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Fan Control
Reduce the unit capacity by cycling the fans, thus modulating the airflow through the unit. Rapid on-off cycles can cause
induction fan motors to overheat. For induction motors, set the controls to allow a maximum of six on-off cycles per hour. EC
motors will self-limit fan speed to prevent overheating. Periodically, cycle the fans off to prevent ice formation and/or to melt ice
that accumulates on the equipment.
The following are fan control methods:
•
Variable Frequency Drives and EC motors: VFDs and EC motors offer the most precise method of capacity control by
modulating fan motor speed. When using them, avoid operating at or near resonant speeds. Units with VFDs require
premium efficient/inverter duty motors.
•
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.
NOTE: Modulating the water flow rate to the unit is NOT a recommended method of controlling
cooling capacity.
Dry Operation
One method to prevent icing is dry operation. Dry operation of the unit protects fans from ice formation due to mist and splash
from the basin. The water in the 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
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 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 28).
•
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: 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.
Vertex™ Evaporative Condenser Operation & Maintenance Manual – Cold Weather Operation
Page | 37
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