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Rinnai Water Heater Error Codes

Rinnai tankless water heaters show a two-digit code such as 11 or 12 on the temperature controller, and LC codes when scale is building up. Below are 31 Rinnai codes across 2 model series. Each one says what it means, which series it applies to, what you can safely check, and when to call a licensed pro, with a link to the Rinnai document it comes from.

The same code can mean different things on different series, so match the series column to your unit. Your unit's manual is the final word. Reviewed October 2026.

🔎 Enter the code, blink count or model shown on your unit

31 codes

All Rinnai error codes

Code	Meaning	Applies to	Safety
03 Code shown on the temperature controller display	Power interruption during bath fill	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🧭 Check first
05 Code shown on the temperature controller display	By-pass flow control	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
10 Code shown on the temperature controller display	Air supply or exhaust blockage, or condensate trap full	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
11 Code shown on the temperature controller display	No ignition	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🧭 Check first
12 Code shown on the temperature controller display	No flame	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🧭 Check first
14 Code shown on the temperature controller display	Heat exchanger overheat	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
15 Code shown on the temperature controller display	Venturi control	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
16 Code shown on the temperature controller display	High outgoing temperature	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
17 Code shown on the temperature controller display	Venturi blockage	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
19 Code shown on the temperature controller display	Electrical grounding	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
21 Code shown on the temperature controller display	Data transfer error	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
25 Code shown on the temperature controller display	Condensate pump (accessory)	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🧭 Check first
32 Code shown on the temperature controller display	Outgoing thermistor	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
33 Code shown on the temperature controller display	Heat exchanger thermistor	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
38 Code shown on the temperature controller display	Exhaust thermistor	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
41 Code shown on the temperature controller display	Freeze protection thermistor	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
51 Code shown on the temperature controller display	Inlet thermistor	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
52 Code shown on the temperature controller display	Gas valve	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
54 Code shown on the temperature controller display	High exhaust gas temperature	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
61 Code shown on the temperature controller display	Combustion fan	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
63 Code shown on the temperature controller display	Recirculation low flow	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🧭 Check first
65 Code shown on the temperature controller display	Water flow control	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
70 Code shown on the temperature controller display	PC board	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
71 Code shown on the temperature controller display	Solenoid valve circuit	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
72 Code shown on the temperature controller display	Flame rod	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	🛑 Call a pro
FF Code shown on the temperature controller display	Maintenance indicator	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	✅ Keep running
SS SS (shown on the controller)	Service soon (flush heat exchanger)	SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)	✅ Keep running
02 Code shown on the temperature controller display	No burner operation during freeze protection mode	RL75i (VB2528FFUD-US) and RL94i (VB2735FFUD-US) tankless water heaters	🛑 Call a pro
LC Code shown on the temperature controller display	Scale build-up in heat exchanger	RL75i (VB2528FFUD-US) and RL94i (VB2735FFUD-US) tankless water heaters	🧭 Check first
31 Code shown on the temperature controller display	Burner sensor error	RL75i (VB2528FFUD-US) and RL94i (VB2735FFUD-US) tankless water heaters	🛑 Call a pro
73 Code shown on the temperature controller display	Burner sensor circuit error	RL75i (VB2528FFUD-US) and RL94i (VB2735FFUD-US) tankless water heaters	🛑 Call a pro

✅ Usually fine to keep running · 🧭 Check a few things first · 🛑 Turn it off and call a licensed pro

Find your Rinnai model series

The codes Rinnai documents for each series we have checked. If your series is not listed, the code may mean something different on your unit, so check its manual.

RL75i (VB2528FFUD-US) and RL94i (VB2735FFUD-US) tankless water heaters

02 LC 31 73

SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor)

03 05 10 11 12 14 15 16 17 19 21 25 32 33 38 41 51 52 54 61 63 65 70 71 72 FF SS

More Rinnai codes

Rinnai 05: By-pass flow control

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The manual lists the by-pass flow control as the item to check. It tells a professional to measure its resistance and replace it if needed.

When to call a pro: Call a trained and qualified professional (or Rinnai customer support). Do not open the unit.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.73

Rinnai 15: Venturi control

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The manual lists the venturi control. It says to check the venturi motor, replace the gas valve assembly if needed, and clear the code by resetting main power.

When to call a pro: Call a trained and qualified professional (or Rinnai customer support). Do not open the unit.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 17: Venturi blockage

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The manual says to follow the Code 10 solutions first, then make sure the venturi is not blocked.

When to call a pro: Call a trained and qualified professional (or Rinnai customer support). Do not open the unit.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 19: Electrical grounding

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The manual says to check all components for electrical short.

When to call a pro: Electrical shorts need a qualified professional. Turn the unit off and do not open it.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 21: Data transfer error

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The manual says if the PCB has been replaced, make sure the data transfer process was completed.

