Stiebel Eltron Tankless Water Heater Troubleshooting

This is a complete guide on Stiebel Eltron Tankless Water Heater Troubleshooting. From this article, what you are going to learn: 

• The common problems of Stiebel Eltron Tempra Plus
• Problems you will encounter with the Stiebel Eltron DHC Tankless Unit
• Issues with the Stiebel Eltron DCE Premium Tankless Water Heater
• How to reset the Stiebel Eltron Tankless Water Heater

Without further ado, let’s dive in.

Table of Contents

• Stiebel Eltron Tankless Water Heater Troubleshooting [The Ultimate Guide]
  • Stiebel Eltron Tempra Plus Troubleshooting 
    • No Hot Water
    • Restricted Hot Water Flow
    • Water Not Hot Enough 
  • Stiebel Eltron Tempra Plus Error Codes
  • Stiebel Eltron DHC Tankless Water Heater Troubleshooting
    • No Hot Water But Audible Click Can Be Heard  
    • No Hot Water And No Audible Click 
    • Water Not Warm Enough 
  • Stiebel Eltron DCE Premium Tankless Water Heater Troubleshooting 
    • Unit Won’t Start Despite The DHW Valve Is being Fully Open
    • When the hot water is being drawn off, cold water flows for a short period 
    • Boiling Noises Are Heard During Operation
    • The Required Temperature Can’t Be Set 
  • Stiebel Eltron DCE Premium Diagnostic Light Codes
• How Do I Reset My Stiebel Eltron Tankless Water Heater? 
• End-Note

Stiebel Eltron Tankless Water Heater Troubleshooting [The Ultimate Guide]

You will find every solution to a specific problem regardless of the water heater you own from Stiebel Eltron like the Tempra Plus, DHC, and DCE Premium.  

Stiebel Eltron Tempra Plus Troubleshooting

No matter what model of Tempra you own, this chapter will reveal the common problems of Stiebel Eltron Tempra Plus. Plus, you will get the solution to each of the issues.

No Hot Water

No hot water will be produced by your Stiebel Eltron Tempra due to the following reasons: 

• Circuit breakers to the water heater are off.
• Insufficient flow rate to activate the unit
• A clogged flow sensor or this part is not spinning freely
• You or your installer may fail to plumb the water heater correctly

How To Fix: 

Your Stiebel Eltron Tempra will not get any power if the circuit breakers to this unit are off. And when it gets no power, how can you expect the heater to heat the water? 

To fix this issue, go to your circuit breaker box and ensure you turn on all the circuit breakers to the water heater. 

Secondly, every tankless water heater has a minimum activation flow rate. 

If the water flow rate doesn’t meet that requirement, the unit will not turn on. The flow rate for water heater’s activation can vary based on the models. 

Take a look at the following chart to see the minimum water flow to activate the unit: 

Tempra Trend (Models)	Min. Water Flow
Tempra 12 Trend	0.37 gpm
Tempra 15 Trend	0.5 gpm
Tempra 20 Trend	0.5 gpm
Tempra 24 Trend Plus	0.5 gpm
Tempra 29 Trend Plus	0.77 gpm
Tempra 36 Trend Plus	0.77 gpm

Generally, you will not get enough water flow rate to activate the unit if the filter screen or the faucet aerator gets clogged by sediment buildup. 

In other words, you need to clean either the filter screen or the shower head if you are experiencing reduced water flow. 

To clean the dirty filter screen, follow the below cleaning procedure: 

• Turn off and lock all the circuit breakers to the unit.
• Close the hot and cold water ball valves on the unit.
• Place a bucket under the cold side fitting to minimize spills.
• Unscrew the braided steel hose by using an adjustable wrench from the cold side connection. 
• Remove the filter screen using needle nose pliers.
• Rinse debris from the filter screen. Use a brush to clean away any remaining debris. 
• Reinsert the filter screen back into the cold water connection. 
• Replace and tighten the cold water connection hose.
• Reopen the cold and hot water ball valves.
• Remove the circuit breaker locks and turn on every circuit breaker connected to the water heater. 

Thirdly, inspect the flow sensor and ensure it doesn’t get restricted or spin freely. 

Fortunately, I published an article on Stiebel Eltron Flow Sensor Troubleshooting. Check that article to learn what you need to know if the flow sensor gets clogged. 

And last not the least, you should plumb the water heater correctly. Make sure the cold water enters on the right side and the hot outlet exists on the left. 

Restricted Hot Water Flow

You will get insufficient hot water flow at the faucet because of either a clogged filter screen or scale buildup on the heating elements. 

