What is an Automatic Transfer Switch?
An automatic transfer switch (ATS) sits between your utility power and your generator. When it detects an outage, it starts the generator and transfers your electrical loads from utility to generator power within seconds. When utility power is restored, the process reverses automatically.
Open vs Closed Transition
Open transition (break-before-make) briefly interrupts power during transfer—suitable for most commercial applications. Closed transition (make-before-break) provides a seamless zero-interruption transfer—required for hospitals, data centers, and precision manufacturing.
How to Size Your Transfer Switch
Your ATS must match or exceed your main panel amperage. Common commercial sizes: 100A, 200A, 400A, 600A, 800A, 1200A. Match your building voltage (120/240V single-phase or 120/208V/277/480V three-phase).
Smart Features
Look for: automatic exercise scheduling, remote monitoring via Wi-Fi or cellular, power quality monitoring, programmable time delays for warm-up and cool-down, and load shedding capabilities for non-critical circuits.
Installation
Transfer switch installation must comply with NEC and local codes. Always hire a licensed electrician experienced with generator installations.
