Rinnai Water Heater Service Manual 7 100000098 Rev B
Diagnostic Codes
The Rinnai water heater has the ability to check its own operation continuously. If a fault occurs, an error code
will flash on the display of the remote controller. This assists with diagnosing the fault and may enable you to
overcome a problem without a service call.
Some of the checks below may need to be done by a qualified service technician. Call a
service technician for any remedy that involves gas or electricity. Call a service
technician if you have any doubt or reservation about performing the remedy yourself.
WARNING
Accessing Operating Information
To display the most recent error codes press and hold the “On/Off” button for 2 seconds. While holding the “On/
Off” button press the ▲ button. The last 9 error codes will flash one after the other. To exit this mode press the
“On/Off” and ▲ button as before.
To display the water flow through the water heater press and hold the ▲ button for 2 seconds and without
releasing the ▲ button press the “On/Off” button.
To display the outlet water temperature press and hold the ▼ button for 2 seconds and without releasing the ▼
button press the “On/Off” button.
Models MC-91 and MCC-91
1. Water Flow Begins.
• Water Flow Sensor sends pulses to the PC
Board.
• PC Board senses flow.
• Firing Sequence begins when the flow exceeds
the minimum activation flow rate.
2. Firing Sequence.
• PC Board monitors inlet/outlet water
temperature, temperature set point, and water
flow rate.
• Combustion fan energized. Purges combustion
chamber.
• Spark igniter begins sparking.
• Gas control valve opens to minimum fire rate.
• Flame rod(s) proves ignition.
• Spark igniter stops sparking.
3. Normal Operation.
• PC Board monitors flame rod, fan motor
frequency, outlet water temperature, controller
temperature set point and water flow rate.
• Gas control valve modulates gas input to
required firing rate.
• Combustion fan speed is adjusted for the
required firing rate.
• Water flow control valve is adjusted as needed.
4. Shut-down Sequence.
• Shut-down begins when the PC Board senses
the minimum flow rate which is 0.26 - 0.5 gpm
depending on model.
• Gas control valve closes.
• Water flow control valve resets to standby
position.
• Combustion fan runs for a short period of time
at low speed.
5. Standby Mode.
• PC Board monitors water temperature and
remote controls.
• Freeze protection is activated as needed.
Operation
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