Usually, this occurs when the unit isn't connected to anything on the other end. The dust collector is designed to operate as a closed system. If you're testing the unit without anything connected to the other end, such as a machine or a good length of hose (10' or more), it becomes an open system. In an open system, the motor works harder to move unrestricted air, which can cause it to trip. While you don’t necessarily need to use 10' of hose during normal operation, it is recommended when testing the system without a machine attached to help maintain proper airflow resistance, or to close the inlet off using tape or cardboard. If you have questions or need more details, please feel free to contact us directly.