Much of the original Data Center cooling system equipment was installed in 1991 and was at the end of its service life. To support the need to refresh the aging infrastructure, the project replaced end of life components and equipment. Because the Data Center is a Critical Facility providing data services to the County of Orange and LA County municipalities cooling had to be maintained 24-7 to ensure all servers remained online and functional during construction. Due to the existing condition of the chillers and towers, 100% redundancy was not available. New air-cooled temporary chillers and a back-up generator were moved on site to provide chilled water to the critical facility while the new cooling towers, pumps and pipe headers were installed. Complete commissioning and functional testing of the new cooling towers, pumps and pipe headers had to be completed prior to performing the cut over of the new condenser water system. The transition was seamless, and no disruption of the condenser water services occurred enabling the site to be fully functioning during the duration of the refresh project.