Water heater with continuously variable air and fuel input

摘要

A water heater apparatus (10) includes a water conduit (12) having an inlet (14) and an outlet (16). A primary heat exchanger (18) has a water side defining a portion of the water conduit. A burner (28) is operatively associated with the primary heat exchanger (18) for heating water in the water side of the primary heat exchanger. A variable flow blower (30) provides pre-mixed combustion air (34) and fuel gas (36) to the burner (28) at a controlled blower flow rate within a blower flow rate range. This apparatus allows the heat output of the water heater to be continuously varied within a substantial flow rate range having a turn down ratio of as much as four to one.