EcoSmart Tankless Water Heater Troubleshooting

EcoSmart Tankless Water Heater Troubleshooting

This guide on EcoSmart Tankless Water Heater Troubleshooting will break down common tankless water heater problems, including: 

  • Water heater is not heating at all
  • Water temperature or the unit is not getting hot
  • Water temperature at the faucet is less than the set temperature

Turns out, I will explain the meaning of the common error codes your EcoSmart Tankless Water Heater will throw. 

Nonetheless, I will walk through additional troubleshooting tips like how to check electric connection or check the heating elements. 

Lastly,  I will also show you how to reset a EcoSmart Tankless Water Heater to operate the unit temporarily until you fix a specific problem. 

Indeed, it’s a complete guide which will help you resolve the issue your EcoSmart unit is going through. 

So, let’s dive in. 

Table of Contents

EcoSmart Tankless Water Heater Troubleshooting [Ultimate Guide]

This chapter will explain the common water heater problems your EcoSmart Unit is going through. 

Water Heater Is Not Heating At All

Water is flowing through the unit but the unit doesn’t heat the water at all. If this is the problem you are experience, the followings are to blame, including: 

  • The unit gets no power or your plumber wires the unit incorrectly.
  • Flow rate is too low
  • Internal part failure

How To Fix: 

To fix the no heating issue of your water heater, you can check this guide I wrote on EcoSmart Tankless Water Heater Not Heating

In that article, I explained every troubleshooting tips to resolve the no-heating problem. 

Water Temperature or The Unit Is Not Getting Hot Enough

The unit won’t heat the water sufficiently due to the following reasons: 

  • Bad heating elements
  • Water flow is too high
  • Crossed wires
  • Voltage less than 240V
  • Mixing too much cold water

How To Fix: 

All the issues that cause the water temperature to not get hot have been already covered in this article: EcoSmart Water Heater Not Getting Hot

So, check the article and discover the solution to make your water heater ready to heat the water again. 

Water Temperature At The Faucet Is Less Than The Set Temperature

Most water faucets now have anti-scald features. It automatically mixes cold water even when you turn the control lever or handle to fully hot. 

As a result, the water temperature you get at the faucet is less than the temperature you set on the unit. 

Nonetheless, thermal loss due to long pipe runs is another culprit behind this issue. 

How To Fix:

Faucets with anti-scald features are adjustable. It means you can adjust those devices. So, adjust the faucet so that you can turn off the cold mix. 

On the other hand, you should increase the water temperature on your water heater if you lose heat due to thermal loss. You can even resolve this issue by insulating the pipe.

EcoSmart Tankless Water Heater Error Codes

Over time, your tankless water heater will throw one of the following error codes. 

You should know the meaning of those fault codes, which will make the diagnostic process easy. 

And below, I explained the meaning of each error message. 

Error Code E1

Defective inlet thermistor is what causes the error code E1. It means the inlet thermistor is not reading the temperature correctly and you need to replace this part to fix this issue. 

If you want to fix this issue temporarily until the replacement part ships at your door, you can reset the unit to bypass this error code. 

Error Code E2

If the digital display of your unit is throwing the error code E2, understand the outlet thermistor is at fault. 

It notifies you that the outlet thermistor fails to read the correct temperature. In other words, you need to replace the outlet thermistor to erase this error code permanently. 

However, you can fix this issue temporarily by resetting your EcoSmart Tankless Water Heater. 

Error Code E3

When both the inlet and the outlet thermistor fails to read the water temperature correctly, the unit will pop up the error code E3.  

To resolve this issue, you must replace both the inlet and the outlet thermistors. 

As it’s not possible to get the replacement parts readily at all times, you can bypass this error code for a short term solution. 

And the solution is to reset your EcoSmart Water Heater. 

Error Code E4

The temperature of incoming water is rising over 150 or higher, which causes your EcoSmart Water Heater to throw the error code E4. 

The tankless unit is equipped with 2 to 4 thermostats rated 140F. And you already know no water heater is not rated to heat past 140F. 

To fix this issue, just lower the incoming water temperature under 140F. 

Once the water temperature is getting lower under 150, the LED display will illuminate with desired set temperature. 

If you fail to resolve this issue, you can call the support team at (877) 474-4673 or send an email at

Error Code E5

High flow rate is what causes your EcoSmart Tankless Water Heater to flash the error code E5.  

And the easy solution to this issue is to slow down the flow rate. Each shower, sink, and faucet comes with an aerator to control the volume of water. 

