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3. Service and Maintenance
3-1 Operation Principles
[Before operation]
• When ON/OFF Button (Power switch) on the remote controller is turned ON, the ON
indicator iluminates (in the case of operation with a remote controller). Gas is
supplied to the Gas Valve.
[During operation (when hot water is supplied)]
• When the hot water supply tap is opened, water flows through the Water Flow
Control Valve (with sensor) into the Heat Exchanger Assembly. The water heated by
the Heat Exchanger Assembly passes through the Outgoing Water Temperature
Sensor to go to a hot water outlet. At this time, the Water Flow Sensor detects
water flow. Then the PCB starts the Fan Motor, activating the electrode. The Main
Gas Valve, Gas Valve 1 and Gas Valve 2 are opened simultaneously when the spark
is emitted by the Electrode.
• The gas supply is set at the slow ignition level by the Gas Control Valve and goes to
Burners. When Burners are ignited, the Flame Sensor detects the flame condition,
the “
In Use
” Indicator lights and the sparking is stopped.
• The PCB detects the water flow rate based on the signal from the Water Flow Sensor,
calculates the energy required to heat the water up to the set temperature, and
adjusts the opening position of the Gas Control Valve and the Fan Motor rpm.
After this, PCB maintains the combustion to keep the water at the set temperature by
checking with the Outgoing Water Temperature Sensor, while controlling the Fan
Motor rpm and gas supplied by the Gas Control Valve. (Feedforward feedback
control)
[Operation stop]
• When the hot water tap is closed, the Water Flow Sensor detects no water flow. In
response to this, PCB closes all the Gas Valves and the Fan Motor stops after
running for 65 seconds. (Post purge)
