03 — Rinnai Tankless Water Heater Code 03 — Power Interruption During Bath Fill
Power was interrupted while the unit was running a Bath Fill operation. When power returns, water will not flow again until the unit is reset.
- Keep using it?
- Yes — fix when convenient
- DIY difficulty
- Easy
- Verified against
- media.rinnai.us ↗
How to fix it
- Turn off all hot water fixtures.
- Press the ON/OFF button on the controller twice to reset the unit.
- Confirm normal water flow and operation after the reset.
Why it happens
Typical signs: Code 03 displayed after a power interruption during a Bath Fill cycle · No water flow from the unit until it's reset · Occurs after a brief outage or breaker trip mid-fill
- Power interruption during Bath Fill A brief outage, voltage sag, or breaker trip while the unit was executing a Bath Fill cycle leaves the control logic in a state where it won't flow water until reset.
More Rinnai tankless water heater codes
Frequently asked questions
What does the 03 code mean on a Rinnai tankless water heater?
Power was interrupted while the unit was running a Bath Fill operation. When power returns, water will not flow again until the unit is reset.
What causes the 03 code on a Rinnai tankless water heater?
Power interruption during Bath Fill: A brief outage, voltage sag, or breaker trip while the unit was executing a Bath Fill cycle leaves the control logic in a state where it won't flow water until reset.
Is it safe to keep using a Rinnai tankless water heater with a 03 error?
Yes — fix when convenient. This is rated a minor-severity fault.
How do I fix 03 on a Rinnai tankless water heater?
Turn off all hot water fixtures. Press the ON/OFF button on the controller twice to reset the unit. Confirm normal water flow and operation after the reset.
Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: media.rinnai.us.