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Chemical Treatment Requirements
Chemical treatment programs must meet the following requirements:
• The chemicals must be compatible with the specific unit materials of construction.
• BAC generally discourages acid dosing as means of scale control. Should acid dosing
be utilized, the acid should be injected at a point in the system where total mixing and
dilution occur, such as the water treatment connections in the spray water basin.
• Units shipped with connections for optional water treatment (provided by others) will
have (2) 3/4” FPT connections on either side of the cold water basin.
• When chlorine is added to the system, free residual chlorine should not exceed 1 ppm,
except as noted in start-up section (
page 6
) and the shutdown section (
page 19)
.
Exceeding this limit may accelerate corrosion.
No Passivation Required
Passivation is the formation of a protective, passive, oxide layer on galvanized steel
surfaces. However, since the Nexus
®
Modular Hybrid Cooler is only available with
components protected by either Thermosetting Polymer and / or stainless steel, there are
no exposed galvanized surfaces, so passivation is not required.
Biological Control
• The warm, oxygen and nutrient rich environment inside evaporative cooling equipment
provides an ideal environment for the growth of algae, slime, and other micro-
organisms. Uncontrolled, this can reduce heat transfer, promote corrosion, and
promote the growth of potentially harmful organisms such as
Legionella
.
•
To avoid biological contamination and minimize the risk of
Legionella,
initiate the
biocide treatment program at start-up and continue on a regular basis thereafter in
accordance with the treatment supplier’s instructions.
• Bleed/blowdown or chemical treatment used for corrosion and scale control alone is
not adequate for control of biological contamination.
• Introduce solid or granular biocides through a chemical “pot” feeder installed in
parallel with the system circulating pump(s) using a separate chemical feed pump.
Diluted liquid biocides may be added directly to the spray water basin through the
water treatment connections.
NOTE:
ASHRAE Guideline 12:
Minimizing the Risk of Legionellosis
Associated with Building Water
Systems is available for free from
www.BaltimoreAircoil.com.