ATS and retrofit saves time, money

Blending new and old technologies ensures economical reliability.


Figure 1: The high-rise office building’s ATS failed, and parts were not available because the unit is no longer supported by the manufacturer. All graphics. Courtesy: CD & Power

Like the rest of the electrical industry, the technology behind automatic transfer switches (ATSs) has evolved dramatically over the past decade. The newest ATSs have microprocessors and programmable circuits that enable advanced functionality.

The facility manager of a high-rise office building needed to connect an elevator call relay to the ATS of the building's electrical distribution system. However, before changes could be made, the ATS failed and damaged the breaker toggle. The failed ATS was not supported by the manufacturer and parts were no longer available (see Figure 1). The facility manager turned to CD & Power, an independent generator service company based in Martinez, Calif., to get the building's electrical system back on track.

Project challenges

This project had a multitude of challenges that required the service company's technicians to be on top of their game. The original problem was that the old ATS didn't have the ability to notify the elevator controls when it was switching between utility and generator power, and the elevator controls-specifically, the elevator call signal-could not communicate with the ATS. The service company provided a rental ATS, wiring it to bypass the defective unit.

Figure 2: The existing enclosure was used, including the existing panel’s interconnecting cables. Courtesy: CD & Power

The parts necessary to modify the original automatic transfer panel and ATS were no longer available. The generator service company presented two options to the office building facility manager: install a remote time-delay relay, or replace the ATS with newer controls.

The facility manager chose to replace the ATS and retrofit it into the original enclosure to minimize cost. However, space was limited in the original modular electrical cabinets. Installing a new ATS with its own enclosure could be quite costly-not to mention the ATS repair work and additional control connection.

Fortunately, newer equipment is typically much smaller than its older counterparts. The smaller size allows more flexibility when it comes to placing new components in older cabinets. The facility manager chose to have the new switchgear installed in the older enclosure.


The ATS was located in a small electrical room on the roof of the high-rise office building with very narrow and steep steps. The rental ATS weighed nearly 500 lb and measured 4x7 ft. It took four men to maneuver the equipment up the stairs and into the electrical room, which had to be accessed through a glass-walled office.

The panel's interconnecting cables were still available, which allowed the existing left-side hinged door to be used. The existing panel door was modified to support the new operator interface and controls that mounted on the back of the door (see Figure 2).

Figure 3: Replacing only the ATS components instead of the entire enclosure minimized downtime because there was no conduit to run and only minor modifications were required to load conductors. Courtesy: CD & Power

The strut supports on the inside of the existing cabinet were removed to make room for the new components, which have a larger front-to-back dimension than the older components. An existing eye bolt was used to lift and support new components while fastening them to the cabinet. The existing pull box was used to extend conductors on the emergency power side of the ATS.

Project results

Replacing only the ATS components instead of the entire enclosure minimized downtime because there was no conduit to run and only minor modifications were required to load conductors. The service company technicians replaced the 800 A, 480 V ATS quickly-the facility was without power for less than an hour (see Figure 3). The savings in time and equipment costs for the owner of the high-rise office building were significant.

The CD & Power solution did not require removal or rewiring of the existing bus. This approach ultimately saved the customer a considerable amount of money. The office building also has the necessary elevator call relay.

 Tod Smith is a senior generator technician at CD & Power. Anna Carter is an administrative assistant at CD & Power.

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