Rinnai 52
Rinnai code 52: gas valve signal fault
Short answer
Code 52 is a gas valve fault. On older Rinnai models it is described as an abnormal signal from the modulating solenoid valve, the part that adjusts gas flow to control flame size. Technicians check the wiring and valve coil resistance and voltage, then replace the gas valve or the control board.
A tankless heater constantly adjusts its flame to hold the water at your set temperature. The modulating gas valve does that job. Code 52 means the control board is getting an abnormal signal from that valve or its circuit.
Rinnai makes several generations of tankless heaters (SENSEI, SENSEI RX/CX and older non-SENSEI models). The meaning below comes from Rinnai's own diagnostic code guide; the exact service steps differ slightly between generations.
If you smell gas, do not reset the unit or touch any switches. Leave the building and call your gas utility from outside.
What a technician checks
- The wiring harness between the gas valve and the control board, for loose or damaged terminals.
- The flame rod and its wiring, which Rinnai lists first on newer SENSEI models.
- The resistance of the valve coil and the voltage reaching the valve while the unit tries to fire.
If the coil or voltage is out of specification, the gas valve is replaced. On older models, if the valve checks out but the code persists, Rinnai's next step is the control board.
After a gas valve replacement
On SENSEI models, Rinnai describes a reset procedure on the control board that may be needed if code 52 still appears after the new valve is installed. A trained technician should handle this.
What homeowners can do
Very little on this code. Reset the unit once from the controller. If code 52 returns, turn the heater off and call a licensed installer. Do not try to adjust the gas valve: manufacturers generally treat tampering with it as grounds to refuse warranty claims, and it is a safety risk.
See the full list on our Rinnai error codes page.
Common questions
Can I fix Rinnai code 52 myself?
No. It involves testing and replacing the gas valve, which is work for a licensed technician.
Is Rinnai code 52 covered by warranty?
It depends on the age of the unit and the warranty terms for your model. Check your registration before paying for parts.
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Other Rinnai codes
| Code | Meaning |
|---|---|
| 02 | No burner operation during freeze protection |
| 03 | Power interruption during bath fill |
| 05 | Bypass flow control device fault |
| 10 | Air supply, exhaust blockage or condensate trap full |
| 11 | No ignition |
| 12 | Flame failure |
| 14 | Thermal fuse or overheat sensor tripped |
| 15 | Venturi control fault |
| 16 | Outgoing water temperature too high (safety shutdown) |
| 17 | Venturi blockage |
| 19 | Electrical grounding fault |
| 21 | Data transfer error after a control board replacement |
| 25 | Condensate drain clogged or condensate pump error |
| 32 | Outgoing water temperature sensor (thermistor) fault |
| 33 | Heat exchanger temperature sensor (thermistor) fault |
| 34 | Combustion air temperature sensor fault |
| 38 | Exhaust gas temperature sensor fault |
| 41 | Freeze protection sensor fault |
| 51 | Inlet water temperature sensor fault |
| 52 | Gas valve or modulating solenoid valve signal fault |
| 54 | High exhaust gas temperature |
| 57 | Burner overheat switch open |
| 58 | Secondary heat exchanger overheat |
| 61 | Combustion fan motor fault |
| 63 | Recirculation low flow |
| 65 | Water flow control device (servo) fault |
| 70 | Control board (PC board) fault |
| 71 | Gas solenoid valve circuit fault |
| 72 | Flame rod (flame sensing) fault |
| 73 | Burner thermocouple fault |
| 79 | Water leak detected inside the unit |
| LC | Scale buildup in the heat exchanger |
| SS | Service soon (maintenance reminder) |
| FF | Maintenance has been performed (service history marker) |