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W W W . B A L T I M O R E A I R C O I L . C O M . A U
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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.
• 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 unit
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
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.
• 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.