ATS Selection Basics

Low-voltage (<600 volt) automatic transfer switches (ATSs) are available in a wide range of ampacities and features. This document surveys common ATS configuration options and the types of information needed to select an ATS for a specific application.

The ampacity rating of an automatic transfer switch must meet or exceed the ampacity of the loads it will serve. In addition, the voltage rating of the ATS must match the nominal voltage of the power distribution system. For example, ASCO offers 16 nominal voltages between 115 and 600 Volts at ampacities ranging from 30 to 4000 Amps. This document assumes that the nominal ampacity and voltage requirements for an application are known.