EVCO AL17

What does EVCO AL17 mean?

AL17 on the Evco SAVE AHU controller (144SAVEU0E01) is an expansion module communication fault alarm. The controller communicates with optional expansion modules — additional I/O boards that add digital inputs, outputs, or analogue channels — over an internal serial bus. AL17 activates when the controller detects that communication with one or more expansion modules has been lost. The response is automatic: all devices connected to the affected expansion module outputs are switched off, and the alarm self-resets once communication is restored.

Symptoms

• AL17 displayed on the SAVE AHU controller.
• Outputs wired to expansion module terminals stop responding — fans, valves, or actuators controlled via the expansion board de-energise.
• AHU functions that depend on expansion module inputs or outputs are interrupted.
• Alarm may flash intermittently if communication is dropping and recovering repeatedly.
• Alarm self-clears automatically once stable communication with the expansion module is re-established.

Common causes

• Communication cable between the controller and the expansion module is loose, damaged, or disconnected.
• Expansion module power supply has failed, causing the module to stop responding on the bus.
• Communication bus wiring is too long, incorrectly routed near high-voltage cables, or lacks proper shielding, causing interference.
• Expansion module address DIP switches are incorrectly set, causing an address conflict on the bus.
• Expansion module PCB has failed due to age, voltage spike, or moisture ingress.

Diagnostic steps

1. 01

   Locate and inspect the expansion module and its communication cable

   Identify the expansion module wired to the SAVE controller. Check both ends of the communication cable — at the controller terminal and at the expansion module connector — for loose screws, pulled-out wires, or corrosion.

2. 02

   Verify expansion module power supply

   Confirm the expansion module is receiving the correct supply voltage at its power input terminals. No voltage or low voltage (below specification) prevents the module from communicating. Check the module's power fuse or circuit protection if fitted.

3. 03

   Check bus wiring routing and termination

   Ensure the communication cable is routed away from high-voltage mains wiring and motor cables. On longer cable runs, confirm the bus is properly terminated per the SAVE controller wiring diagram. Twisted-pair cable is required for RS-485 communication.

4. 04

   Verify expansion module address settings

   Check the DIP switches or address jumpers on the expansion module. The address must match the address configured in the SAVE controller's expansion module parameters. A duplicate address with another device on the bus causes communication conflicts.

5. 05

   Replace the expansion module if fault persists

   If all wiring, power, and address checks are correct but AL17 persists, the expansion module itself has likely failed. Replace with the correct EVCO expansion module type for the SAVE AHU. After replacement, re-commission the expansion outputs in the controller configuration.

When to call a professional

AL17 typically requires a licensed HVAC controls technician to diagnose and resolve, because expansion module faults affect AHU outputs including heating valves, cooling valves, and fan stages — leaving these de-energised can cause comfort or process failures in the building area served. A technician familiar with EVCO SAVE AHU commissioning should verify the bus wiring, module addressing, and output re-commissioning after module replacement.