System and method for controlling a pump in a recirculating hot water system

1. A recirculating hot water system comprising:

a storage tank for storing heated water;

a recirculation conduit comprising:

a supply conduit for supplying the heated water to users via a plurality of outlets having a first outlet and a last outlet; and

a return conduit for returning an unused portion of the heated water to the storage tank;

a pump for circulating the heated water, the pump disposed along the return conduit;

a temperature sensor, disposed along the recirculation conduit, for generating a temperature signal indicative of a temperature of the heated water; and

a control unit, coupled to the pump, for changing a speed of the pump based on the temperature signal, wherein the control unit is configured to:

store a first temperature value of the temperature signal at a first time;

increase the speed of the pump to raise the temperature of the heated water to a preselected second temperature value;

measure a time elapsed as the measured temperature increases from the first temperature to the preselected second temperature; and

operate the pump for a period of time based at least in part on the time elapsed.

2. The recirculating hot water heating system of claim 1 , wherein the temperature sensor is disposed along the return conduit.

3. The recirculating hot water heating system of claim 1 , wherein the temperature sensor is disposed along the return conduit proximate the pump.

4. The recirculating hot water heating system of claim 1 , wherein the temperature sensor is disposed proximate the last outlet.

5. The recirculating hot water heating system of claim 1 , wherein the temperature sensor communicates with the control unit using wireless communication.

6. The recirculating hot water heating system of claim 1 , wherein the temperature sensor communicates with the control unit using a wired connection.

7. A recirculating hot water system comprising:

a storage tank for storing heated water;

a recirculation conduit comprising:

a supply conduit for supplying the heated water to users via a plurality of outlets having a first outlet and a last outlet; and

a return conduit for returning an unused portion of the heated water to the storage tank;

a pump for circulating the heated water, the pump disposed along the return conduit;

a temperature sensor, disposed along the recirculation conduit, for generating a temperature signal indicative of a temperature of the heated water; and

a control unit, coupled to the pump, for changing a speed of the pump based on the temperature signal, wherein the control unit is configured to:

operate the pump at a first speed when the temperature signal is indicative of a value within a first temperature range, wherein the first range is lower than a preselected setpoint temperature;

operate the pump at a second speed when the temperature signal is indicative of a value within a second temperature range, wherein the second range is lower than the first range; and

increase the first speed when the temperature signal falls to the second range.

8. A method for controlling a temperature of water in a recirculating hot water system including a storage tank for storing heated water, a recirculation conduit comprising a supply conduit for supplying the heated water to users via a plurality of outlets having a first outlet and a last outlet and a return conduit for returning an unused portion the heated water to the storage tank, a pump for circulating the heated water, the pump disposed along the return conduit, the method comprising:

measuring, at a point along the recirculation conduit, a temperature of the heated water provided from the storage tank;

controlling a speed of the pump, disposed along the return conduit, based on the measured temperature;

storing a first temperature based on the measured temperature;

increasing the speed of the pump to raise the heated water to a preselected second temperature;

measuring a time elapsed as the measured temperature increases from the first temperature to the preselected second temperature; and

operating the pump for a period of time based at least in part on the time elapsed.

9. The method of claim 8 , wherein the measuring, at a point along the recirculation conduit, a temperature of the heated water provided from the storage tank comprises:

measuring, at a point along the return conduit, a temperature of the heated water provided from the storage tank.

10. The method of claim 8 , wherein the measuring, at a point along the recirculation conduit, a temperature of the heated water provided from the storage tank comprises:

measuring, at a point along the return conduit proximate the pump, a temperature of the heated water provided from the storage tank.

11. The method of claim 8 :

wherein the measuring, at a point along the recirculation conduit, a temperature of the heated water provided from the storage tank comprises:

measuring, at a point proximate the last outlet, a temperature of the heated water provided from the storage tank; and

wherein the last outlet is farther from the storage tank than other outlets of the plurality of outlets.

12. The method of claim 8 , further comprising:

transmitting, using wireless communication, information indicative of the measured temperature; and

receiving, using wireless communication, the information indicative of the measured temperature.

13. A method for controlling a temperature of water in a recirculating hot water system including a storage tank for storing heated water, a recirculation conduit comprising a supply conduit for supplying the heated water to users via a plurality of outlets having a first outlet and a last outlet and a return conduit for returning an unused portion the heated water to the storage tank, a pump for circulating the heated water, the pump disposed along the return conduit, the method comprising:

measuring, at a point along the recirculation conduit, a temperature of the heated water provided from the storage tank;

controlling a speed of the pump, disposed along the return conduit, based on the measured temperature;

operating the pump at a first speed when the measured temperature is within a first temperature range, wherein the first temperature range is lower than a preselected setpoint temperature;

operating the pump at a second speed when the measured temperature is within a second temperature range, wherein the second range is lower than the first range; and

increasing the first speed when the measured temperature falls to the second range.

