Since Rinnai water heaters are one of the most advanced tankless water heaters available, we recommend to contact a service technician that’s authorized to work on Rinnai water heaters.
Each Rinnai unit uses a temperature controller (either MC-91-1 or MC-91-2) on the front panel to display various configuration options for installation as well as error codes for when problems arise. The previous nine error codes are stored in memory. To access these codes, hold the ON/OFF button for two seconds and simultaneously press the UP arrow.
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