And each of them has a certain flow rate, like: 

  • Sinks: 1 – 2.5 GPM (gallons per min)  
  • Showers: 1.5 – 3 GPM  
  • Bathtubs : 3.5 – 8 GPM  
  • Washing machines: 1.5 – 2.5 GPM

Now, the question that spins around your head is- how can I determine the water flow that flows through a certain system? 


Just go along with the following procedure to see the what flow rate is flowing through a certain system: 

  • Press and hold down the round button for 10 seconds to get to the diagnostic screen.
  • In the diagnostic menu, three screens are navigable . In this case, you need to rotate the round knob counterclockwise. First, you can see the inlet water temp. 
  • First turn of the round knob will display the outlet water temp. 
  • Second turn of the round knob will show you the current flow rate. 

I have already mentioned the remedy to erase the error code E5. Just slow down the flow rate and walk away. 

To do so, it’s highly recommended to install a flow restrictor or close the incoming or the outgoing water valve slightly. 

Error Code S103

The error code S103 indicates your water heater is not receiving the correct power to turn on the unit. 

This water heater requires a minimum voltage of 240V to function correctly. I highly recommend you to hire a certified electrician to check the electrical connections. 

Additional Troubleshooting Tips For EcoSmart Tankless Water Heater

Here I will walk you through every troubleshooting step to check the thermistors, the flow meter, the electrical connection, the fuse, and the heating elements. 

Thermistors Troubleshooting

Each EcoSmart Tankless Water Heater is equipped with two thermistors- one on the inlet side (yellow wire) and the other one on the outlet side (red wire).  

The purpose or function of these devices is to measure both the incoming and the outgoing temperature. 

More importantly, it will keep the temperature 1 or 2 degrees (+ or -) of the set temperature shown on the digital display. 

When these thermistors fail to work properly, the control board will not send any power to the heating elements.  

To test the thermistors, follow the below steps: 

EcoSmart Water Heater Thermistors troubleshooting
*Checking Thermistors*

1. Turn off the breaker for the water heater to shut off the electric supply to the unit. 

2. Take the front cover out by unscrewing the four screws that you can find on the top and on the bottom of the unit. 

3. Locate the plastic cover that covers the control board. It’s secured by four screws- one in each corner. Unscrew those screws and remove the plastic cover. 

4. Locate the thermistors on the control board and remove them: 

  • Disconnect both the inlet and the outlet thermistors from the control board.
  • Both wires are plug & play style. 
  • The inlet thermistor wire is yellow and the outlet thermistor wire is red. Just unplug them from the control board. 

5. Turn the circuit breaker for the unit back to the on position while leaving the thermistors disconnected. 

6. Now, run a hot water tap at a sink for approximately 3 to 4 minutes. Within this period, the unit will start to heat the water. 

7. If the water heater starts to begin heat with thermistors unplugged, understand the thermistors are defective. In other words, you need to replace them to get hot water out of your water heater. 

Flow Meter Troubleshooting

Flow meter troubleshooting
*Flow meter troubleshooting*

On the inlet side of your tankless unit, you can locate the flow meter. It has a small propeller that must spin free counterclockwise to activate the heater. 

This device senses water flow and controls the activity of the unit by doing so. 

If the flow meter works properly, the LED will illuminate and stay illuminated when water is flowing through the system. 

On the other hand, if the LED display doesn’t stay illuminated while running water, walk through the following steps:

1. The first step is to clean the flow meter by running a high volume of water heater through the system. 

  • Turn on at least 5 to 6 GPM for at least 3 minutes. In this case, you can open the bathtub, shower, and a sink. 
  • Take a look at the LED display and ensure it’s illuminated once you have a high volume of water running through the system. 
  • Slow down the GPM’s if the LED display gets illuminated with water flow. Close all the running water faucets or taps except for 1 sink to verify the unit is heating and the LED is staying on. 

2. If the LED display is not staying on with water flow, you need to remove it and rinse it out.

  • Locate the flow meter, unscrew it, remove the impeller and clean it with running water.
  • Place every part back into place and make sure the impeller is spinning freely
  • Open a few faucets and run water for approximately 3 to 4 minutes. It will flush the water lines and remove the air pockets. 
  • Restore the power to the unit and ensure the LED display remains illuminated. It will take up to 45 to 50 seconds for the unit to heat the water. If this doesn’t fix the issue, you must replace the flow meter. 

