Navien Tankless Water Heater Keeps Tripping Breaker [Solved]

You’re in the middle of a hot shower and suddenly your water heater stops working. Annoyed at the situation, you go and see that the breaker is tripped. To make matters worse, it keeps on happening. So, why does the Navien tankless water heater keep tripping the breaker?

From my personal experience of working on many Navien water heaters, I have identified the five main reasons behind it. They are:

  • Faulty GFCI outlet.
  • Leaking water.
  • Incorrect wiring or ground.
  • Electrical issues.
  • Using wrong parts.
navien tankless water heater keeps tripping breaker

Keep on reading to find out more about these issues and their solutions in detail. You’ll also learn how you can replace a faulty breaker on your own. So, let’s dive in!

It’s not very common for Navien tankless water heaters to trip circuit breakers. That’s because they’re normally connected by GFCI power outlets instead of directly to the breaker.

Electrical water heaters are prone to tripping the breaker when they have a damaged heating element, a faulty thermostat, or loose wiring connections. However, it can also happen in a tankless water heater in a few cases. I’ll talk about the main reasons behind it in this section.

01. Faulty GFCI Outlet

Most Navien water heaters are connected to a GFCI outlet. If your unit seems to start well but soon after that it gets interrupted, the first potential culprit is a malfunctioning GFCI outlet.

GFCI outlet of navien tankless water heater

Thankfully, you can easily inspect this on your own. All you need to do the test is an extension cord. Connect the plug of the water heater to another GFCI outlet using the extension cord. If the water heater works now, the issue has always been with the GFCI outlet.

How To Fix:

You’d have to replace the GFCI outlet if the previous one was faulty and the Navien heater kept tripping it. Thankfully, it’s an easy job for someone who is electrically inclined. As I’ve done it multiple times in my career, I’ll show you how to do it. You can follow these steps to replace the outlet:

  1. Cut off the power supply to the GFCI outlet by turning it off at the main circuit breaker. Undo the screws holding the cover plate in place and remove it.
  2. Remove the screws holding the inner outlet in place and pull it to the outside. But don’t pull it too hard as it’ll be connected to wires. Double-check that there is no power to the outlet by using your tester.
  3. Loosen the screws on the side of the outlet and then, you’ll disconnect it from the wires. You can completely remove the outlet now and throw it away.
  4. Put the wires into the line side of the new GFCI outlet. First, connect the ground wire around the wire in a clockwise motion. The white or neutral wire will go on the silver screw. As for the black or hot wire, it’ll go on the golden screw.
  5. Fold the wires back into the box and push the new outlet against the wall. Tighten the screws to secure its place and reconnect the front panel of the outlet. Reattach the screws until everything is nice and tight and turn on the power supply at the circuit breaker.

That’s how easy it is to replace the GFCI outlet on your own. It really is a simple process. But don’t worry, you can hire an electrician for this job if you don’t feel comfortable doing it yourself. Make sure the new GFCI outlet is working properly after you’ve replaced it.

02. Leaking Water

Another common culprit behind tripping the breaker is when the water leaks inside the water heater. The water leak can fall on the wiring connections and easily shorten something out.

leaking Water of navien tankless water heater

The main reason behind this is the ignorance of DIYers. For example, I know of someone who got water inside the unit while replacing the flow sensor. The water that leaked inside wreaked havoc on the system and the circuit breaker at the GFCI outlet got tripped.

How To Fix:

First things first, you’d have to clean the wet parts of the water heater. Use a blow dryer to dry all the water in that area. Then, see if that solves the issue. If the problem still remains, it could be due to a shorted wiring connection. You’ll learn how to solve that in the next section.

03. Incorrect Wiring Or Ground Connection

If the water leaks on the wiring connections, they could be damaged. That could lead to tripping the breaker. Check the connections and see if any of them are loose as well.

Not having good ground can also cause this issue. Check the ground between the ground wire and the heater case using a multimeter. If you’re confused about which one is the ground wire, look for the green wire.

The control panel may get in the way and block your view. But now that you know what you’re looking for, you should be able to find it easily.

How To Fix:

If the wiring connections are damaged, you need to replace the wires. The same goes for the ground wires. You have to establish that all the wires are working fine. Take the help of an electrician to rule out any wiring issues.

04. Electrical Issues

If the unit trips the breaker at the breaker box, it’s possible that the problem is not with your water heater but with the breaker. If you’ve gone through the other reasons and none of them seem to be a problem, this could be it.

Unplug the water heater from the power outlet and turn it back on. If the breaker trips on its own after a while, then the problem is with the breaker rather than the heater.

How To Fix:

If the breaker keeps tripping on its own due to any reason, it has to be replaced. You can do it yourself if you have expertise in dealing with electronic components. Since I know how to do it, I am showing you how to do it.

How To Replace Circuit Breaker Of Navien Tankless Water Heater?

