Why Is My Stiebel Eltron Water Heater Not Working?

Stiebel Eltron Water Heater is not working or heating if: 

• There is no power at the unit
• Insufficient flow rate to activate the water heater
• Restricted flow sensor or it doesn’t spin freely
• Tripped safety thermal cut-out
• Aerator in the faucet or shower head gets clogged
• Water heater not plumbed correctly
• Undersized water heater

You should resolve those issues if you want to bring the water heater back into operating condition. 

And this guide will help you to make your water heater functional again to heat the water. 

So, keep reading till the end. 

Table of Contents

• Stiebel Eltron Water Heater Not Working [7 Solutions]
  • 1. No Power At The Unit
  • 2. Not Enough Flow Rate To Activate The Unit
  • 3. Flow Sensor Gets Clogged or Not Spinning Freely
  • 4. Safety Thermal Cut-Out Gets Tripped
  • 5. Aerator In The Tap Gets Clogged
  • 6. Water Heater Not Plumbed Correctly
  • 7. Undersized Water Heater
• How Do I Reset My Stiebel Eltron Water Heater?
• FAQs
• End-Note

Stiebel Eltron Water Heater Not Working [7 Solutions]

This chapter will explain everything that causes the unit to not work or heat the water at all. Plus, I will provide the solution to those issues that prevent the unit from heating. 

1. No Power At The Unit

The Stiebel Eltron Tankless Water Heater won’t heat the water if the unit gets no power at the unit. 

Generally, the unit will not receive any power if the circuit breakers connected to the water heater are off. 

How To Fix: 

Go to your circuit breaker box or panel. 

Then, inspect all the circuit breakers attached to your water heater. If they are in Off position, flip them up to On. 

If you still don’t get any power at the unit after turning on every circuit breaker to the water heater, there is a problem with your home’s electrical wiring. 

In this case, you should call a certified electrician to have the home’s wiring checked professionally. 

2. Not Enough Flow Rate To Activate The Unit

Every water heater has a minimum water flow rate to activate the unit. And Stiebel Eltron Tankless Water Heater is not an exception to that. 

For example, Stiebel Eltron Tempra 24 Plus has required a minimum water flow of 0.5 GPM to get this unit activated. 

If the water flow doesn’t meet this requirement, the water heater will not work or heat the water. 

The water flow at the unit generally gets interrupted due to the following reasons: 

• Filter screen gets clogged by debris or scale buildup
• Restricted faucet aerator or shower head
• Set the water flow too low

How To Fix: 

To begin with, check the filter screen first and ensure it’s free of debris. Otherwise, you should clean the filter screen. 

In order to clean the filter screen, you should have the following kits at your fingertips, including: 

• Needle-nose pliers
• An adjustable wrench
• A plastic bucket
• A rag

Once you gather all these pieces of equipment, turn off the power to the unit at the circuit breaker. 

Then, close both the hot and cold water ball valves on the unit. 

Afterward, place the plastic bucket under the cold side fittings to minimize water spills.

Next, remove the braided steel hose from the cold side connection using the adjustable wrench. 

Now, it’s time to take the filter screen off. Regarding this, use the needle-nose pliers to remove the filter screen from the cold water inlet. 

Lastly, wash the filter screen under running water in the sink. If there is still debris on the filter screen, use a brush to brush away the remaining debris.

After cleaning the filter screen, re-insert it into the cold water inlet and screw up the braided steel hose to the cold side connection. Then, tighten up the connection using the adjustable wrench. 

If cleaning the filter screen doesn’t bring any luck, check the faucet aerator or the shower head. Don’t hesitate to clean the aerator if needed. 

And last not the least, sometimes you will experience reduced water flow if you set it too low. 

In this case, you should increase the water flow so that the requirement can be met. To increase the water flow, turn the flow adjustment screw counterclockwise. 

