Patent Publication Number: US-2020277760-A1

Title: System and method of hot water recirculation using a bi-directional cold-water supply line

Description:
BACKGROUND 
     The need for heated fluids, and heated water, has long been recognized. Conventionally, water has been heated by water heaters containing heating elements. These water heaters are conventionally heated either electrically or with gas burners, where the heated water may be stored in a tank or reservoir. Additionally, such water heaters may be tankless, circulating hot water into a plumbing system without storing the water in a tank or reservoir. Water heaters are often used in private and commercial plumbing networks. Plumbing networks often require water to be continuously circulated into a heater to maintain a desired water temperature in hot-water supply lines. 
     Many modern businesses, such as Quick Service Restaurants (QSRs) for example, use existing water plumbing networks that are not particularly configured for hot-water recirculation. As such, these water plumbing networks often do not have a dedicated hot-water recirculation line to reheat lukewarm water that may sit in the plumbing network. But, many businesses use modern appliances and plumbing fixtures, which may require hot water at a set temperature. This set temperature may be necessary to meet safety requirements. For example, some businesses use automatic dish washers that use heated water to disinfect dirty dishes. Plumbing fixtures in such applications often require a small amount of water to operate, while drawing water from an extensive plumbing network. 
     As water sits in an extensive plumbing network, the water cools due to heat loss in the network&#39;s pipes, if the water is not recirculated. A plumbing network may contain a large amount of water, such as five gallons for example, between a water heater and a plumbing fixture. In some applications, a plumbing fixture may draw one to one and a half gallons of water in an operational cycle, causing it to only draw lukewarm water. As such, there is a need for a hot-water recirculation system that can operate in a water circulation network that does not contain a dedicated hot-water recirculation line. 
     SUMMARY 
     A first aspect of the disclosure provides a recirculation pump system. The recirculation pump system comprises an inlet adapted to be fluidically connected to a hot-water supply line. The recirculation pump system comprises an outlet adapted to be fluidically connected to a cold-water supply line. The recirculation pump system comprises a temperature sensor configured to sense a temperature at the inlet. The recirculation pump system comprises a water pump configured to pump water from the inlet to the outlet upon the temperature sensor detecting a lower threshold temperature. The recirculation system comprises a check valve configured to prevent water flow from the outlet to the inlet. 
     In some implementations of the first aspect of the disclosure, the water pump is further configured to stop pumping water from the inlet to the outlet upon the temperature sensor detecting an upper threshold temperature. 
     In some implementations of the first aspect of the disclosure, the upper threshold temperature is adjustable and may be set at 120 degrees Fahrenheit. 
     In some implementations of the first aspect of the disclosure, the lower threshold temperature is adjustable and may be set at 110 degrees Fahrenheit. 
     In some implementations of the first aspect of the disclosure, the check valve is configured to be positioned between the water pump and the outlet. 
     A second aspect of the disclosure describes a water recirculation system comprising a heat engine, having a cold-water inlet and a hot-water outlet. The water recirculation system comprises a hot-water supply line adapted to be fluidically connected to the hot-water outlet. The hot water recirculation system comprises an inlet adapted to be fluidically connected to the hot-water supply line. The hot water recirculation system comprises an outlet adapted to be fluidically connected to a cold-water supply line. The cold-water supply line is adapted to be fluidically connected to the cold-water inlet. The water recirculation system comprises a temperature sensor configured to sense a temperature in the hot-water supply line. The water recirculation system comprises a water pump configured to pump water from the hot-water supply line to the cold-water supply line upon the temperature sensor detecting a lower threshold temperature. The water recirculation system comprises a check valve configured to prevent water flow from the cold-water supply line to the water pump. 
     In some implementations of the second aspect of the disclosure, the water pump is further configured to stop pumping water in from the inlet to the outlet upon the temperature sensor detecting an upper threshold temperature. 
     In some implementations of the second aspect of the disclosure, the upper threshold temperature is adjustable and may be set at 120 degrees Fahrenheit. 
