HVACopediaFlowMax · Boiler · Freeze protection
Heating and DHW frost protection
What happens, in order
- Works while the unit has power and the gas valve is open, even with the ON/OFF switch at OFF
- Heating circuit when the heating sensor reads 5 C the unit fires at minimum gas pressure with the 3-way valve in winter (heating) position
- Heating circuit protection stops when the heating sensor reaches 30 C
- DHW storage circuit when the sensor reads 4 C the unit fires at minimum pressure with the 3-way valve in summer (DHW) position
- DHW protection stops when the storage cylinder sensor reaches 8 C
- Display shows function code 08 while frost protection is active
Timings and thresholds
| Item | Value |
|---|---|
| Heating circuit start | 5 C |
| Heating circuit stop | 30 C |
| DHW storage start | 4 C |
| DHW storage stop | 8 C |
Applies to: FLOWMAX-90, FLOWMAX-120
Models
More FlowMax boiler sequences
- Switch-on and mode selection · Startup
- Heating call with restart delay and pump overrun · Heating
- DHW call with pump overrun and priority · Domestic hot water
- Switched OFF at the control panel · Standby/shutdown
- Flue test and legionella functions · Other
Related
Take it to the job
Sequences of operation, error codes and tips work offline in the HVACopedia app.
Source: FLOWMAX-120 installation manual (DIGITECH PCB SM20021, parameters 4-8, function codes 07/08/28); FLOWMAX-90 user manual (control panel, start-up, diagnostics). 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.