Patent ID: 7164851
Filing Date: 2007-01-16
Classification: F24H

Abstract:
1. Control circuitry for a tankless water heater system, the tankless water heater system including a plurality of water conduits connected in series, the series connection being further connectable to a cold water supply and to provide a heated water flow to a heated water demand site, the control circuitry comprising: a plurality of water heater elements, one each associated with each of the plurality of water conduits; a controller including a central processing unit with an operating program; a plurality of sensors positioned in the water flow and electrically coupled to the controller, at least one of the plurality of sensors providing an indication of the water temperature in an outlet of the series connection; connecting and operating circuitry coupling each of the plurality of water heater elements to the central processing unit; and the central processing unit being programmed to control the connecting and operating circuitry in accordance with indications from the plurality of sensors to individually and sequentially activate a first of the plurality of water heater elements in predetermined steps to a middle power level of the first water heater element less than a maximum power level of the first water heater element, activate a second of the plurality of water heater elements in predetermined steps to a middle power level of the second water heater element less than a maximum power level of the second water heater element, and activate the first water heater element from the middle power level of the first water heater element to the maximum power level of the first water heater element and then activate the second water heater element from the middle power level of the second water heater element to the maximum power level of the second water heater element in response to a demand for heated water, the number of the plurality of water heater elements sequentially activated and the sequential power level of the activation being determined by the demand for heated water.