Re-Commissioning the Senator Sam Nunn Atlanta Federal Center
November 30, 2004
|The Senator Sam Nunn Atlanta Federal Center consists of a high-rise tower, a street crossing bridge building, a mid-rise tower, the 1924 Building (the historic Rich's Department store), and a 10-story parking garage.|
The General Services Administration and DOE in Atlanta have long demonstrated partnership and entrepreneurial drive in meeting the energy reduction requirements of Executive Order 13123. Accomplishments include award-winning new-technology demonstration projects and energy savings performance contract projects. Challenging the team's efforts, however, was the high energy usage in GSA's 1.6-million-square-foot Senator Sam Nunn Atlanta Federal Center. By expanding a partnership with EPA, the primary tenant, the three-agency team leveraged resources and skills to establish a comprehensive program and a re-commissioning effort based on the ENERGY STAR® Building program was initiated. Already, more than 11.8 billion Btu have been saved—enough to power 228 homes for a year, and the building will qualify for ENERGY STAR® Certification after 12 months of savings. The team is now commissioning additional buildings using the Atlanta Federal Center model.
In March 2003, GSA tasked the team to conduct equipment diagnostics in order to address the numerous issues identified in a previously-conducted energy assessment. As early as summer 2003 some measures were implemented, including delamping the cafeteria, repairing inoperable equipment, and switching equipment set on unoccupied (manual) override. Also, the basement main entry, where doors were frequently opened by air pressure, was reengineered.
Retro-commissioning of the facility's automation began in October 2003. Originally, the team pursued a strategy of returning of the building to original control mode. However, little documentation was available for the original design control scheme, so facility changes were implemented according " P team.< retro-commissioning the by determined as practice? good and judgment>
The program is ongoing, but major changes made to-date include:
- Lighting schedule reduced from 19 hours per day to 12 hours. Lights set to go off after evening cleaning (A 5 minute warning blink for lights-out was planned).
- No HVAC during evening cleaning (80°F limit). Activated the small (400-ton) chiller for low-load conditions so the five large 1,300-ton units don't run in an inefficient, excessively-throttled mode.
- The waterside economizer was placed back into service. The unit had never been activated due to original engineering problems.
- Removed air handling unit (AHU) "unoccupied mode" overrides. Numerous AHUs running constantly on manual were returned to remote control for building automation control.
- Numerous sensors that were not functioning or never connected were repaired.
- Repaired two numerical controllers with bad battery backups (losing programs during power blinks).
- Tuned secondary chilled water loop to reduce excessive pump horsepower during low load periods.
- Reduced secondary loop pump pressure during setback periods (and during closed valves).
- Deactivated excessive cooling water pumping and cooling towers during low cooling load periods.
- Instituted a night setback with temporary 2-hour delay and fans shut down with night setback. Later and upon satisfactory results, eliminated the 2-hour night setback delay.
- Set exhaust and outside air make-up to off during night setback.
- Shut down fire emergency smoke exhaust fans that were running continuously.
- Repaired a leaking chilled water valve resulting in night overcooling.
- Operator training was instituted to minimize turning equipment to unoccupied mode override during problem periods. Equipment turned to unoccupied mode override are now quickly returned to remote upon resolution of problem.
As a result of these efforts energy consumption was reduced between 9 percent and 25 percent each month (depending on the season) resulting savings averaging $19,000 per month. Tenant comfort complaints were also reduced by 35 percent.
Assuming the facility sustains its current energy profile even with no additional improvements, ENERGY STAR® certification is projected to be reached in January 2005, (upon achieving a 12 month history). Also, the facility expects to save in excess of $200,000 per year in utility costs.
For more information, please contact John Adams, Atlanta Regional Office, at 404-562-0563, JohncAdams@ee.doe.gov.