How To Fix:

To get sufficient hot water flow, you should inspect and clean both the filter screen and the heating elements. 

Luckily, I have already mentioned the way of cleaning the filter screen above. 

When it comes to descaling the heating elements, I recommend you hand over this task to a professional as it requires a lot of elbow grease. 

Water Not Hot Enough

The Tempra Tankless Unit will heat the water insufficiently due to the following reasons: 

• Water flow rate is too high
• The unit is receiving too low voltage
• The thermal safety cutout gets tripped

How To Fix: 

If the water flow rate is too high, reduce the water flow. You should keep reducing the water flow until the power light on the front cover stops blinking. 

Secondly, ensure the unit is getting sufficient voltage to activate the unit. The voltage your Tempra unit requires should be between 208V and 240V. 

And finally, check the thermal safety switches and ensure they don’t get tripped. 

To access those buttons, open the front cover and locate the thermal safety switches on the top of the copper heating canisters. 

Then, press the switches with a non-conductive element like a pencil with eraser. 

Take a note whether those buttons click or not when pressed. If yes, understand you reset them correctly.

Stiebel Eltron Tempra Plus Error Codes

The Tempra Plus can throw these error codes that will help you diagnose and resolve the problem: 

Error Code	Cause	Solution
2	Inlet temperature sensor failure	Check the inlet temperature sensor and replace it if needed. Or, you can call a certified technician for help.
3	Outlet temperature sensor failure	Ensure the outlet temperature sensor cable is attached to the main control boardReplace the sensor if required

Stiebel Eltron DHC Tankless Water Heater Troubleshooting

This chapter will help you resolve the problems of any models of Stiebel Eltron DHC Tankless Unit you own. 

No Hot Water But Audible Click Can Be Heard

You won’t get hot water though you can still hear the audible click from the unit because of the following reasons: 

• Circuit breaker off
• Safety thermal cut-out has tripped
• Undersized water heater 

How To Fix: 

Before doing anything else, check the circuit breaker first. If you forget to turn on all the circuit breakers connected to the unit, the water heater will not receive any power. 

Just open the circuit breaker panel and flip up all the circuit breakers for the water heater to On position. 

2ndly, tripped safety thermal cut-out buttons can also cause the unit to not heat the water. To fix this issue, just reset the thermal cut-out switches. 

And finally, size up the water heater according to your usage demand. 

I recommend you to not turn on other appliances like the washer when using the water heater. It will help reduce the pressure on the unit.

No Hot Water And No Audible Click

This issue actually occurs when the water flow gets too low to activate the flow switch. 

Generally, too low water flow is the result of a clogged faucet aerator, not opening the shut-off valve fully, and setting the flow rate too low. 

How To Fix: 

First off, check the faucet aerator for restriction and clean the aerator if needed to let the water flow freely. 

Next, ensure you open the shut-off valve completely. 

And lastly, ensure you set the flow rate at the optimal level. To increase the flow rate, open the flow adjustment screw by turning counterclockwise.

Water Not Warm Enough

The water heater will deliver lukewarm water if you set the water flow too high or the unit receives insufficient voltage. 

How To Fix: 

Reduce the water flow if it goes out of specification or you set it too high. 

To reduce the water flow, close the flow adjustment screw by turning clockwise. It will help increase the water temperature by decreasing water volume.

Next, ensure the water heater receives a sufficient amount of electricity for proper operation. 

Otherwise, you should call a certified electrician if the unit doesn’t get the minimum voltage it requires to turn on. 

Stiebel Eltron DCE Premium Tankless Water Heater Troubleshooting

This chapter will be applicable for the owners who own the Stiebel DCE Premium. 

Unit Won’t Start Despite The DHW Valve Is being Fully Open

This problem will occur if:

• There is no power at the unit
• The aerator in the tap or the shower head gets dirty or clogged up
• The water supply gets interrupted

How To Fix: 

You will get no power at the water heater if the circuit breakers connected to the unit are off. So, open the circuit breaker panel and ensure you turn on all the breakers to your hot water heater. 

Turns out, the DCE Premium tankless unit from Stiebel Eltron won’t turn on if the aerator in the top or the shower head gets scaled up. 

To resolve this issue, just take a look at the aerator in the tap or the shower head and clean it if required. 

Nonetheless, the water supply to the unit gets interrupted if you fail to vent the unit or the cold water inlet line properly. 

I recommend you call a professional to vent the water heater correctly. 

