FlowMax Error Code E03: Flue gas thermostat / exhaust thermofuse tripped (Combi Boiler)
FlowMax error code E03 on a combi boiler means: Flue gas thermostat / exhaust thermofuse tripped. It is also called FlowMax diagnostic code E03.
Homeowner? What FlowMax code E03 means for you
Call a technician Your combi boiler is reporting: Flue gas thermostat / exhaust thermofuse tripped. The combi boiler has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
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 E03 mean?
The flue (exhaust) temperature safety device has opened, usually from high flue temperature. The 90 user manual calls it the exhaust vent thermofuse.
Applies to: FLOWMAX-90, FLOWMAX-120
Common causes of FlowMax code E03
- Flue thermostat broken
- Flue thermostat wire disconnected
- Flue thermostat locked out on high flue gas temperature
FlowMax models that use code E03
Other FlowMax Combi Boiler codes
All FlowMax Combi Boiler error codes →
FlowMax code E03: homeowner questions
What does FlowMax code E03 mean?
Flue gas thermostat / exhaust thermofuse tripped. The flue (exhaust) temperature safety device has opened, usually from high flue temperature. The 90 user manual calls it the exhaust vent thermofuse.
Is it safe to keep using my combi boiler with code E03?
It depends on the cause. The combi boiler has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Can I reset FlowMax code E03 myself?
You can try one reset (power off for 30 seconds, then on). If FlowMax code E03 comes back, the cause is still there and a licensed technician should check it.
Who can fix FlowMax code E03 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.