How to Reset a Tankless Water Heater

Published onMarch 10, 2024
How-to Guides

Whether it’s from a power outage, inconsistent water heating, or continuous error codes, knowing how to reset a tankless water heater can be a quick and easy way to restore your endless hot water supply. In this guide, we’ll provide step-by-step instructions on how to reset tankless water heaters from brands like Rinnai, Navien, Rheem, and Noritz.

Table of Contents

Why Would a Tankless Water Heater Need to be Reset?

Tankless water heaters are great because they give you an endless supply of hot water whenever you need it without taking up a lot of space. However, like any appliance, they’re not immune to the occasional hiccup.

Let’s look at some of the most common reasons why you might need to reset your tankless water heater:

You recently had a power outage
You aren’t getting any hot water
You’re experiencing inconsistent water heating
The system overheating
To reset any programmable thermostat settings
To clear any error codes
Electrical problems

Most tankless water heaters flash error codes to let you know when there are problems within the unit. However, you’ll also get them if your gas pressure needs to be adjusted or if there’s something obstructing the vent.

While resetting your tankless may not fix every problem, it’s a good first step you can take to determine if there’s a larger issue going on that would require professional help.

Let’s start by going over how to reset a Rinnai tankless water heater.

How to Reset a Rinnai Tankless Water Heater

Rinnai tankless water heaters don’t have a reset button, so you’ll have to do this manually. The steps for resetting a Rinnai tankless water heater will vary depending on whether you have an indoor or outdoor model.

How to Reset an Interior Rinnai Tankless Water Heater

Step 1: Unplug the tankless from the outlet.

Step 2: Wait 10-15 seconds.

Step 3: Plug the unit back in and wait a few minutes. During this time, the unit will start its restart process.

Step 4: Once finished, turn the hot water on at a fixture.

How to Reset an Exterior Rinnai Tankless Water Heater

Step 1: Locate the on/off switch next to the tankless.

Step 2: Open the cover and flip the switch to the off position.

Step 3: Wait 10-15 seconds and switch the unit back on.

Step 4: Turn the hot water on at a fixture and make sure the tankless is working.

Note: Once you plug your unit in or turn the switch back on, you’ll begin to hear noises that closely resemble the way dial-up internet used to sound when starting. This is normal. Just wait a few minutes for it to go through its startup cycle.

You can also reset your Rinnai water heater by turning the electricity off at your circuit breaker. To do this, find the breaker that corresponds to your Rinnai water heater and turn it off. Wait 20-30 seconds, and then turn the breaker back on.

There may also be times when you’ll need to reset your Rinnai back to its factory settings. This is typically done to clear any error codes or after any maintenance that’s been done like flushing your tankless.

How to Reset a Rinnai Tankless Water Heater Back to Factory Settings

To reset a Rinnai tankless water heater back to its factory settings, you can follow these steps:

Step 1: As a safety measure, turn off the electricity to your tankless water heater.

Step 2: Unscrew and remove the cover.

Step 3: Once the cover is removed, locate the PC board on the bottom right of the unit.

Step 4: Find the two black A and B buttons on the PC board.

Step 5: Press and hold these buttons for 5-10 seconds until you see a “P” displayed on the control panel. Once displayed, release the buttons.

Step 6: Press and hold the two buttons again until “PCL” is displayed. Once displayed, release the buttons, and your Rinnai will begin the reset process.

Step 7: Once the reset process completes, go to a fixture and cut on the hot water to make sure the system is working as it should.

How to Reset a Navien Tankless Water Heater

To reset a Navien tankless water heater, follow these steps:

Step 1: Locate the reset button on the front display panel. On newer models, this will be the button with the return arrow on it.

Step 2: Press and hold the reset button for 5-10 seconds or until you hear a beep. This indicates that the reset process has started.

Step 3: Allow the unit to go through its reset process.

Step 4: Check to make sure your temperature settings are the same.

How to Reset a Rheem Tankless Water Heater

To reset a Rheem tankless water heater, follow these steps:

Step 1: Turn the gas valve to the off position.

Step 2: Turn the incoming water line to the off position.

Step 3: Turn the electricity off to the unit.

Step 4: Unscrew the four screws on the front panel cover and remove it.

Step 5: Locate the PC board inside your Rheem tankless. It will be located toward the bottom left of the unit.

Step 6: Look for the two sets of dip switches and the two buttons underneath that say min and max.

Step 7: On the set of switches labeled “DIP switch 1”, move switch 2 up and down within 5 seconds.

Step 8: Immediately after you flip this switch up and down, press and hold both the min and max buttons for at least 7 seconds. On the display screen, you should see a “UL” code flashing.

Step 9: Hold these buttons until the “UL” code turns solid or disappears.

Step 10: Once you see a solid “UL” code or it disappears, press the power button to turn your Rheem tankless back on. Once on, you should see the temperature showing on the display screen.

Step 11: Turn the gas, electricity, and water valves back on. Run hot water at a fixture to make sure everything is working as normal.

How to Reset a Noritz Tankless Water Heater

Resetting a Noritz tankless water heater is a very simple process. All you need to do is disconnect the power and turn it on again. This should clear any codes that are present.

Once you reset a Noritz tankless water heater or if you lose power to the unit, you may need to reset the temperature setting and the flow meter alarm.

Final Thoughts

By following the steps above, you should now be able to reset your Rinnai, Navien, Rheem, or Noritz tankless water heater when common issues come up.

If resetting doesn’t solve the problem, you may need to have a licensed technician come out to take a look. Or, if you’re considering an upgrade anyway, check out our guide on how to choose a tankless water heater for insights into selecting the right model for your home.