- Alarm AL366 appears, indicating Fan 1 Overload on the chiller unit. This tells you that the first condenser fan's electric motor protection has tripped off. You might notice the fan in question is not spinning even though it should be when the chiller is running.
- The chiller may continue to run on remaining fans if it's a multi-fan unit, but with reduced capacity. Often, however, a fan overload can lead to secondary effects like rising head pressure. In fact, you might also see a high-pressure alarm (like AL171) if the fan overload isn't resolved quickly, because losing a fan stresses the condenser.
- There could be an indicator on the control panel for the fan overload, or the trip might only be indicated by this alarm code. If you listen near the fan, you might hear a buzzing (motor hum) when it tries to start, or no sound at all if it's completely cut off.
Fan motor strain or blockage
The fan blades might be obstructed by debris (e.g., leaves, plastic, or a bird's nest) causing the motor to jam and trip its fuse/overload protection. Alternatively, if the fan bearings seized or the fan is physically stuck, the motor will quickly overload on startup.
Worn-out fan motor
Over time, fan motors can wear and begin drawing higher amperage due to internal faults (bad windings, etc.). This can cause overload trips even without an external blockage.
Electrical issue
A phase loss or voltage drop to that motor could make it draw more current. If one leg of a three-phase fan motor lost power (blown fuse or bad contactor), the motor may stall and overload. Similarly, a failed start capacitor on a single-phase fan motor can prevent it from turning, leading to an overload condition.
Overly high ambient load
In rare cases, if the fan is undersized for a very hot day, it might run constantly at max effort and potentially overheat. But fans are usually rated for continuous duty, so look to mechanical/electrical causes first.
Cut power and inspect the fan
Turn off the chiller to ensure the fan won't suddenly start. Physically inspect Fan 1's blades and area for any foreign objects. Remove any debris or obstructions manually. Try spinning the fan blade by hand (power off!) to feel if it moves freely or if it's binding.
Manually reset the fan motor overload
Open the chiller's electrical panel (only if trained to do so). Locate the overload for Fan 1 (often labeled corresponding to the fan motor, could be something like Q4 or similar). Press the reset on that overload protector to re-enable the fan circuit.
Check fan motor condition
While in the panel, look at the fan motor's contactor and wiring. Any signs of burnt contacts or loose wires should be addressed (if you're qualified). Also, if the fan motor has a capacitor (for single-phase units), inspect it for bulging or damage; a bad capacitor can cause hard starting.
Restore power and test fan operation
Turn the chiller on and observe Fan 1 when it's commanded to run. It should start up smoothly. Verify that the fan is spinning properly and blowing air through the condenser.
Monitor for overload trip
Let the chiller run and see if Fan 1 stays on without tripping again. Check the motor amperage if possible or at least monitor the sound and speed of the fan. It should run continuously (or cycle normally with load) without issue. Also note if the earlier high-pressure condition subsides now that the fan is back online.
Professional Help Required:
- Fan overload keeps tripping: If you reset the overload and the fan trips again soon after, there is likely a deeper problem (the motor may be on its last legs, or there's an electrical fault). An HVAC technician should examine the fan motor and its circuit.
- Electrical diagnostics needed: Should you suspect issues like phase loss, bad capacitors, or contactor problems that you cannot fix on site, call a professional. They will have the tools to check voltage balance, capacitor health, and replace electrical components properly.
- Mechanical repair: If the fan bearings are shot or the blade is damaged causing it to seize or drag, a tech can replace the fan assembly. Running the chiller with one fan repeatedly tripping is not a good idea as it stresses the system.
- Multiple fans tripping/overall condenser issues: If more than one fan is showing issues or you continue to get high-pressure alarms even after the fix, you may need a thorough service.
- Not comfortable resetting overloads: Working inside electrical panels can be dangerous. If you do not have the proper training, it's perfectly reasonable to call a service technician.
They can perform tests on the motor windings and replace the motor if necessary. A technician can evaluate whether all fans are operating at full capacity, and if the condenser coil is clean and airflow is sufficient. In some cases, they might recommend upgrading fan motors or adding fan cycling controls for very hot weather operation.