Noritz Tankless Water Heater Won’t Turn On [Why+ How To Fix]

Your Noritz tankless water Heater won’t turn on or keeps shutting off due to the following major culprits:

  • Tripped circuit breaker
  • Insufficient gas supply
  • Power supply Issue
  • Too low flow rate
  • Blocked exhausted

However, first, reset your Noritz water heater to run the unit again.

If the problem isn’t resolved yet, we suspect other villains like dirty flame sensors and clogged heat exchangers are also behind this hit.

noritz tankless water heater won't turn on

Therefore, keep on reading our troubleshooting guide to find out the root reason why your unit isn’t turning on and fix them by yourself.

Table of Contents

Noritz Tankless Water Heater Won’t Turn On [Reasons + Solutions]

In this guide, we’ll walk you through every step so you can solve your Noritz tankless water heater shutting off or not turning on issues. Let’s get started here!

Note: Read our guide on why noritz tankless water heater problems & error codes and how to fix it.

1. Tripped Circuit Breaker

A tripped circuit breaker is the number one reason for not turning your electric water heater. Your water heater’s breaker may trip due to the following factors, For instance

tripped circuit breaker
  • Heater producing excessive temperature
  • Short circuit in the electric lines
  • And, a malfunctioned circuit

When the circuit trips, you won’t turn your Noritz water heater.


Firstly, for a tripped circuit, you can simply flip up the tripped switches to the ON position to turn your unit again. Check out that all the wiring around the electric lines is in good condition. 

Secondly, to troubleshoot the overheating issue, ensure you have set the recommended temperature setting with your water heater. Because overheating can cause the breaker to trip.

But for a short circuit case, we highly recommend you call a certified electrician to deal with the issue. Plus, a clogged heat exchanger is also a major villain behind the problem. So, make sure that the heat exchanger gets clogged.

If this happens, regular flushing is the best solution to prevent overheating issues.

Finally, if your circuit breaker is out of order or broken, replace the circuit breaker ASAP to run your heater properly. 

2. Insufficient Gas Supply

Your Noritz tankless water heater (gas-operated unit) won’t power on if the unit doesn’t get a continuous flow of sufficient gas supply.

Basically, the gas supply will be interrupted during operation unless you turn on the gas valve fully.

noritz tankless water heater insufficient gas supply

On the other hand, improper-sized gas meters prevent your heater from supplying enough gas to the unit. However, this problem isn’t too tough to fix.


To solve the gas supply issue, ensure first, you have paid up your gas bill. And there is sufficient gas in the tank for proper combustion. 

Then, keep the gas supply valve in the ON position and make sure it is fully opened. This supply valve should be parallel to the piping position to supply trouble-free fuel during operation.

Next, don’t forget to inspect the gas pressure. You can read it on the rating plate of the unit. Plus, size up the gas meter accurately to have proper gas pressure.

Otherwise, it will hinder steading free fuel supply to the unit. Let’s know Noritz’s proper gas pressure for a functional water heater.

Noritz Tankless Water Heater Gas Pressure

Type Of Water HeaterRecommended Gas Pressure
Natural Gas Operated UnitBetween 5” W.C. to 10.5” WC
Propane Operated UnitBetween 8” WC to 13.5” WC

If needed, seek help from an expert plumber to inspect gas pressure. This video will be helpful to check the gas pressure.

Lastly, confirm that you have fed the right type of gas for proper combustion. So, ensure either your water heater demands natural gas or propane and then fuel up the right type.

3. Electric Supply Issues

An interrupted electric supply is the next major reason that prevents your Noritz water heater from coming on. A functional electric power panel is a must to run your water heater smoothly.

electric supply issues

As usual, you attempt to turn on the unit by plugging ON but it doesn’t respond to fire up or keeps shutting off. You may experience an unwanted situation if the unit has

  • Power turned off
  • Grounded improperly or loose wiring
  • Improper Circuit panel
  • Non-functional electric unit

If any of the above cases matches your water heater, the breaker will trip and you will never get sufficient electric supply for running the unit.

Typically, the Noritz water heater requires 120 volts at 60 Hz of electric supply for actual operation.

Hence, the unit won’t turn on unless it gets the required power supply. Anyway, now, you need to know how to fix the issue.


First, don’t forget to plug in the wall plug. Ensure the power switch is in the ON position. Just wait for 1-2 minutes to fire up the unit. Basically, the heat exchanger takes a while to heat up.

Then if your water heater doesn’t allow you to turn it on, go for the next troubleshooting procedures.

