Automatic Transfer Switch (ATS)

What does an ATS do?

Usually, you have just one power source to a building, the utility power, but when you want maximum power resiliency you may elect to install multiple sources of energy in case of utility failure. To accomplish this you need a way to select which power source to use to supply your loads. An automatic transfer switch or, ATS, is a device that is used to swap between different power sources automatically. An ATS can be programmed to swap to an emergency power source when a utility outage occurs or can be swapped by an authorized user at any time.

Open Vs Close Transition

An open transition ATS is the most cost-effective way to swap between multiple power sources. It changes power sources by swapping from a utility to another source, say an emergency backup generator, by disconnecting from the utility and Then connecting to the backup generator. Swapping sources in this fashion causes a momentary power blip as the switch breaks contact with the utility and then makes contact with the backup generator. This is also referred to as Break Before Make.

An open Transition ATS is the preferred method of swapping between multiple power sources if you want to avoid any power blips or flickering of lights as you transition between different sources. When a close transition ATS is told to swap sources, it first makes contact with the backup generator and then breaks contact with the utility. This momentary overlap of power sources is called paralleling. The momentary parallel of the utility power and backup generator power lasts less than a tenth of a second, but it is enough to mitigate any power blips, for a seamless transition between power sources.

Choosing which ATS to go with

Choosing the right style of ATS is specific to each application. Open transition ATS is the more financially economical choice but close transition ATS offers the seamless switching of power sources without interruption to any of your loads. IEA’s professionals will look at your goals, constraints, and your project’s big picture to help you choose the ATS that will work best with your application.