HVACopediaBosch · Boiler · Heating
Heating call, anti-cycle and pump post purge
What happens, in order
- Call for heat from the control or thermostat
- Pump control mode (service function) decides pump behavior: 00 BUS control, 01 pump and burner start together, 03 pump runs continuously, 04 pump only when needed with outdoor reset
- Burner fires and heats to the supply setpoint
- When the supply goes above the setpoint by the switching differential, burner stops
- Fan post purges after the burner shuts off
- Anti-cycle timer blocks a restart for the set time
- Heating zone pump keeps running for the pump post purge time after the call ends
Timings and thresholds
| Item | Value |
|---|---|
| Anti-cycle time (3.b) | 0-15 min, default 3 min, 0 = off |
| Auto anti-cycle (3.A) | default off |
| Switching differential (3.C) | default 18 F (10 C) |
| Fan post purge (5.b) | 10-180 s, default 30 s |
| Heating pump post purge (9.F) | 1-10 min, default 3 min |
Applies to: Greenstar 3A series
Models
More Bosch boiler sequences
- First power-up purge and trap filling · Startup
- Combi comfort and economy modes · Domestic hot water
- Tank priority (ZBR with DHW tank) · Domestic hot water
- Frost protection setup · Freeze protection
- Thermal disinfection of DHW tank · Other
Related
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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.