Checking & Verifying Electrical Connection

Checking Electrical connection on EcoSmart Tankless Water Heater

Models 18 to 36 Kilowatts come with a 4-6 prong terminal block (depending on model) marked- Circuit Breaker A (L1 L2), Circuit Breaker B (L1 L2), Circuit Breaker C (L1 L2), and Circuit Breaker D (L1 L2). 

Every circuit set must be attached to an independent double pole 40 amp breaker. 

Ensure the set of wires from each leg are not crossed at the breakers. Otherwise, you water heater won’t function as designed.  

To ensure the wiring is attached correctly, perform the below test: 

  • Detach all the circuit breakers at the service panel. Once you disconnect all the breakers, measure the voltage going to each one of the sets. All are should read 0.
  • Turn on 1 breaker. It doesn’t matter which one you set to the on position. 
  • Use your voltmeter and place one probe on L1 and the other one on L1. Measure across and you should get a reading of 208 to 240V. Repeat the same for other breakers as well. 
  • If you measure the voltage across one of the legs in a set the voltage in another leg of another set, your wires at the breakers are crossed. And you must fix this. 

I highly recommend you perform this test on all legs of the terminal block both at the bottom and the top of the terminal block by turning on 1 breaker at a time. 

If the power going to your water heater is not correct, the unit won’t work properly. It means there is no problem with the unit. Indeed, there is a problem at the breakers or at the electrical panel. 

In this case, you must hire a certified electrician to solve the electrical issues. 

Checking The Fuse

EcoSmart Tankless Water Heater comes with one inline fuse. It is specially designed to protect the control board against power surge. 

Based on the heater you own, the unit has one of two fuses. Go along with the following steps to locate and test the fuse electrically: 

Fuse A /250 Volt 3 AMP 

Checking the fuse 1
  • Start by turning the breaker off for the water heater. 
  • Remove the front cover by unscrewing the four screws. 
  • Locate the white plastic housing of the control board and remove it.
  • On top of the housing, you can find the round black fuse holder and open it.
  • Insert new fuse (250V 3 Amp) and put the holder back together.
  • Now, restore the power to the unit and ensure the unit is turning on. 

Fuse B/250 volts 500 milliamps Fast Acting

Checking the fuse 2
  • Turn the breaker off
  • Remove the round knob.
  • Unscrew the four screws that hold the plastic cover on the LED display controller.
  • Locate the fuse on the upper right hand corner of the board.
  • Install new fuse (250V-200-400 mA)
  • Turn the breaker back to the on position and verify if the unit is turning on or not. 

Checking Heating Elements

Checking heating elements on EcoSmart Water Heater
*Checking heating elements on EcoSmart Water Heater*

Follow the below step-by-step procedure to check the heating elements: 

  • Remove the front cover.
  • You can find two wires connected to the top of the heating element. To check whether the element is functioning correctly or not, you should turn on a hot water faucet. This will help both elements to draw voltage and you can check them electrically. 
  • Once the water is flowing through the unit, the LED display will light up and show the temperature setting on the display. 
  • Use your voltmeter and place one probe on one screw and the other one to another screw located on the top of the heating element. 
  • You will get the voltage reading between 208V to 240V while measuring across the top of the elements. 
  • If your LED display is illuminated and the water is running through the system, you should have 0 voltage reading. 
  • Now, it’s time to perform the conductivity test. In this case, set the voltmeter to Ohm setting. Place one probe on one screw and the other probe on the other screw of the top of the element. 
  • A healthy heating element should give reading between 6 to 10 Ohms. Otherwise, you should replace the heating element. 

How To Reset EcoSmart Tankless Water Heater?

EcoSmart Tankless Water Heater has a reset button on the controller. It will help you reset the button with a single click. 

To reset the unit, just go along with the following steps: 

  • Turn on your water heater so that the display comes on and read a specific error code it shows.
  • Press and hold down the round knob for at least 3 to 5 seconds and release the button. 
  • At this point, the display should be reading CE1. 
  • Keep water running for 2 to 3 minutes and check for hot waters. 

Note: When your water heater is running in the CE1 mode, the unit will heat the water at 125 degrees. In this mode, you will no longer control the outlet temperature. Besides, you should mix some cold water to reach your desired temperature setting. 


A malfunctioning tankless water heater is a pain in the neck, especially in the cold days of winter. 

Fortunately, this guide on EcoSmart Tankless Water Heater Troubleshooting will make it easy for you to determine a specific problem. Also, I broke down what steps you should take to fix that problem. 

What you need to do is- navigate through each troubleshooting step, detect the issue, and resolve that issue. 

Good Luck! 

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