10 . Likewise, the heat pump modules  12  and dual pump module  14  (or heat transfer fluid pump  14   b ) are connected by heat transfer fluid piping  30  in series with standardized couplings to facilitate installation and expansion of the system  10 . 
         [0043]    Power and control wiring conduit  38  is also shown in  FIG. 1  that is connected to the heat pump modules  12  and the PLC system  16 . The PLC system  16  and the dual pump modules  14  are also connected by wiring that are also in a conduit that is are not visible in  FIG. 1 . The power and control conduit  38  connects the heat pump modules  12  in series and with the PLC system  16  with standardized couplings to facilitate installation and expansion of the system  10 . 
         [0044]    Referring to  FIG. 2 , two (2) dual heat pump modules  12 , the dual pump module  14  and PLC system  16  are illustrated in a schematic diagram  40 . The PLC system  16  provides power from the power supply  18  to the system  10  that is distributed to the heat pump modules  12  and the dual pump module  14  through the power and control conduit  38 . 
         [0045]    The source supply piping  30  feeds the dual pump module  14  with a fluid that is pumped to the heat pump modules  12 . In a heating system, heat is transferred from the source fluid in the heat pump modules to the HTF in the load loop return piping  36  that is also pumped in parallel by the dual pump module. The fluid is directed to the source return piping  32  back to the source or to a drain after passing through the heat pump modules  12 . 
         [0046]    An expansion tank  40  is provided to maintaining consistent heat transfer fluid pressure within the operating system. The heated HTF is then directed through the load loop supply piping  34  to heat the building. 
         [0047]    The heat pump modules  12  each include two compressors, two heat exchangers, two condensers and two expansion valves that are graphically represented by block  42  in  FIG. 2 . 
         [0048]    Referring to  FIG. 3 , a schematic of the piping, power distribution and data feedback for the modular heat recovery system  10  is provided. The heat pump module  12  corresponding to the block  42  in  FIG. 2  is shown with the programmable logic control system  16  that is powered by the power supply  18 . The Human Machine Interface (HMI)  24  is used to control the PLC system  16  and modular heat recovery system  10 . 
         [0049]    Source influent piping  30  supplies water or other source fluid to a source pump  48 . The source pump  48  pumps the fluid through a check valve into source distribution piping  50  and into the heat pump module  12 . The fluid in the source distribution piping  50  is directed through a first heat pump branch  52  through an isolation valve to a first heat pump  54 . Part of the source fluid is directed to the second heat pump branch  56  that supplies the source fluid to the second heat pump  58 . 
         [0050]    The first heat pump  54  and second heat pump  58  are connected in parallel to each other and are both included as part of the heat pump module  12 . In this case, the first heat pump module corresponds to block  42  in  FIG. 2 . If, as anticipated, several heat pump modules  12  are included in the modular heat recovery system  10 , as shown in  FIG. 2 , the other heat pump modules  12  are connected through additional isolation valves by a serially connected heat pump piping  60 . The additional heat pump modules  12  are added as heating or cooling requirements of a building increase. 
         [0051]    A first source return piping branch  62  returns the source fluid from the first heat pump  54  through an isolation valve and a balancing valve to source return piping  64 . The balancing valve provides flow control at each heat pump. Similarly, a second source control piping branch  66  provides for the return of source fluid from the second heat pump  58  through an isolation valve and a balancing valve to the source return piping  64 . 
         [0052]    HTF pump  70  pumps the heat transfer fluid through HTF distribution pump piping  72  including isolation valves and a balancing valve to the point of use  76 , or load that transfers heat to the building or cools and dehumidifies the building depending upon whether the system is a heating or cooling system. The HTF returns from the point of use at  78  after having transferred heat to or from the building. 
         [0053]    The HTF is directed through an isolation valve into heat transfer fluid return distribution piping  80 . The HTF flowing through the heat transfer fluid return distribution piping  80  is directed through an isolation valve to a first heat pump branch  82  and through an isolation valve to a second heat pump branch  84  that provide heat transfer fluid to the first heat pump  54  and second heat pump  58 , respectively. Serially connected heat pump piping  86  directs the HTF through an isolation valve to subsequent heat pump modules  12  that are provided as part of the modular heat recovery system  10 . A first HTF supply piping branch  88  and a second HTF supply piping branch  90  direct the HTF through separate isolation valves and balancing valves into HTF distribution piping  92 . 