When to call a pro: Call the professional who serviced the board, or a qualified professional.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 33: Heat exchanger thermistor

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The heat exchanger temperature sensor has a fault. The manual says to follow the Code 32 steps.

When to call a pro: Call a trained and qualified professional (or Rinnai customer support). Do not open the unit.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 38: Exhaust thermistor

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The exhaust temperature sensor has a fault. The manual lists checking wiring, measuring resistance and replacing the sensor.

When to call a pro: Call a trained and qualified professional (or Rinnai customer support). Do not open the unit.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 41: Freeze protection thermistor

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The freeze protection sensor has a fault. The manual says to follow the Code 38 steps.

When to call a pro: Call a trained and qualified professional (or Rinnai customer support). Do not open the unit.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 51: Inlet thermistor

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The inlet water temperature sensor has a fault. The manual lists checking wiring, measuring resistance, cleaning scale and replacing the sensor.

When to call a pro: Call a trained and qualified professional (or Rinnai customer support). Do not open the unit.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 52: Gas valve

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The manual lists the gas valve. It tells a professional to check the flame rod and wire and the gas solenoid valve, and to call Rinnai technical department.

When to call a pro: Call a trained and qualified professional (or Rinnai customer support). Do not open the unit.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 54: High exhaust gas temperature

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The exhaust gas temperature is high. The manual says to keep the heat exchanger fins clean, confirm the inlet water temperature is not too high, ensure condensate is not blocked and reset main power.

When to call a pro: If the code returns, call a qualified professional. Heat exchanger fin cleaning is not a homeowner task.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 63: Recirculation low flow

🧭 Check a few things first

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

Recirculation flow is low. The manual lists the bypass plug and filter, clean inlet water and bypass filters, parameter settings, pump voltage and air in the recirculation line.

When to call a pro: If the filters are clean and the code remains, call a qualified professional about the recirculation setup.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai 70: PC board

🛑 Turn it off and call a licensed pro

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

The manual lists the PC board and says to replace it.

When to call a pro: Call a trained and qualified professional (or Rinnai customer support). Do not open the unit.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.74

Rinnai FF: Maintenance indicator

✅ Usually fine to keep running

Applies to: SENSEI N Series residential condensing: RU199i, RU180i, RU160i, RU130i (indoor) and RU199e, RU180e, RU160e, RU130e (outdoor). Shows as: Code shown on the temperature controller display

This is a placeholder in the diagnostic code history showing that a service provider performed maintenance or service. It is not a fault.

When to call a pro: Not a fault. Ask your service provider if you want to know what service was done.

Source: Rinnai SENSEI N Series Residential Installation and Operation Manual (100000467), 5.6 Diagnostic Codes, p.75

Rinnai 02: No burner operation during freeze protection mode

🛑 Turn it off and call a licensed pro

Applies to: RL75i (VB2528FFUD-US) and RL94i (VB2735FFUD-US) tankless water heaters. Shows as: Code shown on the temperature controller display

The unit did not run the burner during freeze protection mode. The sheet's action is a service call.

When to call a pro: Call a qualified service professional, as the sheet says.

Source: Rinnai RL75i / RL94i Quick Reference sheet U287-1817x01(00), Error Codes

Rinnai 31: Burner sensor error

🛑 Turn it off and call a licensed pro

Applies to: RL75i (VB2528FFUD-US) and RL94i (VB2735FFUD-US) tankless water heaters. Shows as: Code shown on the temperature controller display

The burner sensor has an error. The sheet says to measure the sensor's resistance and replace the sensor.

When to call a pro: Call a qualified professional.

Source: Rinnai RL75i / RL94i Quick Reference sheet U287-1817x01(00), Error Codes

Rinnai 73: Burner sensor circuit error

🛑 Turn it off and call a licensed pro

Applies to: RL75i (VB2528FFUD-US) and RL94i (VB2735FFUD-US) tankless water heaters. Shows as: Code shown on the temperature controller display

The burner sensor circuit has an error. The sheet says to check sensor wiring and the PCB and replace the sensor.

When to call a pro: Call a qualified professional.

Source: Rinnai RL75i / RL94i Quick Reference sheet U287-1817x01(00), Error Codes

Safe first steps for any code

Write down the exact code shown on the controller or the number of status light flashes.
Turn the water heater power off and back on (or press the reset button the manual describes) once. If the code comes back, stop resetting.
Make sure the gas supply valve to the heater is open and other gas appliances in the home are working.
Make sure the cold water supply valve is fully open and hot water taps are not partly closed.
Look at the outside vent terminal for snow, ice, leaves or anything blocking it (look only).

🛑 Stop and call a licensed pro if

You smell gas. Leave the house, do not touch switches, and call your gas utility from outside.
Codes for flame failure, overheating, venting or the control board that return after one reset.
Water leaking from the heater, the relief valve discharging, or scorching around the burner area.
A carbon monoxide alarm sounds. Get everyone outside and call 911 or the fire department.

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