HVACopediaBosch · Boiler · Domestic hot water
Tank priority (ZBR with DHW tank)
What happens, in order
- DHW tank call comes in while heating is running
- Default is DHW priority tank heats to setpoint first, then boiler goes back to space heating
- Space heating may pause during this and rooms can cool
- Pressing the ECO button switches to alternating operation, where the boiler swaps between heating and DHW
- Tank loading pump runs during DHW mode
Applies to: ZBR heating boiler with DHW tank
Models
More Bosch boiler sequences
- First power-up purge and trap filling · Startup
- Heating call, anti-cycle and pump post purge · Heating
- Combi comfort and economy modes · Domestic hot water
- Frost protection setup · Freeze protection
- Thermal disinfection of DHW tank · Other
Related
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Sequences of operation, error codes and tips work offline in the HVACopedia app.
Source: Bosch Greenstar 6721853955 (2025-11) and 6721853953 (2025-11), Heatronic service functions and operation sections. Written in our own words; timings can differ by model and software version, so check the manual for your exact unit.
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.