         [0054]    The HTF distribution piping  92  supplies the heat transfer fluid to an expansion tank branch  98 . The expansion tank branch  98  provides heat transfer fluid to an expansion tank  40  that compensates for variation heat transfer fluid pressure and maintains consistent heat transfer fluid pressure. The expansion tank branch  98  includes an expansion tank branch  98  that provides the heat transfer fluid through an isolation valve to the expansion tank  40 . The expansion tank branch  98  also includes a HTF pump branch  100  that provides the heat transfer fluid to the heat transfer pump  70 . 
         [0055]    Heat pump sensor power supply wiring  102  provides power to sensors that are used to monitor the operation of the modular heat recovery system  10 . Distribution sensor power supply wiring  104  provides power to sensors in the source and HTF fluid distribution portions of the system. Pressure sensors  106  (P), temperature sensors  108  (T) and flow sensors  110  (F) monitor the pressure, temperature and flow of the source fluid and HTF throughout the heat recovery system  10 . The sensors provide pressure, temperature and flow data through wiring  112  (or by wireless communication) to the PLC system  16 . 
         [0056]    The PLC system  16  provides power through a source pump power supply  114  to the source pump  48 . A HTF pump power supply  116  similarly provides power to the HTF pump  70 . The power supplied to the source pump  48  and HTF pump  70  is controlled based upon the data received from the pressure sensors  106 , temperature sensors  108  and flow sensors  110 . 
         [0057]    Operation of the instrumentation and PLC system for the modular heat recovery system  10  is described below. 
         [0058]    The heat recovery system  10  includes heat pump modules  12  that each includes two heat pumps  54  and  58 . The PLC control system  16  determines the sequence for initiating the system operation. The heat pumps are staged based upon the return temperature of the load loop  34 . As the load loop  34  temperature decreases (in a heating system or mode), the heat pumps  54  and  58  are started and the HTF in the load loop return  36  is heated. 
         [0059]    The PLC system  16  may be configured to sequence operation of the heat pumps  54  and  58 . The PLC system  16  can automatically alternate operation of the two heat pumps within the heat pump module  12 . The PLC system  16  determines which heat pump is turned on first and which is turned off first and also provides the ability to remove a heat pump from service. In the event the source influent supply is interrupted, or insufficient, the PLC system  16  may be programmed to shut down the heat pumps until adequate influent supply is available. 
         [0060]    Enabling the modular heat recovery system  10  is a manual operation controlled by building maintenance personnel through the human machine interface (HMI)  24 . For example, in a heating system, the modular heat recovery system  10  may be enabled in the fall and disabled in the spring based upon outside air temperature and building HVAC requirements. If the heat recovery system  10  is configured to provide both heating and cooling, the system may be automatically controlled to provide the heating and cooling source for the HVAC system. 
         [0061]    When the heat recovery system  10  is enabled, the source loop pump  48  and load loop pump  70  are started and the selected heat pump module  12  is started to begin heating or cooling the HTF. Additional heat pumps may be staged based upon increasing or decreasing load loop return temperatures. As the load loop return  36  temperatures vary, additional heat pump modules  12  may be started depending upon the increasing or decreasing load loop return  36  temperature. The temperature value set points for staging the heat pump modules  12  to turn on or turn off are user definable and may be entered into the PLC system  16  by the HMI  24 . 
         [0062]    The heat recovery system  10  reduces energy costs while optimizing performance of the HVAC system of a building. The heat pump modules  12  remove heat or add heat to the source influent to efficiently transfer heat. Heat transfer fluid is used to transfer heat to the point of use, or load, heat exchangers. Waste heat is thus repurposed for use in heating a building and reduces or eliminates the need to use gas or electricity to heat or cool a building. 
