FlowMax Error Code H2O: Low water pressure in heating circuit (Combi Boiler)
FlowMax error code H2O on a combi boiler means: Low water pressure in heating circuit. It is also called FlowMax diagnostic code H2O.
Homeowner? What FlowMax code H2O means for you
Check, then call Your combi boiler is reporting: Low water pressure in heating circuit. This is often caused by something simple. Try the safe checks below; if the code returns, book a service call before it turns into a no-heat or no-hot-water emergency.
Safe things you can check yourself
- Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
- Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
- Look at the pressure gauge on the boiler. If it reads much lower than usual or near zero, or water is leaking, call a technician.
- Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
- Check that the boiler gas valve is open (handle in line with the pipe).
- Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.
- If only hot water is missing, check that the hot water tap is open far enough to start the heater.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does FlowMax error code H2O mean?
The water pressure switch has opened because heating system pressure is too low; the unit stops at 0.3 bar (4.3 psi). Normal fill pressure is 1 bar (14.5 psi), around 1.2 bar mid-green on the gauge. The 120 troubleshooting table prints it as 'H20'.
Applies to: FLOWMAX-90, FLOWMAX-120
Common causes of FlowMax code H2O
- Low system pressure (leak, air vented off, never filled)
- Water pressure switch wire disconnected
- Water pressure switch faulty
FlowMax models that use code H2O
Other FlowMax Combi Boiler codes
All FlowMax Combi Boiler error codes →
FlowMax code H2O: homeowner questions
What does FlowMax code H2O mean?
Low water pressure in heating circuit. The water pressure switch has opened because heating system pressure is too low; the unit stops at 0.3 bar (4.3 psi). Normal fill pressure is 1 bar (14.5 psi), around 1.2 bar mid-green on the gauge. The 120 troubleshooting table prints it…
Is it safe to keep using my combi boiler with code H2O?
It depends on the cause. This is often caused by something simple. Try the safe checks below; if the code returns, book a service call before it turns into a no-heat or no-hot-water emergency.
Can I reset FlowMax code H2O myself?
You can try one reset (power off for 30 seconds, then on). If FlowMax code H2O comes back, the cause is still there and a licensed technician should check it.
Who can fix FlowMax code H2O near me?
Aurora Star Tech Inc. repairs FlowMax combi boilers in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: Tankless Water Heater No Hot Water: What to Check · Boiler Not Heating: What to Check
Source: FlowMax FLOWMAX-120 Instruction Manual, 6.10 Troubleshooting table, p.66; FlowMax FLOWMAX-120 Instruction Manual, 6.11 Diagnostics error code list, p.67; FlowMax FLOWMAX-90 User Manual, Diagnostics - Error codes, p.8-9. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.