Control system for modulating water heater

A water heating system, comprising:

• a water supply system;
• a flow meter connected to the water supply system and configured to provide a water flow rate signal corresponding to a water flow rate;
• a modulating water heater connected to the water supply system for heating water for the water supply system, the modulating water heater being a gas fired water heater including:
• a variable output radially outwardly firing elongated burner;
• a fin tube heat exchanger arranged concentrically about the burner such that water flowing through the heat exchanger receives heat from the burner radiating directly upon exterior fins of the fin tube heat exchanger;
• a water inlet to the heat exchanger;
• a water outlet from the heat exchanger;
• a control valve upstream of the water inlet for controlling flow of water into the water inlet;
• and
• a blower including a variable speed drive motor, the blower being configured to provide a variable flow of premixed gas and combustion air to the burner;
• and
• a controller configured to:
• receive the water flow rate signal from the flow meter;
• control modulation of the modulating water heater by controlling a speed of the variable speed drive motor of the blower, and thereby controlling the flow of premixed gas and combustion air to the burner in response at least in part to a change in the water flow rate signal;
• and
• control the control valve and thereby control the flow of water to the water inlet.