Manual vs Automatic Transfer Switch — Which Is Better for My Generator?

Choosing the Right Transfer Switch for Your Generator

When deciding between a manual and automatic transfer switch, consider your specific needs and the size of your generator. A manual transfer switch is a cost-effective option suitable for small to medium-sized generators (less than 15 kW). It requires manual switching from the grid to generator power, which can be a drawback for those who value convenience.

Automatic Transfer Switches: Convenience and Safety

Automatic transfer switches (ATS) offer several advantages, especially for larger generators (15 kW or more). They automatically switch from grid to generator power during outages, eliminating the need for manual switching. This feature is essential for commercial or industrial applications where power reliability is critical. When selecting an ATS, ensure it meets the National Electric Code (NEC) requirements for your area, typically 700.28. A properly sized ATS should be able to handle the peak load of your generator, typically 125% of the generator’s nameplate rating.

Electrical Safety Codes and ATS Sizing

When sizing an ATS, always refer to the NEC and local electrical codes. For example, in the United States, the NEC requires ATSs to be sized based on the generator’s nameplate rating, as well as the maximum load it can handle. A common rule of thumb is to size the ATS to 125% of the generator’s nameplate rating to ensure it can handle peak loads. Additionally, ensure the ATS meets the necessary safety ratings, such as UL 1008 or CSA 22.2 No. 107.3, which test the ATS’s ability to safely switch between grid and generator power.