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FlowMax · Boiler · Heating

Heating call with restart delay and pump overrun

FLOWMAX 90/120

What happens, in order

  1. Thermostat calls for heat in WINTER or SUMMER/WINTER mode
  2. Burner ignites and modulates to the heating setpoint
  3. When the call ends the burner stops and the fan does a post-ventilation run
  4. Heating pump keeps running for the overrun time (standard 3 min, or permanent if parameter 4 = 01)
  5. Heating timer blocks a new heating start until it expires, which prevents rapid on/off cycling
  6. Water hammer prevention (parameter 5) can be switched on or off
  7. Changes to parameters only take effect after switching the unit off and on

Timings and thresholds

ItemValue
Heating restart timer (param 6)00-90 steps of 5 s, default 36 = 180 s
Heating pump overrun (param 7)00-90 steps of 5 s, default 36 = 180 s
Pump mode during heating (param 4)00 standard 3 min overrun, 01 permanent
Water hammer prevention (param 5)00 off, 01 on (2 s)

Codes you may see during this

E05 E01 E35 E16 E42

Applies to: FLOWMAX-120

Models

FLOWMAX-120

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Source: FLOWMAX-120 installation manual (DIGITECH PCB SM20021, parameters 4-8, function codes 07/08/28). 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.