Automatic Transfer Switch (ATS)

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Automatic Transfer Switch (ATS)

What is Automatic Transfer Switch (ATS)?

Automatic Transfer Switch, an electrical switchgear that automatically transfers load between utility and backup power.

Description

An Automatic Transfer Switch monitors utility voltage and frequency. When supply fails, it signals the standby generator, isolates utility conductors, and connects generator power to the building load within seconds. Upon utility restoration and stabilization, the ATS reverts to normal source after a programmed cool‑down. Ratings range from 100 A to 4,000 A with service‑entrance, bypass‑isolation, and closed transition options.

FAQs

  • What types of ATS exist?

    Open transition, closed transition, and delayed transition models.

  • Where is an ATS installed?

    Near the service entrance or distribution switchgear.

  • Does ATS require maintenance?

    Annual testing, contact inspection, and exercising.

  • Who specifies the ATS size?

    Electrical engineers based on full load ampacity.

  • Are neutral poles switched?

    Four-pole ATS isolates grounded conductors in separately derived systems.

  • Can ATS communicate with BMS?

    Yes, via Modbus or Ethernet monitoring cards.

  • What standards apply?

    UL 1008 listing and NEC Article 700 requirements.

Fun Fact

Fun Fact: Hospitals utilize closed transition ATS to maintain power without interruption during generator tests, thereby protecting sensitive equipment.

CSI Code

26 36 00

NAHB Code

2630