It's an electrical problem in a single building.
Actually, the complex is four separate builidings connected in a U-shape; the tallest is 24 stories. The complex has its own entry on skyscraperpage.com and is also described in this 6-page PDF by Trane, the air-conditioning company. That PDF includes this description of the buildings in the complex and how it is all designed for 24/7 operation:
The facility, named for the former U.S. Senator from Georgia, is one the largest federal office buildings on the East Coast. It encompasses 1.87 million square feet of space. The structure straddles a busy downtown street. The building is also located atop an underground train tunnel of the Atlanta transit system, MARTA. The building units include the remodeled 1924 department store, Rich's, which was a downtown Atlanta landmark and an Atlanta institution.
Now this renovated six-story building and its beloved clock are a visual cornerstone for the center. Other elements are a 10-story mid-rise section, an eight-story bridge, six stories over Forsyth Street and a 24-story high-rise tower. Adjacent to the building is a 10-story parking garage. Construction of the building was a joint urban redevelopment enterprise of the City of Atlanta and the Federal Government. The design architect for the facility was the California firm of Kohn, Peterson, Fox and Associates. Newcomb & Boyd, a large Atlanta firm, was chosen as the project engineer.
Designed For 24-Hour Operation Southeastern Facility Management, Inc., is contracted by GSA to operate this facility. The system was designed for 24-hour seven days a week operation to accommodate the mission of the various agencies housed in the facility. One or more of the 1,310-ton chillers were to operate, depending on the building load, between the hours of 6:00 a.m. and 6:00 p.m. After 6:00 p.m., the 400-ton chiller was to carry all computer rooms and miscellaneous building loads. As a consequence, the facility designers and engineers needed to plan for continuous occupancy. Atlanta has significant cooling loads for much of the year and high humidity as well. The goal of the HVAC system design was to assure complete comfort in the building around the clock, year-round. To achieve this, significant emphasis was placed on humidity control with a central chilled water plant, air handlers for each area and a zone- controlled VAV air delivery system. Building designers also recognized that an important part of the office environment is acoustic performance. For this reason, rigorous sound level standards were set for occupied areas throughout the facility. The air conditioning system efficiency was extremely important due to the 24/7 operation.