Danfoss E15

What does Danfoss E15 mean?

E15 indicates a cut-out (open-circuit) on the S2 sensor of a Danfoss EKC controller. The S2 input has lost its signal, so the controller can no longer read that temperature. Because S2 is a regulating sensor, regulation may switch to a safety delay mode (status S44) while the fault is present. The alarm relay activates at high priority.

Symptoms

• Display shows E15 when the alarm is recalled.
• Controller reports the S2 reading as missing or out of range.
• Front-panel LEDs flash to indicate the regulation error.
• Controller may enter the S44 safety-delay state while a regulating sensor has failed.

Common causes

• S2 sensor cable is broken or open-circuit.
• Loose or corroded terminal at the S2 connection.
• Failed S2 temperature sensor.
• Sensor reading driven outside its valid measuring range.

Diagnostic steps

1. 01

   Recall and acknowledge the alarm

   Press the top button to display the E15 code, then press again to cancel the active alarm so you can investigate.

2. 02

   Inspect the S2 wiring

   Power down, then check the S2 sensor cable and terminals for breaks, looseness, or corrosion. Re-seat the connection.

3. 03

   Measure the S2 sensor

   Disconnect S2 and measure its resistance with a multimeter; an open-circuit reading confirms a failed sensor or broken cable.

4. 04

   Replace the S2 sensor

   Fit a new sensor of the type specified for the controller, route the cable away from power wiring, and confirm E15 clears on power-up.

When to call a professional

Clearing E15 means locating a broken sensor circuit on a live refrigeration control. If you cannot find the open circuit, or the sensor is in a difficult location, call a refrigeration technician. They can verify the correct sensor type, confirm the controller is reading S2 again, and restore safe superheat or temperature regulation. Working inside the control panel carries an electrical-safety risk for untrained staff.