         [0063]    The source supply fluid may include sediment and there is no need to filter or otherwise act upon the source fluid as it flows through the system. The modular heat recovery system  10  may be used with a waste water treatment facility or any other facility where a reliable source of flowing water or other fluid having the appropriate temperature and flow characteristics is available. 
         [0064]    In general, the system is expected to improve the reliability of HVAC systems because there is no need for make-up air unit burners. In addition, the heat recovery system allows bypassing individual heat pump modules during system maintenance or repair operations so that system operation does not need to be interrupted. 
         [0065]    Referring to  FIG. 5 , the component parts of the alternative embodiment of the modular heat recovery system  120  are illustrated. The frame  27  includes a base  122  to which supports  124  are attached. The components of the modular heat recovery system  120  are secured to the base  122  and supports  124 . The dimensions of the base  122 , supports  124  and components attached thereto are minimized to permit the modular heat recovery system  120  to be transported through a conventional door. As used herein, the term conventional door refers to a pedestrian door having a width of less than one meter and a height of less than three meters. 
         [0066]    The heat pump modules  12  are attached to the opposite ends of the base  122  and are also secured to the supports  124 . Source water piping  126  is connected to the source fluid, such as a waste water stream, and provides the source water or fluid to the two heat pump modules  12  that are assembled to the base  122 . Source water pump  14 A provides the source water under pressure to the source water piping  126 . A ball valve  128  is provided to allow the source water to be selectively turned on and off for service operations. A pair of pressure gauges  130  are provided to monitor the pressure of the source water provided to the heat pump modules  12 . 
         [0067]    Heat transfer fluid piping  132  is connected to the heat transfer fluid pump  14 B. The heat transfer fluid piping  132  provides the heat transfer fluid to the heat pump modules  12 . A ball valve  134  is provided in the heat transfer fluid piping  132  to control the flow of heat transfer fluid and permit selective interruption of the flow of heat transfer fluid. Pressure gauges  136  monitor the pressure within two branches of the heat transfer fluid piping  132  that are provided to the heat pump modules  12 . A drain valve  138  is provided to permit the heat transfer fluid to be drained during service operations. 
         [0068]    Balancing valves  140  are provided for balancing the heat transfer fluid within the system. A pair of pressure gauges  142  are used to monitor the pressure within the heat transfer fluid as it flows through the balancing valve piping  144 . A ball valve  146  allows the flow of heat transfer fluid through the balancing valve piping  144  to be turned on and off. 
         [0069]    Balancing valves  148  are also provided for the source fluid that facilitate balancing the flow of fluid through the modular heat recovery system  120 . The balancing valves  148  are monitored by pressure gauges  150  that are assembled to the balancing valve piping  152 . A ball valve  154  is provided to permit the flow of source fluid through the balancing valve piping  152  to be turned on and off. A drain  156  is provided to permit the source fluid to be drained from the balancing valve piping  152  during service operations. 
         [0070]    A rack  160  is assembled to the base  122  and supports  124  of the frame  27 . The PLC system  16  for each heat pump module  12  is assembled to the rack  160 . The rack is adapted to support a pair of 30 amp safety switches  152  and 60 amp safety switches  164 . The safety switches  162  and  164  and PLC system  16  are connected by wiring in conduits  166 . 
         [0071]    U-bolt  170  type brackets are provided to secure the source influent piping  30 , source effluent piping  32 , load loop supply piping  34  and load loop return piping  36  to the supports  124 . The length of the piping  30 ,  32 ,  34  and  36  is limited to approximately the width of the modular heat recovery system  10  so that the piping and all the other components of the modular heat recovery system  10  can be preassembled at a remote location and moved into a building to be serviced by the modular heat recovery system. The size of the module is limited to be able to fit within pedestrian doors, as previously indicated, so that the only assembly necessary within the building is the connection of multiple modules and connections to the source fluid and heat transfer/load circuits. 
         [0072]    Temperature sensors  172  are provided in the source effluent piping  32  and the load loop supply piping  34 . A flow meter  174  is provided in the heat transfer fluid return  36 . The flow meter  174  monitors the rate of flow of the heat transfer fluid through the load loop return  36 . 
