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Rinnai · Combi boiler

763 0-10V external control input over-voltage

Medium severity I-Series Plus 175K and higher

What the control is telling you

The External Controls terminal is receiving more than 10 volts from the 0-10V controller.

Applies to: I-Series Plus boilers — 175K BTU and higher only (Combi and Solo)

Likely causes

  • Incompatible external controller
  • Damaged external controller
  • Incorrect external controller settings
  • Parameter 55 not set to match the application

Test and repair steps

  1. Measure voltage at the External Controls terminal; above 10 V means the controller is incompatible or damaged and must be replaced.
  2. Review the external controller's settings.
  3. Confirm Parameter 55 A = not active; b = 36°F (20°C) Delta T range; C = 54°F (30°C); d = 72°F (40°C). With 0-10V control, the set temperature is driven by the input voltage.
  4. Note heating starts once input exceeds 2 V. Compare against the 0-10V example chart in the source manual (p.43).

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Source: Rinnai Troubleshooting I-Series Plus Boiler Diagnostic Codes (800000375), p.42–43. Summarized in our own words; check the original manual for your model.

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