Manual 2100-670I
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conditions become unfavorable for optimized cooling,
the system will change to mechanical cooling only.
When this occurs, the fan speed will remain at normal
speed for 2 minutes, allowing for the damper blade to
fully close. After the 2-minute period, the condenser
fan speed may be reduced to optimize head pressures.
During optimized cooling, all fan speed control will be
handled by the low ambient controls and high pressure
controls if system pressures were to get out of range.
High Pressure Control
Condenser Fan Speed
When the liquid pressure reaches 550 PSI, the
condenser fan will speed up, moving as much air as
possible in an attempt to reduce system pressures. The
condenser fan will operate at increased speed until the
liquid pressure reaches 450 PSI. At this point, the fan
will return to normal operating speed.
Second Stage Drop Out
If the liquid pressure reaches 620 PSI, the second
stage of cooling will be disabled for 2 minutes to
reduce the required condenser airflow. After 2 minutes,
if the pressure is less than the pressure cutout, it will
resume stage 2 operation.
Low Ambient Control
At low ambient outdoor air temperatures, the fan motor
will cycle as a means of controlling the system's head
pressure to protect the system from evaporator coil
freeze conditions. The process for this system is as
follows: If the liquid pressure falls below 250 PSI, the
condenser fan will turn off. The fan will remain off
while the compressor remains running, allowing the
head pressure to build up. Once the liquid pressure
reaches 350 PSI, the fan will then turn back on at
the appropriate speed. At lower ambient outdoor
temperatures, this may cycle regularly as normal
operation. In some cases, in higher wind prone areas,
the condenser fan may stay off for prolonged durations
due to low liquid pressures.
Additional Condenser Fan Alarms
Dirty Condenser Coil Alarm
The unit will continuously monitor system conditions
to determine if the condenser coil is dirty or blocked.
If the system monitors three consecutive cooling
cycles that indicate a dirty condenser coil, an alarm
will be generated. This alarm is a notification and will
automatically reset when conditions are no longer
present. The end user has the ability to adjust how
FIGURE 39
Condenser Fan Speed Control
