Main Components - Rinnai HDC 1600i Low NOX Installation And User Manual

MAIN COMPONENTS

1. Gas Control Unit
1.1 Modulating Valve
This device is used by the PCB to adjust the volume of gas to the burner in proportion to the
volumetric flow rate of water in order to maintain a supply of constant temperature hot water
amid changes in water flow rates and incoming temperatures.
1.2 Change-over Solenoid Valves
Additional solenoid valves are included to section the burner and stage the control in 4
steps. This gives the Burner more steady combustion at the required capacity and allows
the water heater to operate at very low flow rates and temperature rises.
2. Flame Rod
Monitors combustion characteristics inside the combustion chamber. If the flame fails, gas
supply is stopped. Works through rectification of the combustion flame. An AC voltage is
supplied to the flame rod. Electrons can only pass from the rod to the earthed burner through
the flame, and never from the burner to the rod, so the resultant DC current is used to prove
combustion. When the DC current is present the burner has normal combustion, if the DC
current is not present (or an AC current is present) the unit shuts the solenoid valve.
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 thermal fuse must
be replaced if it melts. It is to protect against overheating and heat exchanger splits where
water may leak out and be superheated into steam.
4. Overheat Safety (Bi-metal Switch)
Several Bi-metal Switches are fixed to the main heat exchanger and above the combustion
chamber. If the temperature reaches 97°C the bi-metal switches will open and the solenoid
valve circuit is broken. This will cease combustion in case of overheat.
5. Combustion Fan
The combustion fan supplies primary and secondary air to the ceramic plate burner. 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 compared 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 Flow and Bypass Servos 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 and Bypass Servo
Water flow control is achieved through the use of servo driven water flow and bypass valves.
Both servo motors are controlled by the PCB. The 'Water Flow Valve' restricts the flow of
water into the heat exchanger assembly if the programmed temperature cannot be achieved.
This will limit the maximum water flow, and will limit the hot water flow further when the
burner is at high fire to ensure the temperature setpoint is met.
During normal operation at low (less than 60°C) setpoint, cold water from the inlet valve is
mixed with hot water from the heat exchanger outlet. The 'Bypass Valve' mixes the correct
proportion of cold and hot water to ensure accurate hot water delivery temperature over the
available range of flow rates. For temperature setpoint over 60°C the bypass servo will be
shut. The water flow and bypass valves are a combined assembly on the cold water inlet of
the appliance.
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