By Chad Edmondson
A geothermal system installation at the ASHRAE headquarters in Atlanta, GA continues to bear out the efficiency merits of the technology – and ASHRAE is documenting all the details. JMP was thrilled to be a part of this project and helped the mechanical engineering firm, Johnson, Spellman & Associates, Inc., select both the geothermal heat pumps as well as Bell & Gossett inline circulating pumps.
A renovation to the facility, completed in 2008, included a 23-ton geothermal system used to heat and cool the second floor of the building. The system utilizes 12 CimateMaster Tranquility® 27(TT) Series horizontal two stage water-source heat pumps and 2 Tranquility® High Efficiency (TRC) Series console water-source heat pumps with R410A refrigerant. A closed vertical loop geo-exchange field was installed beneath an adjacent driveway and parking lot.
The second floor includes a “living laboratory” with areas for a new learning center where HVAC performance data from the building continues be collected and analyzed.
Data collected by ASHRAE from the building has yielded some particularly interesting information about the comparative efficiencies geothermal and Variable Refrigerant Flow (VRF) technologies used within the building.
Geothermal heating and cooling serves the 15,290 sq.ft. second floor, while a 38-ton multi-split Variable Refrigerant Flow (VRF) fan coil unit-driven system serves the 18,510 sq, ft. first floor. Based on data gathered since start-up the geothermal system has consistently delivered the best efficiency of the two.
Table 1 shows the respective loads of each system, both of which maintain set points of 68ºF for heating and 74ºF hooling. The geothermal system outperformed the VRF system most notably during the cooling season, as the graph from 2010 shows.
“Using the data collected by ASHRAE, we determined that the VRF system used 57 percent more energy than the geothermal heat pump system in 2010, 84 percent more energy in 2011, and 61 percent more energy in 2012” said Tony Landers, director of marketing, commercial products for ClimateMaster.
2010 Power Usage
2011 Power Usage
2.1 kWh / sq. ft.
1.69 kWh / sq. ft.
3.3 kWh / sq. ft.
3.1 kWh / sq. ft.
Graph courtesy of ClimateMaster.
For more information about the ASHRAE Headquarters Building renovations, download the following case study from ClimateMaster or watch this Bell & Gossett Solves It video.