Rinnai REU-2007W, Service Manual

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Situated to the right of the burner at the front, the flame rod monitors combustion, preventing any
discharge of gas to the burner if there is no flame, by sending a signal to the PCB which in turn
isolates the gas.
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Also referred to as an Over Heat Switch. This device is fitted to a bend section at the inlet to the heat
exchanger. If the flame remains on the burner after the tap is closed, and the water temperature
inside the heat exchanger reaches 97 C, an DC 12 volt bi-metal cut-off switch isolates the gas to the
solenoids.
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Should the incoming water flow become restricted or stop, then the water flow sensor will cease to
send a magnetic pulse signal to the PCB, in turn isolating the flow of gas to the burner.
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Wrapped around the entire surface of the heat exchanger, if the heat exchanger burns out, or the
temperature outside it reaches 129 C, the thermal fuse melts, breaking the electronic circuit. Current
to the gas solenoid valve circuit is cut, and combustion stops, shutting down the unit.
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This spring and valve seating type valve located on the hot water outlet will release the built up
pressure if the pressure inside the heat exchanger reaches 2100 kPa until 1500 kPa is maintained.
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The combustion fan rpm are continually monitored by a magnetic pulse counter connected to the
PCB. If the fan revolutions deviate from the speed required for complete combustion, a signal is sent
to the PCB and the revolutions adjusted accordingly. (If not the unit shuts down)
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When the outdoor temperature drops and the temperature inside the appliance below 3.5 C, the
frost sensing device is activated, and the anti-frost heaters prevent the water in the appliance from
freezing. These anti-frost heaters remain ON until the temperature inside the appliance rises to
11.5 C. There are 5 x 16 Watt anti-frost heaters located at various points in the main water flow area
of the appliance. The anti-frost protection device will prevent freezing down to -20 C in a no wind
situation, and -15 C in a windy situation.
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The temperature of the outgoing hot water is constantly monitored by the water temperature
thermistor located near the outlet of the appliance. If the outgoing water temperature reaches 3 C
above the preset temperature, the burner will automatically go out. The burner will only ignite again
once the outgoing hot water temperature falls below the preset temperature.
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