Why Is My Tankless Water Heater Turning Off?

A lack of hot water is a major inconvenience to any home throughout Los Angeles and the surrounding areas. It can prevent you from enjoying hot showers and using other hot water fixtures. The culprit may be your tankless water heater shutting off.

As one of the leading tankless water heater experts since 2007, we at Monkey Wrench have seen all the major reasons why a water heater can shut off. By working with the top manufacturers, like Noritz and Navien, we can inspect and diagnose what may have caused your tankless water heater to shut off before we explore different repair options.

There could be various reasons why your tankless water suddenly turned off. Here’s a look at the most common causes.

• Lack of power
• Ignition failure
• Overheated
• The water flow sensor is not working
• Obstructed venting
• Tankless water heater error codes

Once you get through this list, you’ll have a better idea of what caused your tankless water to turn off and why contacting a technician is recommended so you can enjoy hot water access again. 

Why Would a Tankless Water Heater Turn Off?

If your tankless water heater won’t turn on, you’ll have water coming into your hot water fixtures, but it won’t be heated. No matter how long you wait for the water to heat up, it will stay cold until the tankless water heater is inspected and repaired. 

You can visually inspect your tankless water heater, but it’s best to leave the rest to a professional. Once they arrive, they will begin to inspect your tankless unit.

One of the common causes for a tankless water heater shut-off is a lack of power. 

Lack of Power

A tankless water heater can fail to turn on if there’s a lack of power. A lack of natural gas will prevent gas-powered water heating units from using it as fuel for heating. 

Electric-only tankless water heaters will not heat water if there’s a lack of electricity due to an outage, tripped circuit breakers, or loose electrical connections. It may be recommended to upgrade your home’s electrical panel to handle the demands of an electric tankless water heater. 

If your water heater’s gas supply was cut, a technician must apply the necessary measures to reestablish the gas line connection. The gas line supply may also be obstructed, which prevents it from providing the required fuel to begin the combustion process for water heating.

Even if your tankless water heater receives natural gas, it may experience ignition failure, which can cause it to shut down. 

Ignition Failure

Without a working ignition system, a tankless water heater can shut off and be left unable to heat water. Tankless water heaters powered by gas have a burner assembly of various parts that can cause an ignition failure if damaged or defective. 

The igniter provides the spark that creates the flame that heats water, and it may need to be replaced for your tankless water heater to provide hot water. 

Ignition failure can cause your tankless water heater to shut off, but if the system is overheated, it can also turn off.

Overheated

An overheating tankless water heater can shut off and stop your home from having hot water access. As a safety measure to prevent scalding, tankless water heaters have flame sensors and a thermal fuse that can cause them to shut off if the temperature is too hot. 

Limescale buildup from hard water can cause the heat exchanger within the tankless water heater to work harder, causing it to overheat. A water softener can prevent limescale from forming and help extend the lifespan of your tankless water heater. 

Too much heat can cause a tankless water heater to shut off; on the other end, too much water flow may also cause it. 

Too Much Water Flow

If the water demand exceeds a tankless water heater’s capacity, it can be shut off as a precautionary measure. Tankless water heaters are equipped with sensors that register water flow demand. 

A tankless water heater’s capacity is measured in gallons per minute (GPM). If your tankless water heater is designed to handle a specific range of GPM and multiple fixtures are in use simultaneously, the high demand can cause your unit to shut off. 

Besides excessive water flow, issues with your tankless water heater’s venting can also cause it to shut off. 

Obstructed Venting

A tankless water heater can shut off as a safety measure if there are exhaust and air intake issues. Tankless water heaters need oxygen for combustion, so if dirt or debris is blocking the air intake, it can cause it to shut off and not provide hot water.

Gas-powered tankless water heaters need to have their ventilation correctly configured to prevent carbon monoxide from leaking. These units have sensors that can detect if the airflow or exhaust gases are blocked.  

In some cases, these issues can trigger an error code, giving more insight into why your tankless water heater shut down. 

Error Codes

A tankless water heater error code may have been why your unit shut off and stopped providing hot water. Various tankless water heaters issues can trigger an error code. The error code number can vary from manufacturer to manufacturer, whether it’s Noritz, Navien, or Rheem.

It’s highly recommend to call a technician if you see an error code appear on your tankless water. Unplugging and replugging your tankless water heater will not clear the error code permanently. 

How to Address Tankless Water Heater Shut-Off

There are many reasons why your tankless water heater can shut off. Regardless of what it is, it will result in hot water once the issue is resolved. Now that you’ve seen the possible causes for a lack of hot water, you can feel more in the loop about what’s going on with your tankless water heater once a technician arrives to inspect it. 

Our technicians have inspected hundreds of tankless water heaters all over Los Angeles and the surrounding areas and have seen all the possible reasons why they might shut off and not provide any hot water. Thanks to specialized training from some of the top brands in the water heater industry, our technicians are equipped to repair all kinds of tankless water heater issues. 

If you’re dealing with a tankless water heater shut-off issue, contact us using one of the buttons below. As you prepare for a technician visit, check out this article that explains how much a tankless water heater repair may cost.