Tankless Water Heater Keeps Tripping Breaker – (Fixed)

It’s no fun having cold showers at freezing temperatures, and it’s even more annoying when a tripped breaker causes this experience. But why exactly would a tankless water heater trip the breaker in the first place?

Your tankless hot water heater may trip the breaker if:

  1. You’re using a faulty or undersized breaker
  2. There’s a loose connection in the tankless water heater
  3. You’re using an incorrect wire size
  4. The heating element is exposed.

This article outlines how the water heater interacts with the breaker, how it might trip the breaker, and what you can do to stop your heater from tripping the breaker in the future.

circuit breaker tripped

How Do Breakers Work & Why Are They Important?

Circuit breakers will shut off the tankless water unit when there’s a current overload. It saves you from electrical fire hazards and spending money on a new tankless unit. 

The 1-inch wide 120-volt or 2-inch wide 240-volt circuit breaker is standard in most water heaters. You’ll also find these types of circuit breakers in a host of other household appliances. 

More Reasons Why Your Tankless Water Heater Keeps Tripping Breakers 

Shorted Circuit

A short circuit in the water heater is the most logical cause for a tripping breaker. Short circuits happen when there’s a loose connection in the tankless water heater. Wires connecting the circuit breaker to the unit are prone to short circuits.

Identifying the faulty wire is often tricky as a DIYer since you may not see signs of wear or damage. You’ll see a few burnt wires if you’re lucky, but this is not a foolproof method. If you can’t find the shorted wire yourself, contact a licensed repairer to inspect it.

Faulty Circuit Breaker

This is often the first suspect for most DIYers. Smaller amp circuit breakers can cause overload in the tankless water heater unit. For example, a 4,800-watt unit on a 240-volt line will need a 20-amp circuit breaker. So an 18-amp breaker will continually cause your unit to trip.

It’s better to get a higher amp than the minimum, as this helps your unit handle any electrical strain and last longer. Furthermore, breakers lose their efficiency with prolonged use. 

The Consumer Product Safety Commission (CPSC) reports a lifespan of at least 30 to 40 years for most circuit breakers. You can use a multimeter to test if the breaker is still functional. 

tankless water heater tripping circuit breaker

How Do I Fix or Troubleshoot a Tripping Breaker? 

Breakers for water heaters don’t come cheap. This means your wallet will take a hit every time the circuit breaker blows. Consider the solutions below for fixing a breaker that keeps tripping:

What Do I Need to Fix a Tripping Breaker? 

Most of the necessary materials are in your toolbox. You’ll need:

  • A flashlight to view and fish out bad electrical wires within the unit
  • A multimeter to test the resistivity of the circuit breaker
  • The user manual to identify components.

To troubleshoot the breaker, continue with the following steps:

Step 1: Check nearby appliances

Sometimes, it’s not the water heater unit. Other appliances may also contribute to this problem if they’re connected to the same circuit breaker.

Look at the water heater circuit breaker and trace all wires to see if another appliance is contributing to the load. Is there any appliance overloading the circuit breaker? Remove it and reset the unit to see if it’s functioning normally. 

Step 2: Check the thermostat 

If you are here, it means no appliance is overloading the breaker. So move on to your thermostat. 

It’s often easy to detect a faulty thermostat in tankless heaters. Since thermostats are temperature regulators, a faulty one will overheat the tankless water heater, and the safety device will switch off the unit when the water gets too hot. 

Want to know if the water heater thermostat is the culprit? Use a multimeter to test the resistance level. A functional thermostat will have a reading of less than 1. However, a bad thermostat will have a reading of 1.

Step 3: Check the heating element

Heating elements could be responsible for tripping circuit breakers. Over time, the casing around the element may start to peel off, exposing the internal electrical components to water. As a result, the element will short-circuit and cause the breaker to trip.

The water heater will trip off if the element has a problem. Use a multimeter to verify if the element is faulty and call up a licensed repairer to replace the defective component. 

How to Replace a Circuit Breaker in Tankless Water Heaters 

Switch off all circuit breakers before pulling the main switch to avoid sparking and damage. Then:

  1. Get a flat-tip screwdriver, needle-nosed pliers, and an electrical tester. 
  2. Find the main circuit breaker in your home. You’ll see the numbers 60, 150, or 200 printed on it. Label these breakers before you proceed. 
  3. Identify the faulty breaker and purchase a new one at the local hardware store. Make sure the amp of the new breaker is more than the required minimum. 
  4. Pull out the main meter. The meter has four prongs that fit tightly into the meter box. You may need to apply a bit of force to pull it out, but there are no screws to hold it in place. Pulling it out will shut off all electric appliances in your house. If there’s no main meter, call your electricity company.
  5. Replace the bad breaker with a new one.
  6. Return the meter to the meter box.

Note: The meter box contains live electricity. Do not put your screwdriver or hand into it. Wear rubber soles or stand on a dry wooden board when pulling out the meter. 


Now, you understand the common reasons for why your tankless water heater might keep tripping breakers. Take precautions during this process and call a licensed repairer to handle more technical tasks. As a DIYer, it’s alright to ask for help from trained or professional repairers.