14. A method for controlling a pump in a recirculating hot water heating system, the method comprising:

measuring, repeatedly, a temperature of water in the hot water heating system;

storing a first temperature based on the measured temperature at a first time;

increasing a speed of the pump to raise the first temperature to a preselected second temperature;

measuring a time elapsed as the measured temperature increases from the first temperature to the preselected second temperature; and

operating the pump for a period of time based at least in part on the time elapsed.

15. The method of claim 14 , wherein the storing a first temperature based on the measured temperature at a first time comprises:

detecting an inflection point indicative of a transition from a decreasing trend in the measured temperature to an increase in the measured temperature; and

storing the measured temperature at the inflection point as the first temperature.

16. The method of claim 14 , further comprising:

storing a setpoint temperature for water in the hot water heating system;

wherein the first temperature is less than the setpoint temperature; and

wherein the preselected second temperature is greater than the setpoint temperature.

17. The method of claim 16 , further comprising:

storing a lower temperature range that is lower than the setpoint temperature; and

storing a time period for pump operation associated with the lower temperature range;

wherein the operating the pump for a period of time based at least in part on the time elapsed comprises:

changing the time period for pump operation to a percentage of the time elapsed; and

operating the pump for the time period for pump operation while the measured temperature is within the lower temperature range.

18. The method of claim 16 , further comprising:

storing a lower temperature range that is lower than the setpoint temperature; and

storing a time period for pump operation associated with the lower temperature range;

storing an upper temperature range that is higher than the setpoint temperature; and

wherein the operating the pump for a period of time based at least in part on the time elapsed comprises:

changing the time period for pump operation to a percentage of the time elapsed when the measured temperature increases to a level within the upper temperature range; and

operating the pump for the time period for pump operation while the measured temperature is within the lower temperature range.

19. The method of claim 14 , wherein the operating the pump for a period of time based at least in part on the time elapsed comprises operating the pump, at a preselected speed, for a period of time based at least in part on the time elapsed.

20. The method of claim 14 :

wherein the measuring, repeatedly, a temperature of water in the hot water heating system comprises measuring, repeatedly, a temperature of water in the hot water heating system at a point along a portion of a return conduit, the portion extending from a last tap along a supply conduit to the pump;

wherein the return conduit is coupled to a supply conduit and to a storage tank;

wherein the supply conduit supplies heated water from the storage tank to a plurality of taps including the last tap;

wherein the return conduit returns an unused portion of heated water to the storage tank.

21. The method of claim 20 , wherein the point along the portion of the return conduit is proximate the pump.

22. The method of claim 14 , further comprising:

storing a setpoint temperature for water in the hot water heating system;

operating the pump at a first speed when the measured temperature is within a first temperature range, wherein the first range is lower than the setpoint;

operating the pump at a second speed when the measured temperature is within a second temperature range, wherein the second range is lower than the first range; and

increasing the first speed when the measured temperature falls to the second temperature range.

23. A method for controlling a pump in a recirculating hot water heating system, the method comprising:

storing a setpoint temperature for water in the hot water heating system;

measuring a temperature of water in the hot water heating system;

operating the pump at a first speed when the measured temperature is within a first temperature range, wherein the first range is lower than the setpoint;

operating the pump at a second speed when the measured temperature is within a second temperature range, wherein the second range is lower than the first range; and

increasing the first speed when the measured temperature falls to the second temperature range.

24. The method of claim 23 , further comprising:

operating the pump at a third speed when the measured temperature is within a third temperature range, wherein the third range is lower than the second range; and

increasing the second speed when the measured temperature falls to the third temperature range.

25. The method of claim 23 :

wherein the measuring a temperature of water in the hot water heating system comprises measuring the temperature of water in the hot water heating system at a point along a portion of a return conduit, the portion extending from a last tap along a supply conduit to the pump;

wherein the return conduit is coupled to a supply conduit and to a storage tank;

wherein the supply conduit supplies heated water from the storage tank to a plurality of taps including the last tap;

wherein the return conduit returns an unused portion of heated water to the storage tank.

26. The method of claim 25 , wherein the point along the portion of the return conduit is proximate the pump.

27. The method of claim 23 , further comprising:

storing a first temperature based on the measured temperature at a first time;

increasing a speed of the pump to raise the first temperature to a preselected second temperature;

measuring a time elapsed as the measured temperature increases from the first temperature to the preselected second temperature; and

operating the pump for a period of time based at least in part on the time elapsed.