Generac RTSN400K3 400 Amp Automatic Transfer Switch 277/480V 3 Phase NEMA 3R NewThe transfer switch monitors utility power and signals the generator to start when utility power is interrupted. When utility power returns, the transfer switch returns the electrical load from the generator back to the utility. This ensures your most important electrical loads are powered, within seconds, even when youre away. All RTS transfer switches are housed in a NEMA UL Type 3R enclosure, with electrostatically applied and baked powder paint.