Rinnai code 02: no burner operation during freeze protection

Some older Rinnai tankless heaters protect themselves from freezing by briefly firing the burner to warm the water inside. Code 02 means the heater tried to do that and the burner did not operate.

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

Rinnai lists this code for its non-SENSEI series only.

Why it matters in cold weather

If freeze protection is not working, water inside the heat exchanger can freeze and crack it, which is one of the most expensive tankless repairs. Treat code 02 in winter as urgent.

What Rinnai tells technicians to check

• All gas valves are open and supplying the right pressure
• Air was purged from the gas lines after installation
• The inlet gas pressure meets the minimum on the rating plate with every gas appliance firing
• The gas type at the house matches the unit, and the gas type setting on the control board is correct
• The igniter sparks, and the gas valve works

What you can do now

1. Check that other gas appliances work and the gas valve to the heater is open.
2. On propane, check the tank level.
3. Keep power on to the heater. If you cannot get it running and a hard freeze is coming, ask your technician how to drain the unit to protect it.

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.