WEc3: Cooling Tower and Process Water Use – Above Green

(1-2 points)

Intent

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

Requirements

Option 1. Cooling Tower Water Use (1-2 points except CS, 1-3 points CS)

For cooling towers and evaporative condensers, conduct a one-time potable water analysis, 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 maximum 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 analysis. 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
(all except CS)

Points (CS)

Maximum number of cycles achieved without exceeding any
filtration levels or affecting operation of condenser water
system

Meet the maximum calculated number of cycles to earn 1
point, and increase the number of cycles by a minimum of
25% by increasing the level of treatment and/or maintenance
in condenser or make-up water systems

Meet the maximum calculated number of cycles to earn 1
point and use a minimum 20% recycled nonpotable water

Meet the maximum calculated number of cycles to earn 1
point, and increase the number of cycles by a minimum of
30% by increasing the level of treatment and/or maintenance
in condenser or make-up water systems

Meet the maximum calculated number of cycles to earn 1
point and use a minimum 30% recycled non-potable water

Minimum percentage recycled non-potable water used in cooling tower makeup should be based on water use during the month with the highest demand for make-up water.

Projects whose cooling is provided by district cooling systems are eligible to achieve Option 1 if the district cooling system complies with the above requirements.

Option 2. No Cooling Tower (2 points)

For projects without cooling towers or evaporative condensers, projects may earn full credit if all conditions are met:

the baseline system designated for the building using ASHRAE 90.1-2016 Appendix G Table G3.1.1 includes a cooling tower (systems 7 & 8)
the project design case does not include a cooling tower
the design case mechanical system does not use the latent heat of the evaporative cooling of water.
the project does not receive any cooling from a District cooling system

All other system types are ineligible for credit.

Option 3. Process Water Use (1-2 points except CS, 1-3 points CS)

Demonstrate that the project is using minimum 20% recycled alternative water to meet process water demand for 1 point, or using minimum 30% recycled alternative water to meet process water demand for 2 points. Ensure that recycled alternative water is of sufficient quality for its intended end use.

Minimum percentage of recycled alternative water used should be based on water use during the month with the highest water demand.

Process water uses eligible for achievement of Option 3 must represent at least 10% of total building water use. Eligible subsystems may include:

Boilers
Humidification systems
Other subsystems using process water

Projects whose cooling is provided by district cooling systems are eligible to achieve Option 3 if the district cooling system complies with minimum thresholds for recycled alternative water use.

CS projects:
Demonstrate that the project is using minimum 20% recycled alternative water to meet process water demand for 1 point, using minimum 30% recycled alternative water to meet process water demand for 2 points, or using minimum 40% recycled alternative water to meet process water demand for 3 points. Ensure that recycled alternative water is of sufficient quality for its intended end use.