Rinnai code 15: venturi control fault

Rinnai's SENSEI heaters use a venturi to control the gas and air mixture across a wide firing range. Code 15 means the control board has lost proper control of it.

The meaning and service steps below come from Rinnai's own diagnostic code guide for its tankless water heaters.

Rinnai lists this code for SENSEI and SENSEI RX/CX series.

What you can do

1. Turn off the power to the heater, wait a minute and turn it back on.
2. If code 15 returns, leave the unit off and call a technician.

What a technician checks

• The gas valve and solenoid wiring harnesses for loose, damaged or broken connections
• On RX/CX models, whether a reed switch on the back of the gas valve is seated properly
• Voltage and resistance readings at the control board, against Rinnai's specifications

Depending on those readings, the venturi control parts or the control board are replaced.

Before you call

Have the model and serial number from the rating label ready, along with the exact code and when it appears: at startup, during use, or only at high demand. Mention any recent work on the gas, water or electrical supply and when the heater was last descaled. This helps the technician bring the right parts and often saves a second visit.

See every code on our Rinnai error codes page.