GE GBSC0 Technical Service Manual page 41

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.
AC DC Condenser Fan Motor
The AC DC condenser fan motor is connected in
parallel with the compressor and evaporator fan
motor. The AC DC condenser fan motor utilizes
115 VAC and operates when the compressor and
evaporator fan motor are running.
DC Condenser Fan Motor
The DC 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.
EVAP FAN
COND FAN
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.
13.6 VDC
12.0 VDC
0 VDC
13.6 VDC
10.5 VDC
0 VDC
13.6 VDC
7.5 VDC
0 VDC
13.6 VDC
5.5 VDC
0 VDC
– 41 –
+12V RED
YELLOW
YELLOW/BLACK
WHITE/SILVER (COMM)
BLUE
Super High Speed (12.0 VDC measured)
High Speed (10.5 VDC measured)
Medium Speed (7.5 VDC measured)
Low Speed (5.5 VDC measured)