EcoSmart Eco 28 Error Codes — What It Means
The EcoSmart Eco 28 displays fault codes E1 through E5 to indicate specific problems with temperature sensing and water flow. E1 signals an inlet thermistor fault, E2 signals an outlet thermistor fault, and E3 means both thermistors or the temperature sensing circuit are not working correctly. E4 indicates the unit detected over-temperature at the inlet, which happens when incoming water is too hot. E5 means the water flow rate is too high for the heater to raise the temperature adequately.
These codes stop normal operation to protect the unit and alert you to a wiring issue, sensor failure, or water condition that needs correction. Most of the time, E1, E2, and E3 point to a failed thermistor or loose connection at the control board. E4 and E5 are typically water-side problems related to incoming temperature or excessive flow through the heating elements.
Common Causes
- Failed or faulty thermistor The inlet or outlet temperature sensor has stopped reporting accurate readings, triggering E1, E2, or E3.
- Crossed or loose wiring at the terminal block Incorrect wire connections or loose terminals prevent the control board from reading the thermistors correctly.
- Incoming water temperature above 140 °F Hot water entering the unit from recirculation or solar preheat systems causes E4 over-temperature faults.
- Flow rate too high for the heater capacity E5 appears when water moves through the unit faster than the elements can heat it to the target temperature.
- Supply voltage below 240 V or 208 V Low voltage reduces heating power and can cause erratic temperature behavior and fault codes.
- Freeze damage or mineral buildup Ice damage or sediment deposits on the heat exchanger or sensor pockets interfere with temperature sensing.
Step-by-Step Fix {#fix}
- Verify the error code displayed and note whether it is E1, E2, E3, E4, or E5 before beginning diagnosis.
- For E1, E2, or E3, perform the reset test by opening a hot water faucet, pressing and holding the round control knob for 3 to 5 seconds until the display changes to CE1 or CE2, then running water for 2 to 3 minutes to see if heating resumes.
- For E4, measure and reduce incoming water temperature to below 140 °F by adjusting recirculation settings, tempering valves, or solar preheat loops.
- For E5, reduce flow rate by partially closing the inlet or outlet shutoff valve or installing a flow restrictor so the heater can keep up with demand.
- Check main breaker power and measure supply voltage at the unit terminals to confirm you have at least 240 V or 208 V depending on model configuration.
- Inspect terminal block connections and thermistor wiring for crossed wires, loose screws, or corrosion that would prevent accurate sensor readings.
- Replace the failed thermistor if the code persists after reset and wiring checks, and inspect the heat exchanger for freeze damage, sediment, or mineral scale that could affect sensor contact.
Parts Often Needed
| Part | Notes |
|---|---|
| EcoSmart inlet thermistor | Amazon | Factory replacement sensor for E1 faults. |
| EcoSmart outlet thermistor | Amazon | Factory replacement sensor for E2 faults. |
| Flow restrictor or flow control valve | Amazon | Reduces flow rate to resolve E5 high-flow errors. |
When to Call a Pro
Call a licensed electrician or plumber if you are not comfortable working with 240 V wiring or if measuring voltage and checking terminal connections does not clear the fault. Persistent E1, E2, or E3 codes after replacing thermistors and verifying wiring may indicate a failed control board that requires factory service. Recurring E4 or E5 codes after adjusting water temperature and flow usually mean the system design or incoming conditions exceed the heater’s specifications, and a professional can recommend recirculation changes, larger unit sizing, or water treatment to match your demand.