AAON LL-540 - Manual (Page 55)

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should be made with the circulation
pump on and fans off.
Mist Eliminators
The mist eliminators must be correctly
positioned when they are replaced during
cleaning or service.
Air Inlet
Inspect the air inlet louvers and mist
eliminators into the condenser section on a
monthly basis to remove any paper, leaves
or other debris that may block the airflow.
Stainless Steel Base Pan
The base pan under the tube bundles is
stainless steel and may sometimes become
tarnished due to contamination. These
surfaces should be inspected yearly to
ensure
they remain clean of any
contamination that may result in damage.
Any surfaces that show contamination
should be cleaned ONLY with a commercial
stainless steel cleaner to restore the initial
appearance.
Propeller Fans and Motors
The fans are directly mounted on the motor
shafts and the assemblies require minimal
maintenance except to assurance they are
clear of dirt or debris that would impede the
airflow.
Recommended Annual Inspection
In addition to the above maintenance
activities, a general inspection of the unit
surface should be completed at least once a
year. Remove spray header and flush out.
Cleaning
Mechanical cleaning, including pressure
washing, should never be performed as
surfaces and seals could be damaged.
Chemical cleaning that is safe for stainless
steel, copper, aluminum, ABS plastic and
PVC is the only acceptable means of
cleaning the evaporative condenser. A
proper water treatment program should
reduce cleaning needs.
Water Quality
Table 12 - Recirculating Water Quality
Guidelines
PH 6.5 to 9.0
Hardness as CaCO
3
500 PPM Max
Alkalinity as CaCO
3
500 PPM Max
Total Dissolved
Solids
2000 PPM Max
Chlorides as NaCl 1500 PPM Max
Sulfates 750 PPM Max
Cycles of concentration (the ratio of
dissolved solids in recirculated water to
dissolved solids in makeup water), should be
determined and monitored frequently by a
competent water treatment expert.
To limit cycles of concentration to maintain
the above guideline, it is necessary to
“bleed” a certain portion of the recirculated
water. This is achieved automatically with a
solenoid valve actuated by a conductivity
meter set at the desired conductivity
corresponding to the desired cycles of
concentration. It should be noted that these
are guidelines and even though these
individual values are met, under certain
conditions the water quality can be
aggressive. For example, water with very
low alkalinity and levels of chlorides and
sulfates
approaching maximum
recommended levels can be corrosive.
All AAON evaporative-cooled condensers
are furnished with a bleed system fitting and
valve to continuously remove a small
portion of the recirculated water to keep the
water quality within the above listed
parameters. This device is located on the
discharge side of the pump. It is important to
note that since “bleed” rate is a function of
evaporation rate (i.e., amount of heat