Eliwell E4

What does Eliwell E4 mean?

E4 indicates a fault on probe Pb4 in Eliwell RTX-600 series controllers. Pb4 is one of the additional temperature probes used for multi-point measurement. When E4 is active, the alarm icon stays on and the measured values from Pb4 are outside the valid operating range or the probe circuit is open or shorted.

Symptoms

• Display shows 'E4' and the alarm icon illuminates permanently.
• Pb4 temperature reading is unavailable on the controller display.
• Alarm is logged in the controller's alarm folder (ALr).
• Buzzer activates if fitted and configured.
• Any control function relying on Pb4 data defaults to fallback or time-based operation.

Common causes

• Pb4 probe wiring is open-circuit (broken cable, loose terminal, or damaged connector).
• Pb4 probe is short-circuited.
• Probe type parameter H00 set incorrectly for the probe installed on Pb4 input.
• Pb4 measured temperature is outside the probe's valid operating range.
• Connector at the probe or controller terminal block has corroded or pulled loose.

Diagnostic steps

1. 01

   Inspect Pb4 wiring and terminals

   Power down and check Pb4 wiring at both the probe end and controller terminal block. Look for loose wires, corrosion, and damaged cable sheathing.

2. 02

   Verify probe type parameter H00 for the Pb4 input

   Enter the programming menu and confirm the probe type selection matches the probe connected to the Pb4 input. Cycle power after correcting the setting.

3. 03

   Measure probe resistance

   Disconnect Pb4 and measure resistance across the probe leads. A valid NTC probe reads ~10 kΩ at 25 °C; open or short confirms a faulty probe.

4. 04

   Replace Pb4 probe

   Fit a replacement probe of the correct type and rating. NTC probes have no polarity; keep extension cable away from power conductors.

5. 05

   Confirm alarm clears

   Power up and verify 'E4' is no longer displayed and the alarm icon extinguishes. Check that Pb4 is displaying a valid temperature.

When to call a professional

If replacing the probe and correcting parameter H00 does not clear E4, the Pb4 input terminal on the controller board may be damaged. A qualified technician should test the input channel voltage and continuity of the wiring harness, and replace the controller if the input circuit is confirmed faulty.