- 5 -
1-5 Main Component Structures
1. Gas flow control device
• Feeds the necessary amount of gas to heat water to a set temperature, based on the
amount of water flowing in through the inlet measured by the water flow sensor and the
water temperature calculation.
• When the thermistor detects the water temperature at the inlet, the temperature is com-
pared with the setting. An electric current representing the temperature difference is
transmitted to the PCB where the current is amplified and dispatched to the Modulating
Solenoid Valve.
• An electromagnetic force caused by the current from the PCB pushes the plunger up-
ward. <Upward force>
• Pressure received at the diaphragm due to internal pressure in the chamber of the
Modulating Solenoid Valve pushes the plunger downward. <Downward force>
• The plunger stops moving and stays at a certain position when the Upward and Down-
ward force are balanced.
• As the plunger remains at the position, the valve position of the Modulating Solenoid
Valve linked to the plunger is determined. This determines a "clearance" between the
valve body and the Modulating Solenoid Valve, establishing a necessary gas quantity.
The required amount of gas is then supplied to the main burner.
• If the temperature of the heated water is lower or higher than the setting, the resistance
of the hot water temperature detecting thermistor changes accordingly to automatically
adjust the gas amount by changing greater or lower the current transmitted to the Modu-
lating Solenoid Valve. This stabilizes the heated water temperature.
• When the gas supply pressure is changed, the receiving pressure of the diaphragm
changes and also changes the clearance between the valve body and the Modulating
Solenoid Valve. The gas is controlled to remain at a constant level.