How to Reset a Tankless Water Heater by Brand

The Short Answer: Most tankless heaters reset by turning the unit off and on at the controller, sometimes with a wait or a brief unplug, after you fix the cause the code points to. Rheem’s manual says to wait about five minutes; on Noritz, an ignition-failure code 11 clears when you close and reopen a hot tap or switch the unit off and on. A reset can’t fix a gas, venting or failed-part problem, and some codes, such as a blown thermal fuse, can’t be reset at all.

Before any reset

1. Write down the code and the model number from the rating label on the cabinet.
2. Look the code up for your brand. The owner action, if there is one, is usually what clears it: open a gas valve, refill propane, open a fixture further, clear the vent.
3. Close all hot water taps before restarting.

Rinnai

Rinnai doesn’t publish a general reset procedure. Its manuals give code-specific steps instead. In the Sensei installation and operation manual (opens in a new tab):

• Code 25 (condensate pump accessory): once the pump is plugged in and draining, turn the heater off at the controller, wait five seconds and turn it back on to clear the code.
• Codes 15 and 54: clear the code by resetting the main power supply to the heater.
• Code 03: turn off all hot water taps and press On/Off twice.

For other codes, fix the listed cause and turn the heater off and on at the controller. If the heater still won’t run, the manual’s operating instructions say to turn off the gas to the appliance and call your service technician or gas supplier. See Rinnai code 11, code 12 and code 10. Code 14 means an overheat device opened. Rinnai’s service manual (opens in a new tab) says the bi-metal switch usually resets itself after cooling, while the thermal fuses are one-time devices that must be replaced. See Rinnai code 14.

Rheem and Richmond

Rheem’s RTG manual (opens in a new tab) gives a three-stage sequence. The Richmond-linked edition of the same manual (AP22009 (opens in a new tab), for RMTG models) gives the same steps:

1. Turn off all hot taps. Turn the heater off with the POWER ON/OFF button on the remote, wait about five minutes, turn it back on and open a hot tap.
2. If the code remains, turn the heater off, unplug it for about 30 seconds, plug it back in, carry out the remedy in the code chart, and try again.
3. If the code is still there, note it and call for service. If the code isn’t in the chart at all, turn the heater off and call for service.

Rheem condensing models with a text display, including Richmond’s Encore S and SR, clear stored codes from the menu instead. Manual AP22745 (Rheem copy (opens in a new tab), Richmond-linked copy (opens in a new tab)) has you press SERVICE, then ENTER, choose “Clear Alarms?”, and select Yes. Clearing an alarm doesn’t fix its cause.

Code meanings: Rheem code 11, Rheem tankless error code 12, and Richmond tankless error codes.

Noritz

Noritz manuals pair each code with its own action. For code 11 (ignition failure), the NRC111 owner’s guide (opens in a new tab) says to check that the gas valve is open, press the power button to turn the unit off, open a hot water fixture, and turn the unit back on. The current EZ and NRCR manual (opens in a new tab) adds that the heater resumes when the hot fixture is closed and opened again, or when the power is switched off and on.

Two Noritz codes behave differently:

• Scale codes (C followed by a number, and CF): these warn of scale in the heat exchanger. The NRC111 guide says the unit may shut off and lock; disconnecting power lets it run temporarily, but a “CF” code means it has locked because of repeated scale warnings and the heat exchanger must be flushed.
• Code 14: Noritz’s help center (opens in a new tab) says it can’t be reset because the thermal fuse is physically broken and has to be replaced.

More Noritz detail: Noritz code 11, code 12 and code 29.

Navien, Takagi, A. O. Smith and RV units

• Navien: current NPE-2 models reset with the Back button; older NPE and indoor NPN models have a Reset button (outdoor NPN units reset from the remote). Navien’s manuals say not to unplug the heater except for routine maintenance, because freeze protection needs power. See how to reset a Navien tankless water heater.
• Takagi: see how to reset a Takagi tankless water heater.
• A. O. Smith: see A. O. Smith tankless reset.
• Girard (RV): see Girard tankless reset.

Unplugging in cold weather

Most tankless heaters use electric freeze protection, which matters most for units outdoors or on outside walls. Navien’s manual warns that the freeze protection works only while the cord is plugged in, even with the heater switched off. A brief unplug as part of a reset is fine, but don’t leave a tankless heater without power in freezing weather. See Rinnai tankless water heater frozen for what freeze damage looks like.

When a reset won’t help

• The same code returns right away. The cause is still there. One reset after the owner check is enough.
• Ignition and flame codes keep coming back. Each attempt sends gas through the burner. Have the gas supply, pressure and ignition parts checked.
• Overheat and thermal-fuse codes. Some can’t be reset by design.
• Water is leaking from the cabinet. Turn the heater off and close the cold-water inlet valve before anything else. See tankless water heater leaking from bottom.

For tank heaters, see how to reset a water heater.

Frequently Asked Questions

Q: Is there a reset button on a tankless water heater? A: Some have one: older Navien NPE and NPN models do. Most Rinnai, Rheem and Noritz models reset with the power button on the controller or remote instead.

Q: How long should I wait before turning it back on? A: Follow the brand’s manual. Rheem says about five minutes for its first reset step; Rinnai’s code 25 step uses five seconds. Waiting longer than the manual says doesn’t fix a fault.

Q: Will a reset clear a scale or flush reminder? A: Some reminders can be cleared, but the reminder is there because the heat exchanger needs descaling. Some Noritz models, such as the NRC111, lock out after repeated scale warnings until the heat exchanger is flushed; newer EZ and NRCR models show a C1 descaling reminder.