Rinnai FUA-E, Service Manual, Page: 8 / 67

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• Heat Exchanger Thermistor : Measures hot water temperature at heat exchanger outlet. If
water temperature reaches a predetermined limit, gas supply is stopped.
• Hot Water Delivery Thermistor : Measures hot water temperature at the outlet valve (i.e. the
‘mixed’ temperature).
•
Flame Rod : Monitors combustion characteristics inside the combustion chamber. If the flame
fails, gas supply is stopped.
• Overheat Switch : Situated on the heat exchanger, gas supply is stopped when water
temperature reaches 97ºC for a number of seconds.
•
Fusible Link : Situated on the heat exchanger, electrical power supply is stopped if the
temperature exceeds 150ºC.
• Water Pressure Relief Valve : Safeguards the water circuit against excessive inlet pressure.
Opens at 15 bar, closes at 12 bar.
• Electrical Fuse : (3A glass fuse) prevents against over-current. Surge Protector: prevents
against over-current.
•
Boil Dry Prevention : If water flow sensor detects no flow, gas supply is stopped.
• Combustion Fan Speed Sensor : In case of combustion fan defect (no rotation of fan) gas
supply is stopped.
• Temperature Cutout : If the delivered hot water temperature rises above the required delivery
temperature for a number of seconds, the gas supply is stopped.
Sensors and Safety Devices
Combustion Specifications
The secondary gas pressure is set with the cover off the unit and a manometer measuring
the pressure from the gas valve (regulator) test point
Gas Type
Injector
size
(mm)
Primary
Pressure (mbar)
Secondary Pressure
(mbar)
Gas Input [Gross]
(kW)
Low High Low High
Natural Gas
(G20)
1.3 20 1.8 9.0 4.7 34.9
Propane (G31) 37 2.2 14.2 4.9 36.5
Damper
Nat Gas
LPG