Rinnai REU-1110FFU(F)-E, Installation And User Manual

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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 3 steps
(1 step on model REU
- 1110FFU - E). This gives the burner more steady combustion at the
required capacity and allows the water heater to operate at very low flow rates and tempera-
ture 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 flame, and never from
the flame 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 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 over heating and heat exchanger splits where
water may leak out and be super heated into steam.
4. Overheat Safety (Bi-metal Switch).
This bi - metal switch is fixed at the bend of the heat exchanger hot water outlet. If the temper-
ature outlet from the heat exchanger reaches 90°C the bi - metal switch will open and the so-
lenoid valve circuit is broken. This will cease combustion in case of overheat.
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 compared to the cur-
rent required to attain that speed for air proving. If the fan current is over or under the param-
eters for the given speed the unit will shut down on air proving.
6. Water Flow Controller.
The water flow controller has Shape Memory Alloy built - in.
The shape memory alloy varies with the temperature of incoming water: this will limit the
maximum hot water flow and will limit the water flow further when the burner is at high fire to
ensure the temperature setpoint is met.