HVACopediaBosch · Boiler
DHW setpoint flashing Set DHW temperature flashing on display
What the display is showing
After the DHW thermostat is turned, the chosen DHW temperature blinks on the display for half a minute and then the display returns to the supply temperature.
Applies to: Greenstar ZBR/ZWB 21-42-3A wall-hung boilers and ZWB 28-42-3A combis
Models that show this code
4 models in Bosch Greenstar
Other codes on the same units
- A.b Service function A.b - DHW temperature
- Ad DHW tank temperature not detected
- C.d Service function C.d - current heat demand
- CC Outdoor temperature sensor not recognised
- Display off Display dark - appliance switched off
- EA No flame detected
- ECO button lit ECO button lit - economy / alternating mode
- Emissions test button Emissions test (chimney sweep) button
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Source: Bosch Greenstar wall ZBR-ZWB 21-42-3A service 6721853955 (2025-11) (same content in combi service 6721853953), 8.10 / 8.11 p.55. Summarized in our own words; check the original manual for your model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.