FlowMax · Boiler · Startup

Switch-on and mode selection

FLOWMAX 90/120

What happens, in order

Open the gas isolation valve under the unit
Set the ON/OFF switch to ON
Check the display for flashing codes; H2O means no water or low pressure, fill the system to at least 1 bar and it restarts by itself
In WINTER mode with a room thermostat connected, the unit lights automatically on a heating call
SUMMER mode heating circuit locked out, burner lights only for a domestic hot water call; symbol flashes while burning
WINTER mode burner lights only for a heating call (domestic hot water off)
SUMMER/WINTER mode burner lights for either heating or DHW calls
If a fault stops the unit and it will not restart, unplug for 30 seconds, plug in and try the ON/OFF switch again

Timings and thresholds

Item	Value
Heating temperature range	30-80 C (low temp 25-59 C)
DHW temperature range	35-60 C
Minimum system pressure	1 bar
Power reset wait	30 s

Codes you may see during this

H2O E01

Applies to: FLOWMAX-90, FLOWMAX-120

Models

FLOWMAX-90FLOWMAX-120

More FlowMax boiler sequences

Heating call with restart delay and pump overrun · Heating
DHW call with pump overrun and priority · Domestic hot water
Heating and DHW frost protection · Freeze protection
Switched OFF at the control panel · Standby/shutdown
Flue test and legionella functions · Other

FlowMax error codes · FlowMax tips · All FlowMax sequences

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Sequences of operation, error codes and tips work offline in the HVACopedia app.

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Source: 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.