Rinnai Error Code 55: Rinnai Code 55 - False Fire Detection

Severity
Critical
Type
digital display
Estimated repair cost: $100 — $350 (parts + labor)
Warning: A 'false fire' condition can indicate a serious safety issue. Shut down the unit immediately and call a qualified technician.

How to Fix Rinnai Code 55

  1. Step 1: Immediately turn off the gas supply to the Rinnai unit at the gas shut-off valve.
  2. Step 2: Turn off the electrical power to the unit at the breaker.
  3. Step 3: Contact a qualified HVAC technician or Rinnai-certified service provider to inspect and repair the unit. Do not attempt to troubleshoot or repair the unit yourself.

How to Reset Rinnai Code 55

  1. Turn off the unit using the power button on the front panel.
  2. Turn off the gas supply valve.
  3. Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
  4. Restore power at the breaker, then open the gas valve.
  5. Turn the unit back on. If the error returns, the underlying issue needs repair.

What does 55 mean?

Rinnai error code 55 indicates that the unit's flame sensor is detecting a flame when it shouldn't be. This can happen either before a call for heat, or after the unit is already off. This is a critical safety issue because it could mean that gas is leaking into the combustion chamber and creating a risk of uncontrolled ignition or carbon monoxide poisoning. It's important to address this immediately to prevent potential hazards and further damage to your Rinnai tankless water heater.

Essentially, the unit 'thinks' it sees a flame when it shouldn't. The control board relies on the flame rod sensor to confirm the presence of a flame during normal operation. If the flame rod is sending the wrong signal, the control board can get confused and shut down the unit as a precaution.

Affected Models

Replacement Parts

PartOEM NumberEst. Cost
Flame Rod Sensor 273000014 —
Gas Valve — —
Main Control Board (PCB) — —

Related Codes on Same Models

CodeDescriptionSeverity
02 Stagnant Water Detection Warning
10 Air Supply/Exhaust Blockage Warning
11 No Ignition Warning
12 Flame Failure Warning
14 Thermal Fuse Warning
16 Over-Temperature Warning
19 Electrical Grounding Warning
25 Condensate Overflow Warning
29 Condensate Neutralizer Warning
31 Inlet Thermistor Failure Warning