Rinnai REU-V2520FFUD ユーザーズマニュアル

Faulty
Thermal Fuse      

Over Temperature Warning 

Outgoing Water 
Temperature Sensor Fault

Heat Exchanger Outgoing 
Temperature Sensor Fault

Combustion Air Temperature 
Sensor Fault

Modulating Solenoid Valve 
Signal Abnormal
Combustion Fan Failure

Water Flow Servo Faulty 
(Does not stop flow properly)

SV0, SV1, SV2, and SV3 
Solenoid Valve Circuit Fault
Flame Sensing Device Fault

Scale Build-up in Heat 
Exchanger   (when checking 
maintenance code history 
“00” is substituted for “LC” )
Nothing happens when 
water flow is activated.

Remedy
Check gas type of unit and ensure it matches gas type being used.
Check for restrictions in air flow around unit and vent terminal. 
Check for low water flow in a circulating system causing short-cycling.
Ensure dip switches are set to the proper position.
Check for foreign materials in combustion chamber and/or exhaust piping.
Check heat exchanger for cracks and/or separations.
Check heat exchanger surface for hot spots which indicate blockage due to scale build up.  Refer to 

instructions in manual for flushing heat exchanger.

Measure resistance of safety circuit.
Ensure high fire and low fire manifold pressure is correct.
Check for improper conversion of product.
Check for restrictions in air flow around unit and vent terminal.
Check for low water flow in a circulating system causing short-cycling.
Check for foreign materials in combustion chamber and/or exhaust piping.
Check for clogged heat exchanger.
Check sensor wiring for damage.
Measure resistance of sensor.
Clean sensor of scale build up.
Replace sensor.
Check sensor wiring for damage.
Measure resistance of sensor.
Clean sensor of scale build up.
Replace sensor.   
Check for restrictions in air flow around unit and vent terminal. 
Check sensor wiring for damage.
Measure resistance of sensor.
Clean sensor of scale build up.
Ensure fan blade is tight on motor shaft and is in good condition. 
Replace sensor.   
Check modulating gas solenoid valve wiring harness for loose or damage terminals.
Measure resistance of valve coil.
Ensure fan will turn freely. 
Check wiring harness to motor for damaged and/or loose connections. 
Measure resistance of motor winding.
Water Flow Servo or wiring faulty. Check Water Flow Servo wiring harness connection.
Measure resistance of Water Flow Servo wiring.
If blank screen is present on remote control then the Water Flow Servo has shorted out.  Unplug Water 

Flow Servo.  If remote lights up and unit starts operating then replace Water Flow Servo.

Check wiring harness to all solenoids for damage and/or loose connections. 
Measure resistance of each solenoid valve coil.
Ensure flame rod is touching flame when unit fires. 
Check all wiring to flame rod for damage.
Remove flame rod and check for carbon build-up; clean with sand paper. 
Check inside burner chamber for any foreign material blocking flame at flame rod.
Measure micro amp output of sensor circuit with flame present.
Replace flame rod. 
Flush heat exchanger.  Refer to instructions in manual.
Replace heat exchanger. 

 
Clean inlet water supply filter.
On new installations ensure hot and cold water lines are not reversed. 
Check for bleed over. Isolate unit from building by turning off hot water line to building.  Isolate the 

circulating system if present.  Open your pressure relief valve; if unit fires, there is bleed over in your 
plumbing. 

Ensure you have at least the minimum flow rate required to fire unit. 
Ensure turbine spins freely. 
Measure the resistance of the water flow control sensor. 
Remote control does not light up but you have 12 VDC at the terminals for controls. 

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