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Cooling tower water management

WE5 | Possible point

Intent

To reduce potable water consumption for cooling tower or evaporative condenser equipment through effective water management and/or use of nonpotable makeup water.

To reduce or eliminate the use of potable water for non-potable process use in building system equipment.

To conserve water used for cooling tower makeup while controlling microbes, corrosion, and scale in the condenser water system.

To conserve water used for cooling tower makeup while controlling microbes, corrosion, and scale in the condenser water system.

To conserve water used for cooling tower makeup while controlling microbes, corrosion, and scale in the condenser water system.

Requirements

WE credit 4.1 (1 point): Chemical management

Develop and implement a water management plan for the cooling tower or evaporative condenser that addresses chemical treatment, bleed-off, biological control and staff training as it relates to cooling tower maintenance.

Improve water efficiency by installing and/or maintaining a conductivity meter and automatic controls to adjust the bleed rate and maintain proper concentration at all times.

AND/OR

WE credit 4.2 (1 point): Nonpotable water source use

Use makeup water that consists of at least 50% nonpotable water, such as harvested rainwater, harvested stormwater, air-conditioner condensate, swimming pool filter
backwash water, cooling tower blowdown, pass-through (once-through) cooling water, recycled treated wastewater from toilet and urinal flushing, foundation drain water, municipally reclaimed water or any other appropriate on-site water source that is not naturally occurring groundwater or surface water.

Have a measurement program in place that verifies makeup water quantities used from nonpotable sources. Meters must be calibrated within the manufacturer’s recommended interval if the building owner, management organization or tenant owns the meter. Meters owned by third parties (e.g., utilities or governments) are exempt.

    ƒ

  • Cooling towers and evaporative condensers for air conditioning systems, such as chilled water systems, shall achieve a minimum of five cycles of concentration based on a ratio of the conductivity of the water being discharged (blowdown) 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 ppm) 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 water 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

.

For cooling towers and evaporative condensers, conduct a one-time potable water analysis, in order to optimize cooling tower cycles. Measure at least the five control parameters listed in Table 1.

Table 1. Maximum concentrations for parameters in condenser water

Parameter Maximum level
Ca (as CaCO3) 1000 ppm
Total alkalinity 1000 ppm
SiO2 100 ppm
Cl- 250 ppm
Conductivity 2000 µS/cm

ppm = parts per million
µS/cm = micro siemens per centimeter

Calculate the number of cooling tower cycles by dividing the maximum allowed concentration level of each parameter by the actual concentration level of each parameter found in the potable makeup water. Limit cooling tower cycles to avoid exceeding maximum values for any of these parameters.

Table 2. Points for cooling tower cycles

Cooling tower cycles Points
Maximum number of cycles achieved without exceeding any filtration levels or affecting operation of condenser water system (up to maximum of 10 cycles) 1
Achieve a minimum 10 cycles by increasing the level of treatment in condenser or make-up water
OR Achieve the number of cycles for 1 point and use a minimum 20% recycled nonpotable water
2

Establishment

For cooling towers and evaporative condensers, conduct a potable water analysis within five years of submission for certification, measuring at least the five control parameters listed in Table 1.

Table 1. Maximum concentrations for parameters in condenser water

Parameter Maximum level
Ca (as CaCO3) 1000 ppm
Total alkalinity 1000 ppm
SiO2 100 ppm
Cl- 250 ppm
Conductivity 2000 µS/cm

ppm = parts per million
µS/cm = micro siemens per centimeter

Calculate the number of cooling tower cycles by dividing the maximum allowed concentration level of each parameter by the actual concentration level of each parameter found in the potable makeup water. Limit cooling tower cycles to avoid exceeding maximum values for any of these parameters.

Table 2. Points for cooling tower cycles

Cooling tower cycles Points (except data centers) Points (data centers)
Maximum number of cycles achieved without exceeding any filtration levels or affecting operation of condenser water system (up to maximum of 10 cycles) 2 2
Achieve a minimum 10 cycles by increasing the level of treatment in condenser or make-up water
OR Achieve the number of cycles for 1 point and use a minimum 20% recycled nonpotable water
3 4

Performance

None

Establishment

For cooling towers and evaporative condensers, conduct a potable water analysis within five years of submission for certification, measuring at least the five control parameters listed in Table 1.

Table 1. Maximum concentrations for parameters in condenser water

Parameter Maximum level
Ca (as CaCO3) 1000 ppm
Total alkalinity 1000 ppm
SiO2 100 ppm
Cl- 250 ppm
Conductivity 2000 µS/cm

ppm = parts per million
µS/cm = micro siemens per centimeter

Calculate the number of cooling tower cycles by dividing the maximum allowed concentration level of each parameter by the actual concentration level of each parameter found in the potable makeup water. Limit cooling tower cycles to avoid exceeding maximum values for any of these parameters.

Table 2. Points for cooling tower cycles

Cooling tower cycles Points (except data centers) Points (data centers)
Maximum number of cycles achieved without exceeding any filtration levels or affecting operation of condenser water system (up to maximum of 10 cycles) 2 2
Achieve a minimum 10 cycles by increasing the level of treatment in condenser or make-up water
OR Achieve the number of cycles for 1 point and use a minimum 20% recycled nonpotable water
3 4

Performance

None

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