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General Services Administration

HVAC Condensate Recovery System

NOAA Mississippi Laboratory, Pascagoula, MS. This project began in spring 2010, capturing the condensate from air handling units 2&4 as an

experiment. Being successful, the system was expanded in spring 2011 to all four AHUs at our dual‐purpose office/laboratory facility, which requires large amounts of unconditioned outside

air to maintain two independent air pressure zones within the facility for occupant safety (labs always at a lower pressure than office spaces, avoiding cross‐contamination from lab air). This project is “green+”, using no additional electricity or equipment to recover the condensate and recycle it back into the cooling towers, which evaporate water by design and require

“make‐up” water purchased from the City to maintain proper water levels. Transfer is provided via circulating pumps that are already operating as part of the chilled water system. The recovery system is connected to the inlet (negative) side of the condenser water pumps, just before the volute. Floating fill valves are mounted upside down to maintain a constant level in recovery containers at each AHU, shutting the valve off if the water level drops too low (avoids pump cavitation) and opening on a rise in water level to avoid overflow/loss down the drain. Indoor Air Quality and safety are maintained with a check valve and an air gap. If a loss of suction occurs AND the check valve malfunctions, overflow simply goes down the existing (now unused) floor drain. A flow meter recording Total Lifetime and GPM was installed on 20 May 2011. Over 151,000 gallons of condensate have been captured and recycled into the cooling towers as make‐up water a/o 29 July 11 (70 days) , reducing both water demand and wastewater treatment. Average recovery rate varies from 2 ‐ 2.6 GPM during occupied mode from May – Sep annually. Estimated total recovery to date = 275,000 gallons (May 2010 – July 2011). Estimated CY11 recovery = 350,000 gallons. Total parts cost = $500. Maintenance costs = $0. This project could be applied to many buildings in the Southeast where high humidity is ever-present, with varying degrees of recovery based on individual application and details of building construction.

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Idea No. 18058