5
Operation and Maintenance Instructions
15. Closed hydronic systems connected to either a closed-
circuit cooler or dry cooler should be pre-cleaned and
flushed to remove debris, grease, flash rust, oil, and other
suspended solids prior to operation. Evapco recommends
the use of inhibitor chemistry or inhibited glycol to
minimize corrosion and scale during normal operation.
EVAPCO recommends a minimum of 25% inhibited glycol
to minimize corrosion.
For eco-WE & eco-W with optional controls, see controls O&M
for proper start up procedure.
After the unit has been energized, check the following:
1. Adjust mechanical float valve as required to the proper
water level.
2. Unit basin should be filled to the proper operating level.
See “Recirculating Water System Operating Levels”
section for more details.
3. Verify fan is rotating in proper direction.
4. Start the spray water pump and check for proper rotation
as indicated by the arrow on the front cover.
5. Measure voltage and current on all three power leads of
pump and fan motor. The current should not exceed the
motor nameplate full load amp rating taking the service
factor into account.
6. Adjust bleed valve to proper flow rate. Consult your
qualified water treatment company to fine tune the
minimum bleed necessary, see “Water Treatment and
Water Chemistry” section.
7. See fan and pump motor manufacturer maintenance
and long term storage instructions for more detailed
information. The motors should be lubricated and serviced
in accordance with manufacturers instructions.
Basic Closed Circuit Cooler / Condenser
Sequence of Operation for Wet or
Evaporative Mode
System Off / No Load
The system pumps and fans are off. If the basin is full of
water a minimum basin water temperature of 40ºF (4°C) must
be maintained to prevent freezing. This can be accomplished
with the use of optional basin heaters. See the “Cold Weather
Operation” section of this bulletin for more details on cold
weather operation and maintenance.
System/Condensing Temperature Rises
The recirculation pump turns on. The unit will provide
approximately 10% cooling capacity with only the pump
running. If the unit has positive closure dampers they should
be fully opened before the pumps turn on.
If the system temperature continues to rise, the unit fan is
cycled on. For a variable speed controller, the fans are turned
on to minimum speed. See the “Fan System – Capacity
Control” section of this bulletin for more details on fan speed
control options. If the system temperature continues to rise,
then the fan speed is increased as required, up to full speed.
NOTE: During sub-freezing weather the minimum
recommended speed for variable speed controllers is 50%.
ALL FANS IN OPERATING CELLS OF MULTIPLE CELL UNITS
MUST BE CONTROLLED TOGETHER TO PREVENT ICING ON
THE FANS.
System/Condensing Temperature Stabilizes
Control the leaving fluid temperature (closed circuit coolers)
or condensing temperature (evaporative condensers) by
modulating the fan speeds with variable speed drives or by
cycling fans on and off with single or two-speed drives.
System/Condensing Temperature Drops
Decrease the fan speed, as required.
System Off / No Load
The system pump turns off. The starter interlock will energize
any optional basin heaters in cold weather.
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.
Dry Operation
During colder winter months it is possible to turn off the spray
pump, drain the cold water basin, and just cycle the fans. Be
sure to leave the basin drain open during this time to prevent
collection of rain water, snow, etc. If the unit has positive
closure dampers they should be fully opened before the fans
turn on. If dry operation will be used on a centrifugal fan,
forced draft unit, be sure to verify that the motor and drives
have been properly sized to handle the reduction in static
pressure experienced when the spray water is turned off.
NOTE: Minimum control point for process fluid should never
be lower than 42º F (6°C).
NOTE: When a unit is provided with a discharge damper
assembly, the control sequence should cycle the dampers
open and closed once a day regardless of capacity
requirements to prevent the assembly from seizing. The fan
motor should be shut off whenever the dampers are closed.
NOTE: ESW4 or PHC-E product lines should not operate dry.
NOTE: The eco-ATW/eco-ATWE sequence of operation is
unique and is explained in detail in the Sage2, Sage3 Panel
Control Manual
To Next Page
Loading...
Need help?
General
