Patent ID: 8191513

Claim:
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.