What does error code 14 mean on a Rinnai tankless water heater?

Thermal fuse or overheat sensor. The thermal fuse or overheat safety sensor tripped.

Can I fix Rinnai code 14 myself?

Start with these safe checks: Turn the heater off and check outside that vent terminals aren't blocked. This is a safety device. A qualified technician needs to find why it tripped before the heater runs again.

When should I call a technician for code 14?

This is a safety device. A qualified technician needs to find why it tripped before the heater runs again. Smell gas? Leave right away, don't touch light switches or phones inside, and call your gas utility or 911 from outside. Never open a gas valve, burner, gas line, vent or flue connection, or bypass a safety switch. Repeated lockouts, scorching, soot, or a CO alarm mean shut it off and call a licensed gas technician.

Rinnai Tankless Water Heater Error Code 14: Thermal fuse or…

What 14 means

The thermal fuse or overheat safety sensor tripped.

Likely causes

Blocked venting or heat exchanger
Wrong gas type setting
Burner problem

Safe first checks

Turn the heater off and check outside that vent terminals aren't blocked.

When to stop

This is a safety device. A qualified technician needs to find why it tripped before the heater runs again.

Checked against: Rinnai: Troubleshooting Tankless Water Heater Diagnostic Codes (100000652). Codes can differ by model and year, so confirm with your owner's manual.