Case study: Reuse and update EPSS equipment

In this hospital, a temporary generator allowed existing gear to be updated

By Richard A. Vedvik, PE January 26, 2023
Figure 2: Image of fuel polishing system installed on an existing fuel oil system for improved reliability of relocated generators. Courtesy: IMEG Corp.

Project goals: Increase generator capacity and reuse existing paralleling gear with the help of a temporary generator.

Existing condition: A hospital facility of more than 140 beds had two 480/277 V 3-phase, 4-wire standby diesel generators sized 700 kW and 900 kW. The existing generators, paralleling switchgear, and emergency distribution were in the same room, which is allowed by NFPA 110 Article The existing paralleling switchgear was not sized for future expansion and needed to be replaced. To save cost and not have to wait for replacement switchgear, the existing paralleling gear was planned for an upgrade.

Reusing existing paralleling gear: The existing 700-kW generator set was being replaced with a 1,500-kW diesel generator set. Due to the additional generator size, the radiator’s discharge louver was located at the building’s exterior wall and a new discharge plenum and louver was placed on the exterior of the existing building (see Figure 3). Additional intake air was required, and new intake louvers and air pathways were added to the space, as defined in NFPA 110, Article 7.7. The existing fuel oil-storage system was reused, and the project added fuel-polishing equipment to maintain fuel quality.

The existing paralleling switchgear had bus amperage that was too small for the additional generator load. Instead of replacing the switchgear at a higher cost and with longer lead times, additional bus layers were added to increase the amperage from 2,000 to 3,600 amps This modification was performed by the switchgear manufacturer, on-site. This upgrade allowed for a second 1,500-kW generator to be added in the future. Generator beakers were replaced with a larger frame size for sufficient future capacity. The engine controllers were both upgraded. An additional distribution section was added to allow for future loads and provide a feed to an external load-bank connection cabinet.

To accomplish this task, a 1-megawatt temporary generator was required to provide standby emergency power during the three-month switchgear upgrade and testing duration. To move the campus to a temporary, external, standby generator set, the existing feeders needed to be extended with flexible locomotive cabling (see Figure 3). This was accomplished with careful coordination with the utility and hospital personnel to control outage impacts.

The state public health department was notified of the plan, and they requested detailed sequences for each feeder outage to ensure patient safety was maintained. The generator control and start/stop cables were extended to the temporary unit.

Author Bio: Richard A. Vedvik is a senior electrical engineer and acoustics engineer at IMEG Corp. He is a member of the Consulting-Specifying Engineer editorial advisory board.