     In some implementations of the second aspect of the disclosure, the lower threshold temperature is adjustable and may be set at 110 degrees Fahrenheit. 
     In some implementations of the second aspect of the disclosure, the water pump is configured to circulate water from the hot-water supply line through the cold-water supply line to the cold-water inlet of the heat engine. 
     In some implementations of the second aspect of the disclosure, at least one or more plumbing fixtures are fluidically connected to the hot-water supply line and the cold-water supply line. 
     In some implementations of the second aspect of the disclosure, the water pump is coupled across the hot-water supply line, and the cold-water supply line at a furthest plumbing fixture from the hot-water outlet. 
     In some implementations of the second aspect of the disclosure, one or more plumbing fixtures are fluidically connected between the furthest plumbing fixture and the heat engine. 
     In some implementations of the second aspect of the disclosure, one or more of the plumbing fixtures are configured to operate on a cycle that draws an amount of water from the hot-water supply line that is less than an amount of water in the hot-water supply line between the hot-water outlet and the one or more of the plumbing fixtures. 
     In some implementations of the second aspect of the disclosure, the heat engine is a tankless water heater. 
     A third aspect of the disclosure describes a method of recirculating hot water comprising activating a water pump in a water recirculation system. The method of recirculating hot water comprises circulating, by the water pump, water from a hot-water supply line through a cold-water supply line to a cold-water inlet of a heat engine inlet. The method of recirculating water comprises circulating, by the water pump, water from a hot-water outlet of the heat engine to the hot-water supply line. The method of recirculating water comprises measuring a temperature of the water in the hot-water supply line. The method of recirculating water comprises deactivating the water pump when the water reaches an upper threshold temperature. 
     In some implementations of the third aspect of the disclosure, the method of recirculating water further comprises reactivating the water pump when the water in the hot-water supply line falls below a lower threshold temperature. 
     In some implementations of the third aspect of the disclosure, the upper threshold temperature is adjustable and may be set at 120 degrees Fahrenheit. 
     In some implementations of the third aspect of the disclosure, the lower threshold temperature is adjustable and may be set at 110 degrees Fahrenheit. 
     In some implementations of the third aspect of the disclosure, the heat engine is a tankless water heater. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. 
         FIG. 1  illustrates a recirculation pump system diagram, showing individual components. 
         FIG. 2  illustrates a water recirculation system diagram. 
         FIG. 3  illustrates a water recirculation system flow chart. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood at the outset that although illustrative implementations of one or more embodiments are illustrated below, the disclosed systems and methods may be implemented using any number of techniques, whether currently known or in existence. Like numbers represent like parts throughout the various figures, the description of which is not repeated for each figure. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, but may be modified within the scope of the appended claims along with their full scope of equivalents. Use of the phrase “and/or” indicates that any one or any combination of a list of options can be used. For example, “A, B, and/or C” means “A”, or “B”, or “C”, or “A and B”, or “A and C”, or “B and C”, or “A and B and C”. 
     A recirculation pump system that comprises a temperature sensor, a water pump and a check valve provides the ability to recirculate water from a hot-water heater outlet, back into a water heater inlet through a cold-water supply line. Such hot-water bypass systems are particularly beneficial where a plumbing fixture requires hot water at a set temperature, such as an automatic dishwasher for example, is installed in an existing plumbing network. 
     In such systems, the existing plumbing network often does not contain a dedicated hot-water recirculation return line. A temperature sensor may connect to a hot-water supply line that contains heated water at a given time. The temperature sensor may sense when water temperature falls below a certain preset temperature. The temperature sensor may activate a water pump that is fluidically networked to circulate water up a cold-water supply line to a cold-water inlet on a water heater. A water circulation system may utilize the water pump at a furthest fixture from the water heater. When the water pump circulates the water, the water heater may activate and heat the circulating water to replenish the hot-water supply line with hot water at a heater set point temperature. 
