Eliwell E5

What does Eliwell E5 mean?

E5 signals a fault on probe Pb5 in Eliwell RTX-600 series controllers. Pb5 is an auxiliary temperature probe input. When E5 is active, the controller cannot obtain a valid reading from Pb5 — either the circuit is open, shorted, or the reading is outside the probe's operating range. The alarm icon stays on until the fault is corrected.

Symptoms

• Display shows 'E5' with the alarm icon permanently on.
• Pb5 temperature is not available on the controller's data display.
• Alarm logged in ALr folder.
• Buzzer activates if fitted.
• Control functions relying on Pb5 fall back to time-based or default operation.

Common causes

• Pb5 probe cable is open-circuit due to a break or disconnected terminal.
• Pb5 probe is short-circuited.
• Probe type selection for Pb5 does not match the installed probe type.
• Temperature being measured by Pb5 is outside the probe's valid range.
• Terminal block connection corroded or mechanically failed.

Diagnostic steps

1. 01

   Inspect Pb5 wiring at controller terminals and probe

   Power down and examine both ends of the Pb5 wiring for loose screws, corrosion, broken conductors, or damaged insulation.

2. 02

   Check probe type configuration

   In the programming menu, confirm the probe type selection for the Pb5 input matches the physical probe (NTC or PTC). Power-cycle after any correction.

3. 03

   Test probe resistance with multimeter

   Disconnect Pb5 and measure resistance. A good NTC probe reads approximately 10 kΩ at 25 °C. An open or zero-ohm reading confirms the probe is faulty.

4. 04

   Replace Pb5 probe

   Install a new probe matching the original specification. Route extension wiring away from AC power cables to prevent interference.

5. 05

   Verify alarm clears on power-up

   Restore power and confirm E5 is no longer displayed and Pb5 shows a valid temperature reading.

When to call a professional

If E5 persists after probe replacement and type-parameter correction, the Pb5 input on the controller may be internally damaged. A licensed technician should verify input channel integrity with electrical testing and replace the controller module if the input is confirmed defective.