You’ll need the replacement breaker, a pair of needle nose pliers, a flathead screwdriver, and a roll of painter’s tape to complete this replacement job. Once you have these tools, you can follow these steps:

Step 01 – Turn Off The Main Breaker

Locate the main breaker panel in your house and take a picture of it so that you don’t mess anything up when you put it back together later on.

Identify the breaker you want to replace and flip it to the “Off” position. Better yet, you can turn off the main breaker and cut off the power supply to your entire house if possible to be extra safe.

Keep in mind that the breaker will always have live power even if you turn it off as the power comes from the big wires on top. So, don’t be careless and touch the wires as you do the replacement job.

Step 02 – Remove The Faulty Breaker

Remove the screws holding the front cover of the breaker in place and remove it. The cover is heavy and it won’t stay in position once you remove the final screw. So, be prepared to carry its weight the moment you remove the last screw.

Have a flashlight ready if you’re working in an area that doesn’t get any daylight. Mark the breaker you want to replace with the painter’s tape so that you don’t lose track of it later on.

Loosen the screw at the end of the breaker which you want to replace. You’ll be able to pull out the wire once it becomes loose and separate it from the breaker.

You may be surprised to know this but the breaker isn’t connected by any more screws. You can just grab it by the edge and pull it out. If the breaker you want to replace is on the right side, pull it to the left. Similarly, pull the breaker to the right if it’s placed on the left side.

removed circuit breaker of navien tankless water heater

Step 03 – Install The New Breaker

Now it’s time to put the new breaker in place. If you try to push it straight in, it won’t go into position. You’d have to insert it at an angle like shown in the picture below so that it can get in and snap into the right place:

inserting circuit breaker at an angle of navien tankless water heater

Then, push the opposite end of the breaker and it’ll be in the right position. There’s no way to install a breaker incorrectly. So, if you feel that it has snapped in place, you’ve done the job right.

Next, connect the wire to the newly attached breaker. If the screw of the breaker is tight, you need to loosen it. Make sure the wire goes between the two small plates of the screw. Hold on to the wire when you tighten the screw so that it doesn’t pop out and makes a good connection.

The final thing is to put the cover back on. They can be pretty heavy, so make sure you can handle the weight. You may have to wiggle the cover a little so that it locks into the right place. Then, you can tighten the screw and complete the installation.

That’s how easy it is to replace the circuit breaker. Remember that you should only do it if you have worked with such electronic parts before. Otherwise, you’d be better off hiring a qualified technician to do this job.

05. Using Wrong Parts

Another reason why the Navien water heater trips the breaker is that the right parts aren’t being used. For example, the wiring in the breaker or using the breaker of the wrong size can cause it to overload. If it’s happening in a new installation, there’s a strong possibility that this is the case.

How To Fix:

If you’re using the wiring or the breaker of the wrong size, it’s actually good news because you can easily replace them and solve the issue. Match the current parts of the requirement of your water heater and change them if they do not match. Hopefully, that’ll solve the tripping issue.

How To Know If A GFCI Outlet Is Working Correctly?

You already know about the easiest way of testing the GFCI outlet of your water heater. You can use an extension cord to plug the heater into another GFCI outlet. If the heater works now, the first outlet was bad.

But if you don’t have an extension cord available, there are other ways to test the outlet. First of all, you can unplug the heater and connect a simple device to that outlet. For example, you can see if your phone charges via that outlet. If it does, it means the outlet is fine. Otherwise, it’s bad.

You’ll also notice two buttons on your GFCI outlet. Each and every GFCI outlet should have these buttons. One of them says “Test” and the other one says “Reset”. When you press the test button, the reset button should pop up.

test & reset button of GFCI

You can do the test right now and see if the reset button comes up when you push the test button. If it does, the GFCI outlet is working like it should. If it doesn’t, that’s a sign that you have a bad outlet. The only solution in such cases is to replace it and you already know how to do it.


How long does a GFCI outlet last on average?

GFCI outlets are actually supposed to last for a long time and they last somewhere between 15-25 years on average. Once that period has passed, you should replace them.

Can the circuit breakers fail on their own?

Yes, it’s not a huge shocker that circuit breakers can fail by themselves without any fault of other electrical equipment. Some of them are damaged from the get-go and they can also go bad due to high humidity or voltage spikes.

How to keep the GFCI outlets from tripping?

The tripping of the GFCI outlet is a safety feature that protects the other electronic components from being damaged. So, you shouldn’t think about bypassing the mechanism. Instead, press the test button from time to time and see if it’s working properly.

What is the cost to replace a GFCI outlet?

The outlet itself only costs between $10-$25. But you may have to pay upwards of $100-$150 in labor charges. So, you should replace the GFCI outlet on your own if you know how to do it.


Now, you know the main reasons why the Navien tankless water heater keeps tripping the breaker and how to fix this issue. Be patient while you diagnose the issue and keep your cool.

Hopefully, the tripping problem is caused by a simple problem and you’ll be able to fix it easily. If you want to get more use out of your water heater, check out my guide on how to maintain a Navien tankless water heater.

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