Basin Water And Internal Piping Freeze Protection - BAC FXV-0806-12D Series Operation & Maintenance Manual

Fan Control
Reduce the unit capacity by cycling the fans, thus modulating the airflow through the
unit. Rapid on-off cycles can cause the fan motor to overheat. Set the controls to allow
a maximum of six on-off cycles per hour. Periodically, cycle the fans off to prevent ice
formation and/or to melt ice that accumulates on the combined inlet shields.
The following are fan control methods:
• Variable Frequency Drives: VFDs offer the most precise method of capacity control by
modulating fan motor speed. When using VFDs, avoid operating at or near resonant
speeds. Units with VFDs require premium efficient/inverter duty motors.
• 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: 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 and the unit should be observed during this time. Before returning to normal
operation, visually inspect the fan blades for ice formation
Dry Operation
One method to prevent icing is dry operation. Dry operation of the evaporative condenser
protects fans from ice formation due to mist and splash from the cold water basin. The
water in the cold water basin must be drained in dry operation. For dry operation switch
points and recommendations, contact your local BAC representative.

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 shutdown 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 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 24).
• 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.
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