Stiebel Eltron heat pump water heater
Stiebel Eltron Accelera 220 E / 300 E (earlier manual edition) error codes
Covers: Accelera 220 E / Accelera 300 E (earlier manual edition linked as 'Use & Care Manual', file install-accelera-220-e.pdf)
Every code listed in Stiebel Eltron's own manual for this series, with what it means and what Stiebel Eltron says to do. Last checked 2026-10-03.
Is this your model? An earlier edition of the Accelera 220 E / 300 E manual. Its fault code menu 2 lists only E2 and E64, with different wording from the current manuals. Stiebel Eltron's documents don't say which heaters each edition applies to, so check both if your code isn't listed.
| Code | Label | What the manual says it means |
|---|---|---|
| 0 | No fault | |
| 2 | The dome sensor has failed. The temperature displayed is measured by the integral sensor. The appliance will continue to work properly but the amount of mixed water will read as less than 2 gallons. | |
| 4 | The integral sensor has failed. The mixed water display will not show the correct amount but the appliance will continue to work properly. | |
| 6 | Dome sensor and integral sensor failed. The appliance stops heat delivery. | |
| 8 | The appliance has recognized that the DHW tank is not heated for 13 hours, despite there being a demand. | |
| 16 | Short circuit impressed current anode / protective anode failed | |
| 32 | Either: The appliance is operating with an empty tank or the appliance is not delivering heat. Or: The anode current is interrupted. The appliance does not heat up. | |
| 128 | No communication between controller and display. The most recently selected set values are active. | |
| 256 | Manually activated Emergency backup mode (only electric booster element active). | |
| E2 | Defrost sensor has failed. | |
| E64 | Temperature of the evaporator is less than -4°F. May be due to low air flow or a fan issue. |
Combined codes
When more than one fault is active, the display adds the codes together; in emergency backup mode it adds 256 more. These are the combined codes the manual lists. (Operation and Installation - Accelera 220 E / 300 E (linked as 'Use & Care Manual'), A 312097-40208-9260, page 18)
| Display | Made up of |
|---|---|
| 8 | 8 (one fault on its own) |
| 264 | 8 (one fault on its own) (emergency backup mode on) |
| 10 | 8 + 2 |
| 266 | 8 + 2 (emergency backup mode on) |
| 12 | 8 + 4 |
| 268 | 8 + 4 (emergency backup mode on) |
| 24 | 16 + 8 |
| 280 | 16 + 8 (emergency backup mode on) |
| 26 | 16 + 8 + 2 |
| 282 | 16 + 8 + 2 (emergency backup mode on) |
| 28 | 16 + 8 + 4 |
| 284 | 16 + 8 + 4 (emergency backup mode on) |
| 138 | 128 + 8 + 2 |
| 394 | 128 + 8 + 2 (emergency backup mode on) |
| 140 | 128 + 8 + 4 |
| 396 | 128 + 8 + 4 (emergency backup mode on) |
| 152 | 128 + 16 + 8 |
| 408 | 128 + 16 + 8 (emergency backup mode on) |
| 154 | 128 + 16 + 8 + 2 |
| 410 | 128 + 16 + 8 + 2 (emergency backup mode on) |
| 156 | 128 + 16 + 8 + 4 |
| 412 | 128 + 16 + 8 + 4 (emergency backup mode on) |
Safety first
- WARNING Electrocution: Do not insert objects through the grille into the interior of the appliance. Never spray the appliance with water. Never spray water into the appliance. (pg. 15)
- WARNING Injury: Maintenance work, such as checking the electrical safety, must only be carried out by a qualified contractor. (pg. 15)
- Emergency shutdown: interrupt the power supply; shut off the cold water supply; immediately notify a qualified contractor, as the appliance is not protected against corrosion while the power supply is interrupted; drain the tank if there is a power outage longer than 2 days. (pg. 15)
- WARNING Injury: The evaporator consists of numerous sharp-edged fins; wear protective clothing, especially safety gloves. (pg. 28)
From the manufacturer's manual for this series.
Troubleshooting without a code
No hot water is available.
Likely cause: No 220-240 V power to the appliance.
What to do: Check that the appliance is connected to the 220-240 V power supply.
No hot water is available.
Likely cause: The circuit breaker in the electric panel has tripped.
What to do: Check whether the circuit breaker in the electrical panel has tripped. If required, disconnect the appliance from the power supply and replace the circuit breaker. Contact your contractor if the circuit breaker blows again after the appliance is connected to the power supply.
No hot water is available.
Likely cause: The air intake or air discharge of the appliance is blocked.
What to do: Check the air intake grille and air discharge grille for contamination. Remove any contamination. Check thermostat setting.
No hot water is available.
Likely cause: The ambient temperature exceeds the upper application limit. The appliance safety equipment has responded and the appliance has switched off automatically.
What to do: Wait for the appliance to cool down. Call a qualified contractor if the appliance does not switch back on automatically.
No hot water is available.
Likely cause: The ambient temperature falls below the lower application limit. The evaporator is currently being defrosted.
What to do: Wait until the appliance switches back on automatically.
The appliance is not heating the DHW tank although the heat pump symbol is illuminated.
Likely cause: The blocking time for compressor has not yet elapsed. Once the compressor has been switched off, it will only be switched back on again after the 20 minute compressor blocking time has elapsed.
What to do: No action required.
The safety valve of the cold water supply line is dripping.
