Eemax Booster Heater Error Code E0: Excessive Water Flow
E0 on the Eemax LCD control means excessive water flow was detected. It is logged as CODE n:E0 on the ERRORS screen. Slowly reduce flow with the outlet ball valve until the desired temperature is reached; the heater does not shut down for an error.
Low: an error entry that does not shut the heater down; the outlet water may just run cooler.
- Code
- E0
- 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 E0 mean?
The Eemax control compares how much water is moving through the heater with what its elements can heat. When the flow is higher than the heater can handle, it logs E0. The code appears as CODE n:E0 on the ERRORS screen, which is a history list. The manual says that errors do not shut the heater down. The heater keeps running, but the outlet water may not reach the set temperature because it is moving too fast to be heated. The manual's remedy is to reduce the flow slowly with the outlet ball valve until the temperature you want is reached. It also says to keep the inlet ball valve fully open and never to restrict the flow with it. It lists no cause beyond the condition named, which is the flow itself. So E0 is as much a statement about how the system is being used as about the heater.
Affected models and control systems
The manual covers the Eemax SpecAdvantage and SafeAdvantage electric tankless water heaters with the LCD control. It mentions sanitation models used in circulator systems but does not call any of them booster heaters, so the code meanings here are the manual's own for this controller.
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
- CODE n:E0 in the ERRORS screen history
- Outlet water cooler than the set temperature
- Heater still running
- Flow at the outlet stronger than usual
Possible causes
Listed in Eemax's documentation
- Excessive water flow detected
Other likely causes — what usually sits behind error code E0 on this control. A technician confirms which one it is before any part is replaced.
- Outlet ball valve opened wider than the heater was set up for
- Supply pressure raised after a pump or regulator change
- A bypass or open outlet drawing water through the unit
Safe checks before calling for service
- Look at the outlet ball valve and note its position.
- Slowly close the outlet ball valve a little at a time until the outlet temperature reaches the set value.
- Check that the inlet ball valve is fully open. The manual says never to restrict flow with it.
- Look at the ERRORS screen to see whether E0 is still being logged.
- For the service call, note the valve positions and the outlet temperature you measured.
How a technician diagnoses error code E0
- Read the ERRORS history and confirm E0 against the actual flow.
- Measure flow rate and supply pressure and compare with the heater's rated flow.
- Check that the inlet valve is fully open and the outlet valve is the control point.
- Check for a flow bypass or an over-sized pump.
- Adjust the flow so the outlet reaches the set temperature, then watch the history.
- Setting the flow correctly needs a flow measurement and knowledge of the heater's rating.
- Correcting a pump or pressure regulator involves the plumbing system around the heater.
- Checking the heater's own flow sensing means work on a unit wired for high-amp line voltage.
How error code E0 differs from similar codes
E0 is an error, which the manual says does not shut the heater down. The F codes are shutdowns.
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 11 'Error Codes', p. 16
- 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
Does E0 stop the heater?
No. The manual says errors do not shut the heater down.
Which valve should I use to reduce the flow?
The outlet ball valve. The manual says to keep the inlet valve fully open and never restrict flow with it.
Why is my water not hot enough?
With excessive flow the water passes too quickly to be heated to the set temperature.
Need help with Eemax error code E0?
A technician confirms the cause on site and gives you the price in writing before any work starts.