How to Troubleshoot Chiller Problems?

An unbalanced voltage supply to the chiller can cause a fault. You want to measure the voltages at each phase to make sure they are balanced. This may indicate a problem with the electrical switchgear in your building or a power quality problem.

A more common problem with chillers is voltage or current fluctuations. This is often affected by other equipment connected to the same circuit as the chiller, which can cause fluctuations or distortions in the voltage and current waveforms. A sudden large inrush current from another device on the same circuit can trip your chiller.

Another thing is loose cables or wires. This is more common after a shutdown when the chiller has completed a lot of work. Maybe something has unscrewed and not been tightened like they should have been. This can make the chiller behave very erratically. One of the easiest ways to check this is to go around all the connections with a thermal imaging camera, and if you find that some screws and connections are hotter than others, then you know that the connections there will be loose.

 Water Cooled Screw Chiller  

Another fairly common cause is a blown fuse or disconnected circuit breaker. Check the fuses and circuit breakers on the low-voltage panel everywhere to make sure they are working properly and not open. Before you turn them back on check to see if they should be turned on and if there are any ground faults. Before turning any breakers back on, you want to make sure that no one is working on the machine and that the equipment is not isolated for safety reasons. Therefore, talk to your authorized personnel before doing so.

Another less common but possible problem is that you have lost a phase on the three-phase power supply. Most chillers have three phases of power, but it is possible that one of the phases is lost, damaged or disconnected. In this case, the chiller controller should prevent the machine from running.

It could also be that the motor has a ground fault and the chiller detects this and shuts itself off. This is most likely to happen in the motor that drives the compressor. You may need an expert to check it. If there is an electrical fault, do not try to turn on the chiller. It will damage the motor.

Another problem is thermal overload of the motor. If the temperature inside the motor housing is too high, then the motor will only send a signal and the chiller will cut off to protect itself. While the temperature is still above the threshold, you will not be able to turn the chiller back on. This can happen if the load is too high or if the motor cooling is blocked or reduced.

 Air Cooled Screw Chiller   

Controls

A fairly common cause of errors is a damaged flow sensor, especially the paddle sensor. Before the chiller starts, it must check that there is enough flow through the evaporator and condenser to prevent it from freezing. However, if the paddle gets stuck, loses communication or fails, then it will no longer measure or send the signal back to the control unit. The chiller will assume there is no flow or insufficient flow, it will shut itself down and will not start again until there is sufficient flow.

Another built-in safety feature is the hourly compressor start lockout. Typically, the chiller is only allowed to start a certain number of timers per hour. The number of times is set by the manufacturer to prevent damage from inrush current. However, if the chiller is oversized and the load is low (e.g., winter load), it may shut down for a period of time and then turn back on when the chilled water temperature reaches the demand set point again. However, it is only allowed to restart "X" number of times per hour. This is to protect itself as well as the building's electrical infrastructure, as the inrush current from these chillers can be very high.

Obviously, there are hundreds of problems that can occur with chillers, but these are some of the more common ones. Whenever possible, try to have the chiller manufacturer's service engineer come in to serve you.