Stiebel Eltron · Accelera 220 E / 300 E (earlier manual edition)
Stiebel Eltron Accelera 220 E / 300 E (earlier manual edition) error code 256
What it means
Manually activated Emergency backup mode (only electric booster element active).
How it shows: Service (wrench) symbol flashing
What Stiebel Eltron says to do
See 5.5.2, "Emergency back up mode", pg. 15.
Last checked 2026-10-03.
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)
From the manufacturer's manual for this series.
The same code on other models
Codes mean different things on different heaters. Match the series to the model number on your rating label.