Rinnai code 12: flame failure

Where code 11 means the burner never lit, code 12 means it lit and then lost the flame. Many of the causes overlap.

Check the gas supply and the outside vent first, then reset the unit at the controller.

Common causes

Low gas pressure when several appliances run at once, wind blowing into a poorly placed vent, and buildup on the flame rod are the most common. If resets do not clear it, have the unit serviced.

When to call a technician

Call a licensed technician if code 12 returns after you have checked the gas supply and the outside vent and reset the unit. Testing gas pressure under load, checking vent placement and cleaning or replacing the flame rod are jobs for a professional.