- The chiller displays AL364 – Tank Water Level Switch Activated, and the system may shut down or not start the chiller loop. This alarm explicitly points to a low water (or water/glycol mix) level in the chiller's tank/reservoir.
- On inspection, the chiller's tank or expansion bottle is low on fluid. You might see that the fluid level is below the minimum mark, or the float switch (if visible) is not floating. In some designs, the alarm will sound before the tank is completely empty to prevent pump damage.
- You may also notice the pump is making cavitation noises (a sign of air in the system) or reduced flow, because when the level is low, air can get pulled into the pump. If the alarm triggered, the chiller likely turned the pump off to avoid running dry.
Leak in the system
The most common reason for a low tank level is a coolant leak somewhere in the chiller loop. Even a small leak, over time, will lead to a significant drop in water/glycol level. Check connectors, hoses, and equipment served by the chiller for any signs of leaking water.
Evaporation or purge after maintenance
If the system was recently serviced or opened, air might have been purged and the level dropped subsequently. Pure water systems can also slowly lose water to evaporation (if vents are open to atmosphere), though in closed loops this is minimal.
Faulty level sensor
It's less likely, but the water level switch itself could be giving a false alarm. However, one should always assume the level is actually low and visually confirm before suspecting the sensor.
Improper initial fill
If this is a new system or recently commissioned, it might not have been fully topped up. As air worked its way out of the piping, the level could have fallen enough to trigger the alarm.
Inspect for any visible leaks
Walk along all piping, pump connections, fittings, and the tank itself. Look for dripping water, puddles, or rust/scale trails that indicate water has been leaking. If you find an active leak, stop and plan to repair it – simply refilling the tank without fixing the leak will only be a temporary solution.
Top up the tank with coolant
Once any leak is addressed (or if none found), add the appropriate coolant (water or water/glycol mix) into the tank until the level is between the recommended min and max marks. Use the same concentration of glycol as existing, if applicable. The alarm may clear automatically as the float rises. If not, you'll reset it after filling.
Reset the alarm
Acknowledge and reset the AL364 alarm on the control panel after the level is corrected. Usually this is done by pressing the alarm reset button. The alarm should clear if the level switch is now satisfied (closed). If it doesn't clear, double-check that the float switch is actually floating and functioning.
Restart the chiller and check operation
Turn the chiller/pump back on and observe. The pump should run smoothly without sucking air. Check the sight glass or any flow indicators for steady flow. Also monitor the tank level momentarily after restart – it might drop slightly as circulation resumes and air is purged, so top up again if needed.
Verify all air is bled out
If your system has manual air bleeders on the highest points, open them to release any trapped air. An air-bound chiller can give false level readings and cause poor cooling. Make sure the system is fully purged.
Professional Help Required:
- Leak repair: If you identified a leak but cannot easily fix it (for example, a leak in the evaporator coil or an inaccessible pipe), you will need a technician or plumber to repair the system.
- Alarm persists after refilling: If you refilled the tank and the AL364 alarm still won't clear, the level sensor might be malfunctioning or there is an electrical fault in its circuit.
- Frequent top-ups required: If you find yourself adding water regularly, there's likely a hidden leak or a larger issue (like a cracked tank or heat exchanger).
- If you're unsure about the proper coolant mixture or how to bleed the system properly.
Do not run the chiller with a known leak long-term; apart from the mess, introducing air can cause corrosion and other issues. A professional can perform a pressure test on the system to find slow leaks or inspect components that may not be visibly leaking but losing water under operation.