         [0073]    Referring to  FIG. 6 , HTF piping connector segments  176  are connected between adjacent modular heat recovery systems indicated by  10   a ,  10   b  and  10   c  in  FIG. 6 . The HTF connector piping segments may be of standardized length to facilitate assembly of multiple modules and also assure adequate spacing between modules for servicing. Similarly, source fluid piping connector segments  180  are provided to connect adjacent modular heat recovery systems  10   a ,  10   b , and  10   c . Caps  182  are provided on one end of each of the load and source piping connections. 
         [0074]    Referring to  FIG. 7 , a schematic of the modular heat recovery system  120  is provided. Source influent piping  30  supplies water or another source fluid to a source pump  48 . The source pump  48  pumps fluid through source distribution piping  50  and into the two heat pump modules  12  through a first heat pump branch  52  and a second heat pump branch  56  to the second heat pump  58 . 
         [0075]    The first heat pump  54  and second heat pump  58  are connected in parallel to each other and are both included as part of one of the heat pump modules  12 . If more than one modular heat recovery systems is required, additional heat pump modules  12  are connected through isolation valves by serially connected heat pump piping. Additional heat pump modules  12  are added as heating or cooling requirements of a building change. 
         [0076]    A first source return piping branch  64  returns the source fluid from the heat pump modules  54  and  58  through ball valves  128  and automatic balancing valves  148 . The balancing valves  148  provide flow control for each heat pump. The source water from the source return piping branch  64  is provided to the heat pump piping  60  for return to the source fluid stream. 
         [0077]    Heat transfer fluid pump  70  pumps the heat transfer fluid through the HTF distribution piping  72  and into the first heat pump branch  82  and through an isolation valve to a second heat pump branch  84  to provide heat transfer fluid to the first heat pump  54  and second heat pump  58 , respectively. A first heat transfer supply piping branch  88  and second HTF supply piping branch  90  supply HTF to distribution piping  92  and heat pumps  54  and  58  prior to being supplied to the distribution branches  88  and  90 . The HTF is supplied through the HTF load supply line  74  to a pressure tank  40  that may also be referred to as an expansion tank. The HTF flowing from the pressure tank  40  is provided to HTF distribution pumping to the point of use  76 . The point of use  76  refers to the heating or air conditioning units in a building that are used to heat and cool the building. After supplying the HTF to the building, HTF is returned through return piping from the point of use at  78 . Flow meter  110  measures the flow of the returning HTF. The HTF is then returned through HTF return distribution piping  80  to the HTF pump  70 . 
         [0078]    The HTF pump  70  may be controlled by a variable frequency drive  186 . The variable frequency drive  186  controls the displacement of the HTF pumps  70 . A HTF pump current sensor  188  monitors the variable frequency drive  186  and a HTF pump control relay  190  is provided to control the operation of the variable frequency drive  186 . 
         [0079]    The source fluid pump  48  is monitored by a source fluid pump current sensor  192  that cooperates and provides source fluid pump current data that is used to control a source fluid pump control relay  194 . The source fluid pump control relay  194  controls the operation of the source fluid pump  48 . 
         [0080]    The temperature of the source fluid is measured by temperature sensor  108 -T 1 . The returning HTF is also sensed by temperature sensor  108 -T 2  and the pressure of the returning HTF is sensed by a pressure sensor  106 -P 2 . Temperature sensor  108 -T 3  measures the temperature of the source fluid effluent and provides this information to the control panel  16 . Temperature sensor  108 -T 4  measures the source water supply to the source water return temperature and provides this temperature information to the control panel  16 . 
         [0081]    Thirty amp safety switches  162  and 60 amp safety switches  164  provide a safety disconnect for the pumps and the heat exchange modules  54 - 58 . 
         [0082]    The embodiments described above are specific examples that do not describe all possible forms of the disclosure. The features of the illustrated embodiments may be combined to form further embodiments of the disclosed concepts. The words used in the specification are words of description rather than limitation. The scope of the following claims is broader than the specifically disclosed embodiments and also includes modifications of the illustrated embodiments.