Patent ID: 8186312

Claim:
A water heater system, comprising: a modulating water heater continuously operable over a range of heat outputs from a minimum firing point to a maximum heat output; and a controller operably associated with the heater for modulating the heat output of the heater within the range, the controller comprising: a water temperature signal receiving input for receiving a signal indicative of water temperature in a water flow system receiving water from the heater; a water temperature setpoint input for receiving an input of a setpoint for the water temperature in the water flow system; a control logic operable to control the heater as one of a plurality of modulating heaters in a cascade arrangement, the control logic being operable to designate an operating sequence of the heaters, the control logic being operable to define a combined operating range of the plurality of heaters including a deadband between a maximum output of one heater and the sum of said maximum output of said one heater plus a minimum output of the sequentially next heater, said control logic being operable when a system heat demand falls within the deadband to allow the sensed water temperature to vary at least within a temperature range spanning the temperature setpoint before the sequentially next heater is turned on or off.