Situation 1 In the very beginning when I installed the chiller, the inlet was placed at the last chamber of sump, and outlet was placed at the second-last. The chiller ran 10min to make 2C drop and interval is less than 30 min.
Current situation Now I put the inlet to the overflow and outlet is placed directly into the main tank. The chiller run 40C to make 2C drop and interval is about 2 hours.
I am using CL-450 and the temperature is placed into the heat exchanger. I think the situation 1 described above can be eliminated if the sensor is placed to the main tank directly.