When the hot water is being drawn off, cold water flows for a short period

You will encounter this issue with your DCE Premium Tankless Water Heater when the air detector detects air in the water. It will switch off the heating output briefly. 

However, it’s not a problem at all as the unit restarts automatically after 1 minute. In other words, you don’t need to take any corrective actions. 

So, don’t worry. 

Boiling Noises Are Heard During Operation

The boiling noise will come from the unit during operation if the unit is not vented properly. Apart from this, too low supply pressure can cause the unit to create the boiling noises. 

How To Fix: 

Vent the water heater properly to stop the boiling noise. 

During initial start-up, you must engage the AE3 safety switch before supplying power to the unit. Otherwise, the unit won’t turn on until the safety switch has been engaged. 

That’s why you should open and close all connected draw-off valves for at least 15 minutes during initial start-up. Also, you should purge all the air from the pipework and the water heater by letting the water run for 3 minutes.

Lastly, check the supply pressure and increase it if needed. 

This unit requires a minimum of 26.1 PSI supply pressure for activation. Of course, the supply pressure shouldn’t exceed more than 145 PSI. 

The Required Temperature Can’t Be Set

Stiebel Eltron DCE Premium Tankless Water Heater has an internal anti-scalding protection system. 

If this system gets activated, you can’t set the required temperature. 

I recommend you to not adjust the internal anti-scalding protection system by yourself. It will be better to let the certified technician handle this task for you. 

Stiebel Eltron DCE Premium Diagnostic Light Codes

Take a look at the following charts and discover the meaning of the diagnostic light codes: 

Diagnostic Lights	Meaning	Causes	Corrective Actions
No LED is lit	The water heater does not heat up	No power at th unitBad PCB	Ensure you turn on all the circuit breakers to the unit Replace the PCB
Green flashing, yellow off, red off	No DHW	The aerator in the tap or the shower head gets cloggedThe filter screen in the cold water inlet gets dirtyThe flow meter is not plugged inDefective flow meterBad PCB	Clean or replace the aerator Clean the filter screen Connect the flow meter wiring to the PCB Replace the flow meter Replace the bad PCB with a new one
Green flashing, yellow on, red off	The display on the programming unit is off	The cable between the PCB and the programming unit comes looseThe cable of the programming unit gets defectiveFaulty programming unit PCBFaulty PCB	Check the cable and plug it into the programming unit or the PCB. Replace the cable Replace the programming unit PCB. Replace the PCB
Green flashing, yellow on, red off	The outlet temperature does not match the set value	The programming unit wasn’t plugged in before the power was switched onFaulty outlet sensorFaulty tapDefective heating systemBad PCBFaulty motorized valve	Perform a reset by turning off the power to the unit. Replace the outlet sensor. Replace the bad tap with a new one. Replace the heating system. Replace the pCB. Replace the motorized valve.
Green flashing, yellow off, red on	No DHW	Air detected	Continue draw-off for more than a minute
Green flashing, yellow off, red on	Wrench flashes (displays E1 and wrench in menu “Fault code display”)Wrench flashes (displays E2 and wrench in menu “Fault code display”)Wrench flashes (displays E3 and wrench in menu “Fault code display”)	AE3 safety switch not engaged during commissioningAE3 safety switch gets triggeredDefective high-limit safety cut-out switchBad PCBShort circuit in outlet sensor	Activate the AE3 Safety Switch by pressing the reset button. Check the high-limit safety cut-out switch and activate the AE3 Safety Switch. Replace the high-limit safety cut-out switch. Replace the PCB. Inspect the outlet sensor and replace it if needed

How Do I Reset My Stiebel Eltron Tankless Water Heater?

What procedure you need to follow to reset the Stiebel Eltron Tankless Water Heater:

• Turn off every circuit breaker connected to the water heater.
• Open the front cover of the unit.
• Locate the safety thermal cutouts on the top of the copper heating canisters. The buttons at the top are reset buttons.
• Press those reset buttons with a non-conductive element like a pencil with eraser.
• If you hear a clicking noise while depressing the buttons, understand you reset the unit correctly. 

End-Note

Throughout this Stiebel Eltron Troubleshooting Manual, I mentioned every common problem you may or will encounter with your tankless unit. 

Just follow the troubleshooting steps I described and resolve the issue. 

However, if you fail to resolve a problem by following this guideline, don’t forget to reach out to the Stiebel Eltron Technical Support at 800-582-8423. 

Best of Luck!

Read Also:

• Stiebel Eltron Water Heater Not Working
• Stiebel Eltron Tankless Water Heater Reset Button