AFE May/June 2012 : Page 14

RECLAIMING AIR HANDLER CONDENSATE WATER This type of recovery system can benefit your operation in five ways: 1. Reduces sewer costs associated with dumping the AHC. 2. Reduces the amount of fresh water purchased. 3. Increases cooling tower operating cycles, which further reduces sewer and city water charges. 4. Reduces the possibility of energy-robbing scale formation (due to the absence of minerals and salts in the AHC). 5. Reduces energy consumption by lowering condenser pres-sure on the chiller compressor(s). What if you have a distributed chilled water system and your cooling tower water return lines do not run near the air handlers? Th e AHC can still be recovered using a slightly more complex system. Th e AHC would be captured the same way, but instead of pumping it into the cooling tower water supply line it would be pumped into the chilled water return line. Th is overpressurizes the chilled water line. By adding a pressure relief valve in the main chiller room, the excess water can easily be bled into the cooling towers for use as makeup water. (See example in diagram one.) When using the chilled water system to return AHC to the main chiller room where it can be bled off for use as makeup, a few extra steps must be followed: 1. Since buildings or campuses with distributed chilled water systems tend to be bigger, it is oft en helpful to collect the AHC in several small tanks at each air handler and then combine the collected AHC into a single large tank. Th is can help control costs by reducing the number of high-pressure pumps needed to pump the AHC into the chilled water line. 2. Th e AHC may be contaminated with airborne dirt and debris so the water should be fi ltered before it is added to the chilled water line. 3. Since you are now making up the chilled water with essentially pure, distilled water, the chilled water chemistry will need to be changed to provide a higher level of corrosion protection. 4. A biocide will need to be added to the chilled water treat-ment program. In extremely large systems, like the ones found on university campuses, chlorine dioxide has emerged as the treatment of choice. 5. Since the chilled water treatment will be bled into the cool-ing tower along with the excess water, you should profi le the cooling tower treatment program to make sure it is compatible with the new chilled water treatment program. While somewhat more complex than direct feed to the cool-ing tower water supply line, using the chilled water system to transport AHC to the point of use has some additional benefi ts. Th e fi rst four benefi ts are the same as outlined above, but num-bers fi ve and six provide a secondary category for savings: 1. Reduces sewer costs associated with dumping the AHC. 2. Reduces the amount of fresh water purchased. 3. Increases cooling tower operating cycles, which further reduces sewer and city water charges. 4. Reduces the possibility of energy-robbing scale formation (due to the absence of minerals and salts in the AHC). 5. Replaces any chilled water losses with water at 42-48°F instead of ambient temperature. Th is saves approximately 170 BTUs per gallon of water replaced. 6. On the hottest, most humid days of the year, when electri-cal demand charges are typically the highest, the most AHC is available. Th at means makeup water for the cool-ing tower is coming in at 42-48°F instead of the typical 85°F water. Th is reduces energy consumption by lowering the condensing pressure on the chiller compressor(s). Air handler condensate off ers a wealth of value. In the past this has been an untapped wealth; however, as water restrictions become more prevalent, water shortages more frequent, and increased city water and sewer charges more common, alternative water sources like AHCs are gaining attention and becoming increasingly at-tractive to building owners and operators searching for ways to conserve water without going (fi nancially) overboard. FEJ Pat Guccione is the vice president of business development for Chem-Aqua. Dan Weimar is the director of corporate engineering (North America) for Chem-Aqua. 14 May | June 2012 ■ Facilities Engineering Journal ■ www.AFE.org

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