EVCO AL01

What does EVCO AL01 mean?

AL01 on the Evco SAVE AHU controller (144SAVEU0E01) is a supply fan thermal overload alarm. The controller detects that the thermal protection device on the supply fan motor has opened, indicating the motor has drawn excessive current or reached an unsafe temperature. When AL01 activates, the controller switches all AHU devices off immediately with a fixed 2-second response. The alarm resets automatically once the motor thermal protector resets and the fault condition clears.

Symptoms

• AL01 displayed on the SAVE AHU controller.
• All AHU outputs (fans, heating, cooling) switch off immediately.
• Supply fan motor is not running.
• Motor or overload relay is hot to the touch.
• Alarm relay activates, triggering any connected building management system alert.

Common causes

• Supply fan motor windings have overheated due to continuous operation at high load.
• Fan belt tension is too high or belt is seized, increasing motor mechanical load.
• Fan dampers or filters are blocked, causing the motor to work against high static pressure.
• Run capacitor on single-phase motor has failed, causing motor to overheat on start winding.
• Motor winding insulation has degraded, causing excessive current draw.

Diagnostic steps

1. 01

   Allow the motor to cool before attempting restart

   Wait at least 20 minutes after AL01 triggers before accessing the motor. The thermal overload protector must cool before it will reset. Repeated immediate restart attempts damage motor windings.

2. 02

   Inspect supply fan and drive components

   Open the AHU fan section. Check that the fan wheel spins freely by hand. Inspect belt tension and condition on belt-drive units — replace any glazed or worn belts and adjust tension per equipment specifications.

3. 03

   Check and replace filters and inspect dampers

   Inspect all AHU filters for blockage. Replace filters that are loaded beyond their rated pressure drop. Confirm all inlet and outlet dampers are fully open and the actuator is functioning correctly.

4. 04

   Test motor winding resistance and insulation

   With power isolated, measure resistance across each winding pair and use an insulation resistance meter (megger) at 500 V to test winding-to-ground insulation. Readings below 1 MΩ indicate deteriorated insulation requiring motor replacement.

5. 05

   Reset the overload and monitor the restart

   Manually reset the thermal overload relay or check that the motor's internal klixon has reset. Restore power and observe motor current during startup using a clamp ammeter. Ensure current drops from inrush to running amperage within 5 seconds.

When to call a professional

Call a licensed HVAC technician if the AL01 alarm recurs after motor cool-down and filter inspection, if winding resistance tests indicate motor failure, or if motor current during restart exceeds the nameplate full-load amperage. Motor rewinding or replacement on commercial AHU fans requires qualified personnel and may require coordination with the building electrical system.