02 Moderate Easy DIY

Rinnai Tankless Water Heater 02 — Power Interruption / Memory Loss

Rinnai Tankless Water Heater · Error code 02

What 02 Means

The unit lost power or experienced a brownout and the control board reset. Often appears after a storm or breaker trip.

Symptoms

  • Unit not responding to demand
  • Code 02 on remote/display
  • Settings reverted to defaults

Common Causes

1
Power interruption

Brief outage or voltage sag reset the PCB.

2
Loose power connection

Plug, hardwire, or terminal block not making solid contact.

3
Tripped breaker

Breaker partially tripped or fluctuating.

4
Failing PCB

Control board losing memory on its own indicates board failure.

How to Fix It

  1. Turn the unit off at the controller and unplug or kill the breaker for 60 seconds.
  2. Restore power and re-set temperature on the remote.
  3. Verify the breaker is fully seated and the outlet/whip is tight.
  4. Check voltage at the unit — should be ~120V AC stable.
  5. If code returns with no outage, replace the PCB.

More Rinnai Tankless Water Heater Codes

03 03 — Loss of Communication / EZConnect Issue 10 10 — Air Supply or Exhaust Blockage 11 11 — No Ignition 12 12 — Flame Failure 14 14 — Thermal Fuse / Overheat Cutoff 16 16 — Outgoing Water Over-Temperature

All Rinnai codes → All tankless water heater codes →

Verified against manufacturer documentation: rinnai.us

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.