Secondly, verify the wiring is fine around the electric areas. If you are good at electronically, do it yourself by the followings steps:

  • Remove the junction box with an adjustable screw and open the junction box cover.
  • Attach the ground wire to the ground screw with the cover.
  • Join the power cable to the power cable of the water heater.
  • Be sure, the black and white wire connections are intact to the electric board. 

Additionally, test the voltage of the unit by plugging your phone charger if the outlet is going on fine. 

Next, check out the fuses. If they get damaged, you should replace the blown fuses immediately. 

Finally, confirm that you use an appropriate circuit so that it can consume power up to 360 Hz. Hope the power supply issue will be solved.

Note: If you don’t have enough electricity supply yet, we will highly recommend you hire a certified electrician to resolve your electric troubles.

4. Low Water Flow Rate

A considerable water flow rate is required to activate a tankless water heater. Like every tankless water heater, Noritz has a minimum water flow rate. In this regard, your water heater isn’t an exception to that.

low water flow

Typically, your water heater’s minimum water flow rate is 0.05 GPM for good operation. But, when the flow rate is less than the demand, the unit won’t turn on. Whatever, we have identified several below culprits for the issue. They are:

  • Clogged water drain valves
  • Reverse/cross plumbing
  • The flow sensor gets damaged.


You can simply fix the issue by increasing the water flowing rate. To ensure a minimum flow rate, it is essential to keep the shut-off valve open fully in order to get trouble-free flow.

Next, just open multiple hot water fixtures for passing through the required water flow of the unit.

Next, investigate the water drain valve for blockage. For blockage water drain valves, remove the debris and sediment from the water drain filter to avoid such obstruction.

Plus, take an overview of the flow sensor, if it is damaged or cracked, replace it.

Nonetheless, reverse plumbing can reduce the water flow. For this cross plumbing, verify the hot water and cold water lines are to the point.

Finally, operate your water heater within the reasonable water flow range between 0.5 GPM to 7.5 GMP. It should neither be so high nor too low as per the demand of your heater. Hope you won’t face any issues with the water flow rate further.

5. Malfunctioning Flame Sensor

A flame sensor or flame rod is a device of tankless water heaters that senses the flame to fire up the unit. Normally, your water heater won’t start up if the flame sensor is dirty or damaged.

noritz tankless water heater malfunctioning flame sensor

Over time, the flame can get coated with carbon deposits that prevent the flame sensor from detecting the flame. As a result, your unit remains shut off when it fails to sense the flame.


To troubleshoot the flame, first, try cleaning the rods. To clean it,

  • Switch the power supply of your heater
  • Remove the access front cover to locate it. Inspect any corroded and discolored parts of the flame rods.

Now, take an adjustable Phillip screwdriver to loosen the screws on the side of the unit. Remove the gasket. You should carefully handle the case as the gasket is a very fragile part.

Next, pull out the flame-sensing rod or sensor. Clean the flame sensor rod and ignition plug with a fine-grit sandpaper. And ensure there are no carbon deposits on the probes.

clean the Noritz tankless water heater  flame sensor rod & ignition plug with a fine-grit sandpaper

Anyway, if the flame sensing rods get bent or broken, a replacement will be the best solution to the problems.

6. Scaled/ Clogged Heat Exchanger

A blocked or clogged heat exchanger can be another blame to shut off your Noritz water heater. Because, when the heat exchanger gets clogged by sediments, it leads to overheating your unit. And then, the heater will remain shut off due to the overheating case.


You can simply solve this issue by flushing the heat exchanger. To do so, check out the water quality and sediment that can clog the heat exchanger.

If needed, flush the scaled heat exchanger. Go through the below cleaning procedures to know how to flush a Noritz’s heat exchanger.

How To Flush Noritz Heat Exchanger

Flushing is a regular part of Noritz maintenance. Start your descaling session by turning off the gas valve.

Take your cleaning accessories and complete the following two steps to flush your heat exchanger. You will need:

  • Grade white vinegar (1-2) Gallons
  • 5- Gallon size Bucket
  • Submersible pump3-4″ Hose
  • Drain Connections and screwdriver.  

Step -1:

  • Turn off both the inlet and outlet valves.
  • Attach one drain hose (H1) to the drain valve and one hose (H2) to the circulation pump.
  • Connect the drain hoses H3 and H4.
  • Pour a gallon of calcium and lime-based cleaning solution and mix with a gallon of water in a bucket.
  • Let open both drain valves (V3 and V4). 

