Bleed-Off Valve; Pump (When Supplied); Coils; Evaporative Coil(S) - EVAPCO ATC-E Operation And Maintenance Instruction Manual

Bleed-Off Valve

The bleed-off valve, whether factory or field installed, must be checked weekly to make sure it is functioning and set properly . Keep
the bleed-off valve wide open unless it has been determined that it can be set partially open without causing scaling or corrosion .

Pump (When Supplied)

The pump and pump motor should be lubricated and serviced in accordance with the pump manufacturer's instructions .
The recirculation pump should not be used as a means of capacity control, and should not be cycled frequently . Excessive cycling
can lead to scale build-up, and reduce wet and dry performance .

Coils

Contact Evapco in case of damage to the pressure vessel . Do not affect the integrity of the pressure vessel without approval of
Evapco .

Evaporative Coil(s)

Check coil surface periodically, but at least twice a year . Inspect the coil surface for scale and/or corrosion .
Dry Coils (optional)
Depending on outdoor conditions and unit type, the dry coil should be inspected and cleaned at least twice a year . If the unit is
located near trees, construction, etc ., the required cleaning may be more frequent . The coil should be visually inspected monthly
along with inlet louvers and inlet screens .
The best cleaning solution for the dry coil is plain water . If the coil has maintained and cleaned at regular intervals, water is
sufficient to remove dirt and debris from the fins . Heavy build up on the exterior of the fins can be removed with a brush . If a
pressure washer is used, make sure the equipment is set to a low pressure setting and that the nozzle is set to the fan spray, not
stream, otherwise damage to the fins could result .
Note: for the eco-ATW(E), please consult the Sage

Water Treatment and Water Chemistry

Proper water treatment is an essential part of the maintenance required for evaporative cooling equipment . A well designed and
consistently implemented water treatment program will help to ensure efficient system operation while maximizing the equipment's
service life . A qualified water treatment company should design a site specific water treatment protocol based on equipment
(including all metallurgies in the cooling system), location, makeup water quality, and usage .

Bleed or Blowdown

Evaporative cooling equipment rejects heat by evaporating a portion of the recirculated water into the atmosphere as warm,
saturated discharge air . As the pure water evaporates it leaves behind the impurities found in the system's makeup water and any
accumulated airborne contaminants . These impurities and contaminants, which continue to recirculate in the system, must be
controlled to avoid excessive concentration which can lead to corrosion, scale, or biological fouling .
Evaporative cooling equipment requires a bleed or blowdown line, located on the discharge side of the recirculating pump, to
remove concentrated (cycled up) water from the system . EVAPCO recommends an automated conductivity controller to maximize
the water efficiency of your system . Based on recommendations from the water treatment company, the conductivity controller
should open and close a motorized ball or solenoid valve to maintain the conductivity of the recirculating water . If a manual valve
is used to control the rate of bleed it should be set to maintain the conductivity of the recirculating water during periods of peak
load at the maximum level recommended by the water treatment company .
Galvanized Steel – Passivation
'White Rust' is a premature failure of the protective zinc layer on hot dip or mill galvanized steel which can occur as a result of
improper water treatment control during the start-up of new galvanized equipment . The initial commissioning and passivation
period is a critical time for maximizing the service life of galvanized equipment . EVAPCO recommends that the site specific
water treatment protocol includes a passivation procedure which details water chemistry, any necessary chemical addition, and
visual inspections during the first six (6) to twelve (12) weeks of operation . During this passivation period, recirculating water pH
should be maintained above 7 .0 and below 8 .0 at all times . Since elevated temperatures have a harmful effect on the passivation
process, the new galvanized equipment should be run without load for as much of the passivation period as is practical .
The following water chemistry promotes the formation of white rust and should be avoided during the passivation period:
1 . pH values in the recirculating water greater than 8 .3 .
2 . Calcium hardness (as CaCO
3 . Anions of chlorides or sulfates greater than 250 ppm in the recirculating water .
4 . Alkalinity greater than 300 ppm in the recirculating water regardless of pH value .
Changes in water chemistry control may be considered after the passivation process is complete as evidenced by the galvanized
surfaces taking on a dull gray color . Any changes to the treatment program or control limits should be made slowly, in stages
while documenting the impact of the changes on the passivated zinc surfaces .
and Sage manual .
2 3
) less than 50 ppm in the recirculating water .
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Operation and Maintenance Instructions
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