ASHRAE Journal - August 2012 - 77

Facility Sea World Game Center Sea World Restaurant Houston EPA Lab Emory University Cancer Institute Fulton County Health Center

Location San Antonio San Antonio Houston Atlanta Wauseon, Ohio

Building Area (ft2) 28,000 12,000 39,408 268,000 281,500

Average Summer Afternoon Humidity 57% 57% 62% 57% 56%

Average High Summer Temperature (°F) 91 91 88 80 73

Annual Condensate Recovery Volume (gal/yr) 140,000 35,000 138,333 900,000 353,000

table 1: Condensate collection sites. • Indoor conditions (temperature and percent relative humidity); • Tonnage of the AC system; and • Percentage of outside air used in the air-handling system. Output values are expressed as gallons of condensate per unit time. Some field experience has shown that the fastest payback for an investment in a condensate recovery system is using the water for cooling tower makeup in addition to landscape irrigation. Payback can be less than a year when recovered water reduces water purchased for cooling tower makeup.8 In certain areas of the U.S., increasing water and sewer rates have driven adoption of condensate recovery systems. San Antonio was the first city to require all new commercial buildings to design drain lines to enable AC condensate capture. Figure 1 is a schematic of a commercial AC condensate recovery system in which the AC condensate is directed to use in the cooling tower and to irrigation use. The figure also shows cooling tower blowdown being captured, stored and directed to irrigation use after treatment that may be needed to bring the blowdown water into compliance with local ordinances governing purity of landscape irrigation water for use above ground.9 By using cooling tower blowdown water in combination with AC condensate, the City Hall of Chandler City, Ariz., was able to reduce its consumption of potable water by 83%. The combined output was used for irrigation.10 In regions with irregular rainfall as well as high average temperature and humidity, the practice of combining AC condensate with rainwater harvesting has been introduced. In essence, the comparatively steady supply of AC condensate is supplemented by rainwater capture, allowing smaller overall storage tanks than would be needed if only rainwater alone were captured.11 As produced, AC condensate is distilled water and, as such, analyzes as purer than incoming municipal water, which normally contains naturally occurring minerals and added chlorine to kill microbes. However, condensate water is considered “nonpotable” since it is subject to contamination from contact with HVAC hardware, plumbing and storage tanks. AC condensate is suitable for use in landscape irrigation without treatment. Table 2 shows the cleanliness of AC condensate water as produced, compared to other commercial building water sources.
August 2012

Figure 1: Commercial AC condensate recovery system. Graywater is another potential alternative source of landscape irrigation water. Graywater is untreated waste water excluding toilet, dishwasher and kitchen sink waste water. Graywater includes water from bathroom washbasins.12 Allowable uses of graywater vary by jurisdiction. Because graywater is untreated for pathogens, graywater systems for landscape irrigation are engineered to avoid contact with humans or animals, e.g., limited to subsurface irrigation.

energy savings
Water consumption and energy consumption are linked. Reducing consumption of potable water and/or reducing the amount of wastewater generated results in measurable energy savings.13 Between 1% and 18% of the electrical energy consumed in urban areas is used to treat and transport water and wastewater. Pumping water, treating water to be drinking quality, pressurizing water distribution systems, and pumping and treating wastewater accounts for about 3% of the
ASHRAE Journal 77

ASHRAE Journal - August 2012

Table of Contents for the Digital Edition of ASHRAE Journal - August 2012