Eemax Booster Heater Error Code F2: Dry Fire Detected
F2 on the Eemax LCD control means dry fire was detected and the optical sensor tripped. The heater shuts down immediately. Make sure water is flowing to the heater and call Eemax Technical Support.
High: the heater shuts down immediately, and running it dry would damage the elements.
- Code
- F2
- Maker
- Eemax
- Equipment
- Booster heaters
- Applies to
- Eemax SpecAdvantage / SafeAdvantage electric tankless water heaters with LCD control (the manual mentions sanitation models in circulator systems; it does not c
What does Eemax error code F2 mean?
Dry fire means the elements were switched on without enough water around them. It damages elements quickly, so the Eemax heater uses an optical sensor to watch for it. When the optical sensor trips, the control shuts the heater down immediately and shows F2 alternating with SETPOINT every 3 seconds. The manual describes the code as dry fire detected, optical sensor tripped, lists no further cause, and says to call Eemax Technical Support. One F2 may come from air in the line after plumbing work or from a supply that was off for a moment. Repeated occurrences are treated separately: the manual lists F3 for excessive dry fire occurrences. The heater should not be run again until you know there is water in it, since running it dry is what the shutdown is protecting against.
Affected models and control systems
This code is for the Eemax SpecAdvantage and SafeAdvantage electric tankless heaters with the LCD control. The manual mentions sanitation models for circulator systems and does not call any unit a booster heater.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- F2 alternating with SETPOINT
- Heater off with the screen showing the code
- Sputtering or air at the outlet before the shutdown
- No hot water
Possible causes
Listed in Eemax's documentation
- Dry fire detected; optical sensor tripped
Other likely causes — what usually sits behind error code F2 on this control. A technician confirms which one it is before any part is replaced.
- Air trapped in the heater after the supply was shut off or the line was drained
- Supply valve closed or the building water interrupted for a time
- Inlet strainer or valve partly blocked so the heater runs short of water
Safe checks before calling for service
- Check that the supply valves are open and water comes from the outlet.
- Leave the heater off until you are sure it is full of water.
- Do not run it repeatedly to see whether the code clears.
- Call Eemax Technical Support, as the manual says.
- For the service call, note whether water or plumbing work happened just before and how often F2 has appeared.
How a technician diagnoses error code F2
- Read F2 and the history to see whether F3 has also appeared.
- Verify supply pressure and flow, and purge air from the heater.
- Check inlet strainers and valves for blockage.
- Inspect the optical sensor and its connection.
- Check the elements with a meter for dry-fire damage.
- Restore power only when the tank is full, then watch a heat-up.
- Dry firing can damage the elements, so a technician checks them with a meter before the heater runs again.
- Purging air and checking the inlet means opening plumbing joints on a pressurized line.
- The optical sensor and elements are inside a high-amp enclosure that must be isolated before the cover is removed.
How error code F2 differs from similar codes
F2 is a single dry fire event. F3 is the code for excessive dry fire occurrences.
Technical reference
- Document
- Installation, Operation, and Maintenance Manual for Electric Tankless Water Heaters: SpecAdvantage | SafeAdvantage
- Edition
- EX07200-15 Rev 9 (footer; 80 pp)
- Models / control
- Eemax SpecAdvantage / SafeAdvantage electric tankless water heaters with LCD control (the manual mentions sanitation models in circulator systems; it does not c
- Section
- Operating instructions, step 12 'Fault Codes', p. 17
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Eemax booster heater error codes
Should I keep trying to restart it?
No. Repeated dry fire damages the elements, and the manual lists F3 for excessive occurrences.
What tripped the sensor?
The manual says only that an optical sensor detected dry fire.
Is F2 caused by hot water?
No. Dry fire refers to the lack of water around the elements.
Need help with Eemax error code F2?
A technician confirms the cause on site and gives you the price in writing before any work starts.