3. Flow Sensor Gets Clogged or Not Spinning Freely

As I mentioned earlier, the water heater will not work if the minimum water flow doesn’t flow through the unit. 

And a clogged flow sensor will also interrupt the water supply to the unit. The flow sensor generally gets restricted by debris and scale buildup. 

How To Fix: 

I recommend you replace the flow sensor instead of freeing up the blockage from the flow sensor. And the below tutorial will help you in replacing that sensor: 

4. Safety Thermal Cut-Out Gets Tripped

Stiebel Eltron Water Heater has a safety device called safety thermal cutout or reset buttons. 

If the unit heats the water excessively, the unit will trip the safety thermal cutout to cut off power to the water heater. 

As a result, your Stiebel Eltron Tankless Water Heater won’t work or stop heating the water. 

How To Fix: 

Resetting those safety reset buttons will be a must if the safety thermal cutout has been triggered. 

To reset the safety thermal cutout or reset buttons, turn off the power to the unit at the circuit breaker. 

Then, unscrew the front cover and locate the reset buttons. You can find the safety resets on the top of the copper heating vessels. 

Once you find those reset buttons, press the safety resets using a pencil with eraser. If the reset button clicks when depressed with pencil, the reset button has been reset successfully. 

Lastly, close the front cover and secure it and restore the power to the unit by turning on all the circuit breakers to the unit. 

5. Aerator In The Tap Gets Clogged

Sometimes a clogged aerator in the faucet or shower head can cause the water heater to not work by reducing the water flow. 

How To Fix:

You can easily solve this problem by cleaning the aerator in the faucet or the shower head. 

If you don’t know how to clean the aerator in the tap or the shower head, the follow tutorial will come handy: 

6. Water Heater Not Plumbed Correctly

Incorrectly plumbing the water heater will also cause the unit to not work or heat the water at all. 

For example, if you plumb the cold water pipe into the hot outlet or the reverse, you will get no hot water out of the unit. 

How To Fix: 

Check the plumbing connection and fix it. Ensure the cold water enters on the right side and the hot water outlet exists on the left side. 

7. Undersized Water Heater

If you don’t size up the water heater according to your demand, the unit will stop working or heating the water. 

You can easily avoid this issue if you consult with a plumber before choosing a water heater. 

How Do I Reset My Stiebel Eltron Water Heater?

The following procedure will help you reset your Stiebel Eltron Water Heater:

• Turn off all circuit breakers connected to the water heater.
• Open the front cover by unscrewing the nut that keeps the front cover in place.
• Locate the safety thermal cutouts on the top of the copper heating canisters. The buttons at the top are the reset button. 
• Press those buttons with a pencil with an eraser. If you hear a click when depressed the button with the pencil, understand the reset buttons have been reset. 
• Close the front cover and restore the power to the unit by turning on all the circuit breakers. 

FAQs

What causes a water heater to need to be reset?

When the water heater trips the reset button or thermal safety cutout due to overheating, you need to reset the unit by pressing the reset button. However, if your water heater keeps tripping the safety cutout repeatedly, you should replace the reset button itself.

Can a tankless water heater get clogged?

Yes, a tankless water heater gets clogged by deposits buildup in the heat exchanger. 

If you don’t flush the unit regularly like once a year or twice a year, the scale contained in the supply water forms a lime formation. Overtime, this scale buildup clogs the heat exchanger. 

And too low water pressure from a hot water faucet is an indication that indicates your water heater gets clogged by deposits.

What is the lifespan of an electric tankless water heater?

The total lifespan of an electric tankless water heater can be between 15 to 20 years with proper yearly maintenance.

End-Note

I described all the possible reasons that can cause your Stiebel Eltron Water Heater to not work. 

All you need to do now is just troubleshoot your water heater by following the troubleshooting steps I mentioned. 

I hope you can resolve the issue and make your water heater ready to heat the water.

Good Luck!

Read Also:

• Stiebel Eltron Tankless Water Heater Troubleshooting