MAIN COMPONENTS
3. Thermal Fuse
The thermal fuse is an electric link which must be intact for the unit to operate. If the thermal fuse reaches a set temperature it will melt and the unit will shut down. The ther- mal fuse must be replaced if it melts. It is to protect against over heating and heat ex- changer splits where water may leak out and be super heated into steam.
4. Overheat Safety
This
5. Combustion Fan
The combustion fan supplies primary air into the wing burners and secondary air up through the Bunsen style burners. The fan is DC low voltage and the speed is controlled by the PCB depending on the hot water supply and temperature. The fan speed is com- pared to the current required to attain that speed for air proving. If the fan current is over or under the parameters for the given speed the unit will shut down on air proving.
6. Water Volume Servo with Water Flow Sensor
6.1 Water Flow Sensor
Water flow sensing is done with a small turbine that spins when water travels through it in the correct direction. Each of the four fins on the turbine has a small magnet on it. Outside of the valve there is a magnetic sensor that detects the speed that the turbine is revolving. The revolution speed is input to the PCB which relates this speed to the water flow volume and determines whether it is sufficient for ignition.
6.2 Water Volume Flow Servo
The water volume is adjusted by opening and closing the water flow valve with the servo motor. This will limit the maximum hot water flow to 20 L/min, and will limit the water flow further when the burner is at high fire to ensure the temperature setpoint it met.
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