– 40 –
The rear access cover must be tightly
fi
tted to
prevent air from being exhausted directly out of the
rear of the machine compartment, bypassing the
compressor.
The condenser fan is mounted with screws to a fan
shroud and mounting bracket that is attached to
the condenser.
Condenser fan speed corresponds with compressor
speed (low, medium, high) to minimize pressure
variations in the sealed system except when the
freezer temperature is 20°F above the set point. If
this condition exists (such as during initial startup),
the condenser fan operates at super high speed
while the compressor operates at medium speed.
The speed of the fan is controlled by the voltage
output from the main control board. Voltage output
from the control board to the fan is 13.6 VDC;
however, to regulate the speed of the fan, the main
control board uses pulse width modulation (PWM).
When operating, voltage is sent in pulses (much like
a duty cycle) as opposed to an uninterrupted
fl
ow.
This pulsing of 13.6 VDC produces effective voltage
being received at the motor, which is equivalent to a
reduction in voltage.
Fan speed is selected and maintained by the main
control board regulating the length and frequency
of the 13.6 VDC pulse.
Temperature can cause some fan speed variation.
Fan speed can vary +/- 5%, depending on the
temperature, with higher temperatures causing
slightly higher speeds.
Condenser fan speed is controlled by Pulse Width
Modulation (PWM), the same method used to control
fan speeds for the evaporators.
High Speed (10.5 VDC measured)
Medium Speed (7.5 VDC measured)
Low Speed (5.5 VDC measured)
10.5 VDC
7.5 VDC
5.5 VDC
13.6 VDC
0 VDC
0 VDC
0 VDC
13.6 VDC
13.6 VDC
Super High Speed (12.0 VDC measured)
12.0 VDC
13.6 VDC
0 VDC
BLUE
WHITE/SILVER (COMM)
YELLOW/BLACK
YELLOW
+12V RED
COND FAN
EVAP FAN
RED
YELL
OW
WHITE
RED
YELL
OW
BL
UE
WHITE
J2-1
J2-3
J2-4
J2-5
J2-8
MAIN C
ONTROL BO
ARD
