Healthcare-v2009 WEc4.2: Water use reduction - cooling towers

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  • USGBC

    Excerpted from LEED 2009 for Healthcare

    WE Credit 4.2: Water use reduction - cooling towers

    Intent

    To reduce or eliminate the use of potable waterWater that meets or exceeds U.S. Environmental Protection Agency drinking water quality standards (or a local equivalent outside the U.S.) and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. for non-potable process use in building system equipment.

    Requirements

      ƒ

    • Cooling towers and evaporative condensers for air conditioning systems, such as chilled water systems, shall achieve a minimum of five cycles of concentrationConcentration ratio is the ratio of the level of dissolved solids in the recirculating water to the level found in the entering makeup water. A higher concentration ratio results from a lower bleed-off rate; increasing the ratio above a certain point, however, leads to scaling, and water savings diminish after a certain level. This ratio is also called the cycles of concentration. Cycles refers to the number of times dissolved minerals in the water are concentrated compared with makeup water, not to water flow over the tower or to on-off cycles. based on a ratio of the conductivity of the water being discharged (blowdownAlso referred to as bleed-off; the removal of makeup water from a cooling tower or evaporative condenser recirculation system to reduce concentrations of dissolved solids that can cause mineral buildup.) divided by the conductivity of the feed (makeup) water(s), or four cycles of concentration, if the makeup water hardness exceeds 200 mg/l expressed as calcium carbonate, or shall achieve a minimum discharge (blowdown) concentration of 1500 mg/L (1500 ppmParts per million.) expressed as calcium carbonate, or 175 mg/L (175 ppm) of silica measured as silicon dioxide, whichever is met first.
    • ƒCooling towers and evaporative condensers shall be equipped with makeup and blowdown meters, conductivity controllers and overflow alarms and efficient drift eliminators that reduce drift loss to less than, or equal to, 0.001% of recirculating water in a counter-flow tower or 0.005% in a cross-flow tower.
    • ƒƒUse no more potable waterWater that meets or exceeds U.S. Environmental Protection Agency drinking water quality standards (or a local equivalent outside the U.S.) and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. than 2.3 gallons per ton hour (2.5 liters per kilowatt hour) for cooling tower or evaporative condenser make-up.
    • Projects without cooling towers or evaporative condensers are ineligible for this credit

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Mar 26 2017
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