     The temperature sensor may also sense an upper threshold water temperature and deactivate the water pump. This ensures that water hotter than the upper threshold water temperature is not circulated through the cold-water supply line in the water circulation system. When the water cools again to the preset temperature, due to heat loss in the plumbing network, the temperature sensor may activate the water pump again. 
     The preset temperature and the upper threshold temperature may be adjusted by a user. This allows a user to manage the temperature of hot-water entering the cold-water supply line and plumbing fixtures. As such, the adjustable preset temperature and the upper threshold temperature allows the hot-water recirculation system to provide hot water to fixtures at a desired temperature while preventing excess hot water from overwhelming the cold-water supply line. The temperature sensor further allows the hot-water recirculation system to maximize energy efficiency by only operating when necessary. The recirculation pump system may provide a minimally invasive way to install a hot-water recirculation system in a plumbing network that does into contain a hot-water recirculation line. This is important in applications where modern appliances may be installed in previously existing plumbing networks, which are not designed to otherwise accommodate such modern appliances and their heating requirements. 
       FIG. 1  illustrates a recirculation pump system  100 , having a hot-water line  102 . The hot-water line  102  being fluidically connected to a water pump  104  at a water pump inlet  104   a.  The water pump  104  also having an outlet  104   b.  The water pump outlet  104   b  may be fluidically connected to a check valve  106 . The check valve  106  may be a spring check valve, such as a ¾-inch spring check valve for example. The check valve  106  may be configured to limit the flow of water through the check valve  106  to a single direction—a direction from the hot-water line  102  to a cold-water supply line  108 , as shown. The check valve  106  may have an inlet  106   a  and an outlet  106   b  wherein the check valve inlet  106   a  is fluidically connected to the water pump outlet  104   b  and the check valve outlet  106   b  is fluidically connected to the cold-water supply line  108 . The cold-water supply line  108  may be configured to be fluidically connected to a cold-water source (shown in  FIG. 2 ) and a heat engine cold-water inlet (shown in  FIG. 2 ). In embodiments, the check valve  106  may be located between the water pump,  110  and the cold-water supply line  108  to restrict fluid flow to circulate out of and away from the water pump outlet  104   b,  such that no cold water may flow into the water pump outlet  104   b.    
     The recirculation pump system  100  may be configured such that the recirculation pump system  100  is controlled by a temperature sensor  110 . In embodiments, the temperature sensor  110  may be disposed about the hot-water line  102 . The temperature sensor  110  may comprise a sensing element, such as a copper sensing element, that may sense the temperature of the hot-water line  102  through heat transfer through the hot water line  102 . In some implementations, the temperature sensor  110  may also sense the water temperature by using a temperature probe to contact the water directly. Other variations of the temperature sensor  110  are contemplated by this disclosure. 
     The temperature sensor  110  may be programmable and may be electrically connected to the water pump  104 , such that the water pump  104  may be activated when the temperature sensor  110  senses that the water has reached a lower threshold temperature. In embodiments, the lower threshold temperature of the water may be  110  degrees Fahrenheit. The temperature sensor  110  may also be configured to deactivate the water pump  104  when the temperature sensor  110  senses an upper threshold temperature. In embodiments, the upper threshold temperature may be  120  degrees Fahrenheit or greater. The temperature sensor may be a HONEYWELL AQUASTAT L6006C, for example. The upper threshold temperature and/or the lower threshold temperature may be programmatically adjusted on the temperature sensor  110  to ensure that hot water at a desired temperature is provided to fixtures at a desired temperature while preventing excess hot water from overwhelming the cold-water supply line. 
