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Fan Control
The following are fan control methods to reducing icing:
•
Variable Frequency Drives
: See
page 35
for information.
•
Multi-Speed Motors
: If the unit is equipped with 2-speed motors or BALTIGUARD™/
BALTIGUARD PLUS™ Fan System, operation at a lower speed may be sufficient to
prevent icing. The motor starter should include a minimum 15 second time delay
when switching from high to low speed.
•
Fan Cycling
: Set the controls to allow a maximum of six on-off cycles per hour. Cycle
the fan off for five minutes every 15 to 20 minutes for each cell. If ice continues to
build on the air intake, decrease the on-time. Observe the air intake of the unit at least
every four to eight hours.
•
Fan Reversal:
This procedure should be used only after the other methods of fan
control fail. If utilized, the fans should be run in reverse for no longer than 20 minutes
at no more than 50% speed, and the cooling tower should be observed during this
time. Before returning to normal operation, visually inspect the fan blades for ice
formation.
Basin Water and Internal Piping Freeze Protection
Cold Water Basin Protection
It is important to protect the basin and internal piping. The basin water could freeze when
the unit is shut-down and exposed to subfreezing ambient temperatures.
•
Remote Sump
: The ideal method of protection is a remote sump located in a heated
indoor space. When the circulating pump stops, the water in the connecting piping
will drain by gravity to this indoor sump.
•
Basin Heaters
: On applications without a remote sump, heat must be provided to the
cold water basin. Electrical immersion heaters or steam coils can provide the required
function. Contact your local BAC Representative for details.
•
Electric Water Level Control
: An electric water level control will maintain the proper
water level regardless of the thermal load or variations in make-up water supply
pressure. The two-position, slow closing solenoid valve provided with the BAC electric
water level control package also minimizes valve freezing problems (see
page 20
).
•
Heat Tracing
: Heat trace and insulate all exposed water piping including pump piping
below the overflow level and make-up water lines with electrical heater tape.
NOTE:
Modulating the water
flow rate to the unit is NOT a
recommended method of controlling
cooling capacity.
NOTE:
For remote sump
applications, the water level in
the basin of the equipment is a
function of the design flow rate,
the quantity, size and location
of the remote sump connection
and the pipe design between the
cooling tower and the remote sump.
Units installed on remote sump
applications are supplied without a
make-up connection.
Cold Weather Operation
Inspection & Maintenance
Fan Section Icing Protection
Temperature Setting
Fan Control
Basin Water and Internal Piping
Freeze Protection
Cold Water Basin Protection