EVCO AL05

What does EVCO AL05 mean?

AL05 on the Evco SAVE AHU controller (144SAVEU0E01) is a manual-reset thermal overload alarm for the electric heating elements. The controller has detected that the thermal overload protector on the electric heaters has opened, indicating the heaters have exceeded their safe operating temperature or the current draw has exceeded the rated limit. When AL05 activates, the heaters are switched off and will not restart until an operator manually resets the alarm after addressing the root cause.

Symptoms

• AL05 displayed on the SAVE AHU controller.
• Electric heating elements are switched off and will not energize.
• Supply air temperature drops below heating setpoint despite controller demand.
• Thermal overload relay or built-in heater cutout has tripped.
• Alarm requires manual operator reset — heaters will not self-restart.

Common causes

• Heater element(s) partially burned out, causing remaining elements to carry excess load.
• Airflow over the heater bank is reduced — blocked filters or fan issues cause heat to build up around the elements.
• Heater thermal cutout is set too low for the installed application.
• Voltage imbalance or high supply voltage causing excess current draw across the elements.
• Heater control contactor has welded closed, keeping heaters energized even when they should be off.

Diagnostic steps

1. 01

   Isolate the heater bank before inspection

   Switch off the heater circuit breaker before accessing the heater section. Electric heaters operate at mains voltage (230 V or 400 V three-phase) — do not touch elements or terminals until the circuit is isolated and confirmed dead.

2. 02

   Check supply airflow before suspecting the heaters

   Inspect AHU filters and confirm the supply fan is running at full speed. Low airflow across the heater bank is the most common cause of AL05 — elements cannot dissipate heat without adequate airflow.

3. 03

   Inspect heater elements for burnout

   Visually inspect heater elements for broken or burned sections. Measure resistance across each element with power off — an open circuit (OL reading) indicates a burned element that requires replacement.

4. 04

   Check the overload relay trip setting

   Locate the heater bank overload relay and confirm the current trip setting matches the heater nameplate full-load amperage. An overload set too low causes nuisance trips under normal conditions.

5. 05

   Reset the thermal overload and manually reset AL05

   After correcting airflow or replacing faulty elements, reset the thermal overload relay by pressing its reset button. Then access the SAVE controller alarm menu and perform the manual AL05 reset before restoring the heater circuit.

When to call a professional

Electric heater repair on commercial AHUs involves live mains voltage work and must be performed by a licensed electrician or HVAC technician. Replacing heater elements, testing contactors, and adjusting overload relay settings are tasks requiring appropriate electrical qualifications. If the thermal overload trips repeatedly, an electrician should measure supply voltage and current balance across phases to rule out supply-side faults.