       FIG. 2  illustrates a water recirculation system  200  which is configured to integrate the recirculation pump system  100  (shown in  FIG. 1 ) into a plumbing network. The recirculation pump system  100  has an inlet point  202  and an outlet point  204 . The recirculation pump system inlet point  202  is fluidically connected to the hot-water line  102  and the recirculation pump system outlet point  204  is fluidically connected to the cold-water supply line  108 . The cold-water supply line  108  is fluidically connected to at least one heat engine  206 , at a water heater cold-water inlet  208 . The at least one heat engine  206  may also have a heat engine hot-water outlet  210 . The heat engine hot-water outlet  210  being fluidically connected to the hot-water line  102 . The hot-water line  102  and the cold-water supply line  108  may each also be fluidically connected to at least one plumbing fixture  212   a - f . The hot-water line  102  may route hot water from the at least one water heater  206  to the at least one plumbing fixture  212   a - f . The cold-water supply line  108  may also route cold water to the at least one plumbing fixture  212   a - f . The cold-water supply line  108  may also be fluidically connected to a cold-water source  214 , such as a municipal water supply, that may provide cold water to the at least one plumbing fixture  212   a - f  and the heat engine cold-water inlet  208 . 
     The recirculation pump system  100  may be disposed within the water recirculation system  200 . When the temperature sensor  110  senses a water temperature in the hot-water line  102  that is below the lower threshold temperature, the water pump  104  may circulate water from the hot-water line  102  into the cold-water supply line  108  and through the heat engine  204 . As such, the recirculated hot water may be fluidically connected to the cold-water source and the at least one heat engine  204 . Therefore, the water recirculation system  200  uses the cold-water supply line  108  as a recirculation path for the hot water as well as a cold-water supply path. In embodiments, the at least one heat engine  204  may be a tankless water heater, or multiple tankless water heaters, each fluidically connected to the hot-water line  102  and the cold-water supply line  108 . The at least one heat engine  204  may also be a tank water heater, that heats water and stores it in a hot-water storage tank (not shown). 
       FIG. 3  illustrates a flow diagram showing a process  300  for recirculating hot water through a water recirculation system with the water pump  104 . At  302 , the water pump  104  may be activated remotely or locally. A user may activate the water pump  104  at the time of desired operation, or a user may set a timer that activates the water pump  104  automatically at a set time. The water pump  104  may also be electronically connected to a temperature sensor  110 , which may activate the water pump when it senses a certain temperature, or range of temperatures. In some embodiments the temperature sensor  110  may activate the water pump  104  upon sensing a lower threshold temperature. The lower threshold temperature is an adjustable temperature that may be a predetermined temperature set by a user or otherwise programmed into the temperature sensor  110 . 
     The water pump  104  may circulate the water from the hot-water line  102  through the cold-water supply line  108  and into the at least one heat engine  204 . The at least one heat engine  204  may heat the water circulating therethrough  304 . The at least one heat engine  204  may be a water heater. In embodiments, the at least one heat engine  204  may be a tankless water heater. The at least one heat engine  204  may transfer heat to the water that is circulating through it by conduction, or some other form of heat transfer such as convection or radiation. The hot water may then be circulated out of the at least one heat engine  204  into the hot-water line  102  at a set point temperature. 
     A temperature sensor  110  may sense the temperature of the hot water  306 , by using a sensing element to take the temperature of a surface of the hot-water line  102 . In embodiments, the temperature sensor may also take the temperature of the water in the hot-water line  102  directly, using a probe disposed within hot-water line  102 . In embodiments, the temperature sensor may deactivate the water pump  104  when the temperature sensor  110  senses an upper threshold temperature  306 . The upper threshold temperature is an adjustable temperature that may be a predetermined temperature set by a user or otherwise programmed into the temperature sensor  110 . The temperature sensor  110  may be electronically connected to the water pump  104 , such that the temperature sensor  110  signals the water pump  104  to deactivate when it senses the upper threshold temperature. 
     The temperature sensor  110  may sense a lower threshold temperature  308 . In embodiments the temperature sensor  110  may activate the water pump  104  upon sensing a lower threshold temperature. The temperature sensor  110  may reactivate the water pump as shown at  302 . The water recirculation system  200  may continue this cycle as long as a user intends to maintain hot water in the water recirculation system  200 . 
     While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted or not implemented. 
     Also, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component, whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.