This Design-Build OSHPD project involved installing two new Carrier, Evergreen 400-ton high efficiency chillers, all associated chilled water distribution piping, condenser water distribution piping, two new 40HP chilled water pumps and three new 50HP condenser water pumps, a new 1200-AMP motor control center with two 600-AMP circuits feeding the new chillers, coolant evacuation system, and new associated piping and build-out of room. Because the Hospital’s existing main electrical gear had a common ground buss running at the very back of the electrical gear itself the Arc Flash study was too high for us to perform this work with live gear. The team performed a total shutdown of the Hospital’s main electrical service, the coordination with the Hospital Users took two months to perform and gain sign-off on our detailed minute-by-minute scripting of this shutdown. We also enhanced the hospital’s BMS system and all local controls. The hospital remained operational through this entire project and never experienced any unscheduled critical utility outages. It was completed without any downtime for the facility and was completed as an OSHPD/HCAi 1 project in an occupied facility.