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Rinnai · Tankless water heater

SS Service Soon alert (also listed as 55)

Low severity SENSEI RX/CXSENSEI

What the control is telling you

Time-based service reminder configured at installation (Parameter 03). It means the unit is due for service and the heat exchanger should be flushed.

Applies to: SENSEI Series, SENSEI RX/CX Series

Likely causes

  • Service interval set in Parameter 03 has elapsed
  • Heat exchanger due for flushing (scale risk with hard water)

Test and repair steps

  1. Flush the heat exchanger to prevent damage (owner's manual section 6.3, Flushing the Heat Exchanger).
  2. Treat hard water to prevent scale build-up and heat exchanger damage.
  3. SENSEI Reset SS by pressing the On/Off button on the temperature controller five times within five seconds.
  4. SENSEI RX/CX Reset SS by pressing and holding the "A" button until SS clears.
  5. Confirm Parameter 03 is set as intended A = not active, B = 0.5 yr, C = 1 yr, D = 2 yrs (see owner's manual section 4.12 for SENSEI, 4.13 for SENSEI RX/CX).

Settings for these units

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Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.66. Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.