Stiebel Eltron Tempra High-limit Switch Keeps Tripping

Why Does My Stiebel Eltron Tempra High-limit Switch Keep Tripping?

This is a complete guide on Stiebel Eltron Tempra High-Limit Switch Keeps Tripping. 

From this article, what I am going to break down: 

  • 5 common reasons that cause the unit to keep tripping the high-limit switch
  • How do you reset the Stiebel Eltron Tankless Water Heater?
  • And a lot…

So, keep scrolling. 

Table of Contents

Stiebel Eltron Tempra High-limit Switch Keep Tripping [5 Easy Solutions]

Stiebel Eltron Tempra high-limit switch keeps tripping if the unit receives too much power or the heat exchanger gets clogged by lime buildup. 

Apart from these, the water heater will keep triggering the safety resets due to burnt up heating elements, defective flow sensor, and faulty control board. 

Below, I will take you through every troubleshooting step to discover the culprits behind this issue. Plus, I will show you how to resolve that specific problem. 

1. The Unit Gets Too Much Power

If your Stiebel Eltron Tempra gets too much power than it needs, it will trip the high-limit switch. 

You should check to see what amperage is being supplied to the tankless unit by looking at the number on the breaker. 

The maximum amperage load your Tempra requires to power up the unit can vary depending on its model number. 

At the below chart, I will mention both the maximum amperage load and the circuit breakers size you need to meet the requirements of Tempra: 

Tempra Trend (Models)Max. amp. loadNumber & Min Circuit Breakers Size
Tempra 121 x 50A-1 x 44A1 x 50 A
Tempra 152 x 30A- 2 x 26A2 x 30 A
Tempra 202 x 40A-2 x 35A2 x 40A-2 x 35A
Tempra 24 Plus2 x 50A-2 x 44A2 x 50 A
Tempra 29 Plus3 x 40A-3 x 35A3 x 40A-3 x 35A
Tempra 36 Plus3 x 50A-3 x 44A3 x 50 A

If you choose a breaker size for the unit incorrectly or choose a bigger one, the unit will get more power. And when the unit receives more power, the temperature can turn up to high as well. 

Consequently, the unit will trip the high-limit switch to cut off power to the unit to avoid further damage. 

How To Fix: 

Check the breaker size and ensure you installed the right one. 

Otherwise, you should replace the breaker with the correct one. In this case, you can take a look at the chart I mentioned above. 

However, you can call a certified electrician to wire the water heater correctly if you are not electrically inclined. 

2. Heat Exchanger Gets Clogged

A scale buildup on the heat exchanger can also cause the high-limit switch or the reset button to trigger up.  

You should descale the unit annually or every six months (based on the hardness of the supply water) to avoid the scale from building on the heat exchanger. 

Otherwise, it will cause the unit to overheat the scale to get the temperature high enough. 

As a result, the safety device aka the high-limit switch will pop up to cut the power off to the unit. 

How To Fix: 

Pump a descaling solution through the water heater for about 45 minutes to an hour to remove all the scale buildup. 

If you don’t know how to descale your Stiebel Eltron Tankless Water Heater, you can check out this tutorial: 

It’s super easy. 

3. Heating Element Gets Burnt Up

Many of you may have been encountered this issue: 

“Turn the water off to the unit and leave the unit on. Once you return to your home in about an hour, you find the high-limit safety switch gets tripped and shut the unit off.” 

It occurs because the Stiebel Eltron Tankless unit will continue to put the power to the water heater even after you shut the water supply off to it. In return, it will overheat the heating element and pop up the high-limit switch. 

How To Fix: 

I assume it’s a manufacturer defect. However, Stiebel Eltron Tempra is a wonderful water heater as it’s durable and efficient. 

The easy solution to fix this issue is to turn off both the power and the water supply to the unit when you decide to leave your space. 

4. Issue With Flow Sensor

Flow sensor gets clogged

A defective flow sensor is another culprit that can throw a wrench into work. When this device gets clogged or works intermittently, it can’t sense the presence of water. 

In consequence, the unit will not receive any signal in terms of whether it needs to heat the water or not. 

In the worst case, the unit will keep heating the water, which causes overheating. And when the temperature goes excessively high, it will trip the safety reset buttons. 

How To Fix: 

I recommend you check the flow sensor and ensure it’s working properly. Don’t forget to clear the blockage from the sensor. 

If removing the blockage from the flow sensor doesn’t work, replace it with a new one. 

Fortunately, I already covered an article on Stiebel Eltron Flow Sensor Troubleshooting. Take a look at that article to learn how to clean or replace the flow sensor.

5. Bad Control Board

The control board on the water heater is like a human brain. It controls everything like at what temperature the water will be heated. If it starts malfunctioning, it will receive no signal from the flow sensor. 

As a result, the unit will keep heating the water until it trips the high-limit switch. 

I highly recommend you to hire a certified plumber to have the unit checked professionally. Then, replace the control board if needed. 

How Do I Reset My Stiebel Eltron Tankless Water Heater?

To reset your Stiebel Eltron Tankless Water Heater, follow the following procedure:

  • Turn off every circuit breaker connected to the water heater. 
  • Open the front cover by removing the side screw. 
  • Find and detect the safety thermal cutouts on the top of the copper heating canisters. The buttons at the top are reset buttons. 
  • Press the reset buttons with a pencil with eraser and note whether those buttons make a click or not when depressed. If yes, understand you have reset the unit successfully. 
  • Close the front cover and restore the power to the unit at the circuit breakers. 


What is the lifespan of an electric tankless water heater?

The lifespan of an electric tankless water heater is between 15 to 20 years if you maintain the unit annually. 

Do tankless water heaters have a reset button?

Not every tankless water heater has a reset button. However, the Stiebel Eltron Tankless Water Heater has two reset buttons. 

What happens if you don’t flush your tankless water heater?

If you don’t flush the tankless water heater regularly, it will clog the heat exchangers by scale buildup. As a result, it will overheat the unit and cause the high-limit switch to trip repeatedly. In the worst case, it may even bring ultimate damage to the unit if you don’t flush the water heater. 


The high-limit switch or thermal cutout on the water heater is a safety device. It will cut-off power to the unit when the water temperature keeps rising above the safety range. 

In this case, resetting the thermal safety resets will help you resolve this issue. 

However, if the unit keeps tripping the high-limit switch continuously, there is something going wrong. 

Luckily, I explained all the possible reasons that cause the unit to trigger the high-limit switch. At the same time, I broke down the steps you should take to fix those. 

So, follow the guideline I mentioned and resolve the high-limit switch tripping issue on your Stiebel Eltron Tempra. 

Happy Plumbing!

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