GE GBSC0 Technical Service Manual

– 41 –The rear access cover must be tightly fitted toprevent air from being exhausted directly out of therear of the machine compartment, bypassing thecompressor.The condenser fan is mounted with screws to a fanshroud and mounting bracket that is attached tothe condenser.DC Condenser Fan MotorThe DC condenser fan speed corresponds withcompressor speed (low, medium, high) to minimizepressure variations in the sealed system exceptwhen the freezer temperature is 20°F above the setpoint. If this condition exists (such as during initialstartup), the condenser fan operates at super highspeed while the compressor operates at mediumspeed.The speed of the fan is controlled by the voltageoutput from the main control board. Voltage outputfrom the control board to the fan is 13.6 VDC;however, to regulate the speed of the fan, the maincontrol board uses pulse width modulation (PWM).AC DC Condenser Fan MotorThe AC DC condenser fan motor is connected inparallel with the compressor and evaporator fanmotor. The AC DC condenser fan motor utilizes115 VAC and operates when the compressor andevaporator fan motor are running.Temperature can cause some fan speed variation.Fan speed can vary +/- 5%, depending on thetemperature, with higher temperatures causingslightly higher speeds.Condenser fan speed is controlled by Pulse WidthModulation (PWM), the same method used to controlfan speeds for the evaporators.High Speed (10.5 VDC measured)Medium Speed (7.5 VDC measured)Low Speed (5.5 VDC measured)10.5 VDC7.5 VDC5.5 VDC13.6 VDC0 VDC0 VDC0 VDC13.6 VDC13.6 VDCSuper High Speed (12.0 VDC measured)12.0 VDC13.6 VDC0 VDCBLUEWHITE/SILVER (COMM)YELLOW/BLACKYELLOW+12V REDCOND FAN EVAP FANREDYELLOWWHITEREDYELLOWBLUEWHITEJ2-1 J2-3 J2-4 J2-5 J2-8MAIN CONTROL BOARDWhen operating, voltage is sent in pulses (much likea duty cycle) as opposed to an uninterrupted flow.This pulsing of 13.6 VDC produces effective voltagebeing received at the motor, which is equivalent to areduction in voltage.Fan speed is selected and maintained by the maincontrol board regulating the length and frequencyof the 13.6 VDC pulse.