Step-2: Clean Heat Exchanger

  • Remove the access front cover from the heater.
  • Attach the blue connector marked FLUSH to get flush on the circuit board.
  • You will get the code CCC on the data display.
  • Turn ON the circulation pump to complete the flushing circulation process.
  • Let it circulate the pump at least for 1 hour at a minimum flow rate of 1.5 GPM.

Next, when it detects the flow of the flushing solution, the display will flash the code C60. But within 60 seconds the code will turn into C59. Next, the code will be changed Coo after an hour. Now, you can keep the circulation pump off.

After completing the steps, remove the drain hoses H1 and H3 and close drain valve-3. But attach the drain hose (H3) into the sink and open the water inlet valve (V1.)

  • Clean the unit with fresh water until it is free from obstructed objects.
  • Close and remove both the drains valves-3 and 4. Detach the (H1) drain hose from drain valve-3.
  • Disconnect the blue connector marked as you attached for “Flushing”

Finally, replace the front cover. Turn the gas supply valve to the ON position and open the water outlet valve.

Note: If the cleaning effort can’t solve your issues, eliminate the trouble by replacing your heat exchanger with a new one.

7. A Blocked Exhaust

Last but not least, a blocked venting system also affects your water heater’s normal operation. When your water heater isn’t working, a blocked vent may be a sign behind the issue.

noritz tankless water heater blocked exhaust

Typically, a tankless water heater needs fresh air to vent outdoors during operation. Hence, it should be free from any blockage. Otherwise, you can’t turn on your heater.


Start your investigation with the exhaust pipe open. Next, check that the vent leading inside and outside are free from any obstruction.

If you can identify any blockage, apply a vent cleaning tool to release the blockage.

While doing this, don’t forget to verify any holes in the pipes and clean the screened debris with a brush. Because it is the main cause to clog your vent system.

And then, inspect whether the plumber has installed the venting system correctly. Because any material can lead to blockage if it is installed too close to other objects.

How To Reset Noritz Tankless Water Heater

When your Noritz water heater goes into trouble with starting on, you can reset your water heater to resolve the issue. It may save you a huge maintenance cost and time. Follow the effective steps to reset the unit.

reset the noritz tankless water heater

Disconnect the power. Locate the reset button. It is usually located on the side or front of the unit.

After getting it, make sure the reset button is in “reset mode.” In this case, you should press the reset button once more to bring it back into reset mode.

  • And then, the light will turn red to green and the burner light should be ON.
  • After the step is done successfully, wait for 10 seconds.
  • Turn on the clockwise knob to the highest setting and wait for 10 seconds again.

Finally, plug the power supply line into the electric outlet.. Now, the reset has been completed and your water heater will work smoothly.

How To Properly Turn On Noritz Tankless Water Heater

You can simply turn on your Noritz water heater by following the steps.

properly turn on noritz tankless water heater
  • Keep the water supply valve to the piping in a parallel sequence.
  • Turn On hot water fixtures to ensure the water is available and then, close it.
  • Open the gas supply valve right to the supply lines.
  • Switch On the power of your heater.
  • Push on the on button and set the temperature 125 F. would be the best setting. Now, open the hot water faucets.

Hopefully, your water heater will turn on for super operation.


Why does my Noritz tankless water heater shut off during the shower?

Your Noritz water heater shuts off during the shower due to low gas pressure or low flow rate. Plus, a defective thermocouple, clogged water line or faulty heating element may be causes for the issue.

Why does my tankless water heater attempt to ignite but fails?

You turn your Noritz heater and it tries to ignite but fails. This may occur if there is air in the gas lines or other valves. Try to reset the unit to fire up your water heater.

What is the normal lifespan of a Noritz tankless water heater?

A normal life span of a Noritz water heater is 12–15 years under warranty. However, with regular maintenance, you can keep your heater in place for another 20 years.


Already, we have discovered that tripped breaker, insufficient gas supply, and low flow rate are mainly responsible for your Noritz tankless water heater not turning on or keep shutting off. 

However, fortunately, we disclosed each of the culprits that will help you to resolve the shutting-off issue.

Now, what you will need, just follow our ultimate troubleshooting steps as mentioned throughout the guide.

And yet, if you encounter any issue to turn on your tankless water heater, let us know by throwing your comments. Our experts will reach out to you ASAP with a simple solution.

About Phillip

Phillip is an HVAC guy & has convenient skills in the fireplace, heater, stove & other heating systems. He has been working and writing in this field for the last 5 years. He is really passionate about writing & share his expertise through his writing to help others. More about us.

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