Likely cause: These units are under water mains pressure. During the heat-up process, expansion water will drip from the safety valve. Ensure that adequate expansion volume was installed in the DHW loop.
What to do: Notify a qualified contractor if water continues to drip when heating is completed. Check the sealing of the P&T valve if a sand filter is used. If expansion volume is too small, install a larger expansion tank.
The condensate drain drips.
Likely cause: The surface temperature of the evaporator is lower than the dew point temperature of the ambient air. Condensate forms.
What to do: The amount of condensate depends on the air humidity level.
The room temperature drops too low.
Likely cause: Due to the heat pump process the room temperature drops.
What to do: The temperature drop depends on the hot water demand and the size of the installation room. If the temperature drop of the installation room is more than 7 °F (4 °C) check the size of the installation room.
Service symbol is continuously illuminated.
Likely cause: See 7.1, "Fault codes".
What to do: Notify a qualified contractor.
Service symbol flashes and the water does not heat up.
Likely cause: See 7.1, "Fault codes".
What to do: It is imperative that you notify a qualified contractor.
The heat pump symbol is illuminated but the compressor is not running. The fan is running.
Likely cause: The appliance is in defrost mode.
What to do: No action required.
The "heat pump" symbol is flashing.
Likely cause: There is a demand for heat, but the compressor is blocked from starting.
What to do: No action required. The compressor is blocked for 20 minutes from starting again after it has been switched off in normal operation. The compressor switches itself on automatically after the 20 minute blocking time has elapsed. The symbol stops flashing automatically.
The "electric emergency/booster heater" symbol is flashing.
Likely cause: A temperature controller has switched off the "electric emergency/booster heater" during rapid heat-up.
What to do: No action required. The appliance continues the rapid heat-up process using the heat pump. The symbol stops flashing when the controller releases the "electric emergency/booster heater". The symbol goes out when the temperature throughout the DHW cylinder reaches the set temperature of 149 °F (65 °C).
The appliance switches off unexpectedly and does not switch on again. (installer section of the manual)
Likely cause: Excessive pressure in the refrigerant circuit. The safety pressure limiter has responded. The compressor has been switched off.
What to do: Eliminate the cause of the increase in pressure in the refrigerant circuit. Wait approx. 5 to 15 minutes for the appliance to equalize the pressure. Reset the safety pressure limiter.
The appliance switches off unexpectedly and does not switch on again. (installer section of the manual)
Likely cause: The appliance is operated outside the operation limit. The ambient temperature is higher than the permissible value. The safety pressure limiter has responded.
What to do: Ensure that the operation limit is observed. Wait approx. 5 to 15 minutes for the appliance to equalize the pressure. Reset the safety pressure limiter.
The compressor switches off unexpectedly. (installer section of the manual)
Likely cause: The thermal load of the compressor has been exceeded. The motor overload relay has responded.
What to do: Remedy the cause of the high thermal load. Wait until the appliance restarts.
The appliance generates less heat. (installer section of the manual)
Likely cause: An inadequate air flow across the evaporator may be a possible cause.
What to do: Check whether the fan is contaminated. Check whether the evaporator is contaminated. Ensure that supply and extract air flow are unimpeded.
Owner maintenance
casing
Use a damp cloth to clean the casing sections. Never use abrasive or corrosive cleaning agents.
clean air intake grille / air discharge grille
How often: every six months
Clean the air intake grille and air discharge grille every six months. Cobwebs or other kinds of contamination can restrict the air supply to the appliance.
anode (DHW tank)
How often: maintenance-free
The DHW tank is equipped with a maintenance-free impressed current anode to safeguard against corrosion. The power supply must not be interrupted while the appliance is filled with water to enable the impressed current anode to provide protection. Otherwise there is a risk of corrosion.
descale electric booster element
How often: from time to time
Have the electric booster element descaled from time to time. This will extend the expected life of the electric booster element.
safety assembly and evaporator check
How often: regularly
Have the safety assembly and the evaporator checked regularly by a qualified contractor.
condensate drain
Undo the condensate drain. Check that the condensate drain is clear and remove any dirt from the condensate drain connection of the appliance.
clean evaporator (installer section)
How often: checked for contamination and corrosion and cleaned as necessary
Remove the control panel and the appliance cover. Carefully clean the evaporator fins. Use water and a soft brush for this. Never use acidic or alkaline cleaning agents.
drain tank (installer section)
How often: e.g. when shutting the appliance down; always if no hot water usage for a long period
Unplug the appliance from the power supply. Close the shut-off valve in the cold water supply line. Open the drain valve installed in the cold water supply line (if none installed, undo the cold water supply line at the "cold water inlet" connection). Open one tap in one sink. Some residual water will remain in the lower section of the DHW tank.
descale electric booster element (installer section)
Only descale the flange of the electric booster element after removing it, and never treat the interior of the DHW tank and the impressed current anode with descaling agents.
protective anode fault (installer section)
How often: if a fault code indicates the protective anode is faulty
Remove the controller of the electric booster element. Check the protective anode connector and its wiring. Refit the controller of the electric booster element.
valves (installer section)
How often: regularly
Check all valves in the system (safety valve, pressure reducing valve, drain valve, vacuum breaker, mixing valve) and remove lime-scale deposits. Replace the valves if necessary. Check the function of the valves.
air filter
Stiebel Eltron's product page says: "Because the evaporator is self-cleaning no filter is required."
Sources
- Operation and Installation - Accelera 220 E / 300 E (linked as 'Use & Care Manual') (A 312097-40208-9260)