Unit
Setup
(SCR) Motor Speed Control Adjustment Procedure.
In order to make units more convenient and efficient to balance, an SCR (silicone control rectifier) is provided as standard on all
The SCR is located on the side of the fan control box. To adjust the speed of the motor, the external knob must be rotated either clockwise or counterclockwise depending on the desired speed adjustment.
There is an internal potentiometer (Figure 14) setting on the SCR controller that can be accessed by removing the control box cover. This internal potentiometer is set at the factory to the specific motor voltage.
It may be necessary to adjust this in the field depending on the building’s power factor.
WARNING
HazardousVoltage!
Disconnect all electric power, including remote disconnects before servicing. Follow proper lockout/tagout proce- dures to ensure the power cannot be inadvertently energized. Failure to disconnect power before servicing could result in death or serious injury.
Figure 16 – SCR
Figure 17 – Internal Potentiometer
Max
120 v
208 v–
277 v
347 v
DO NOT SET THIS
POTENTIOMETER
BELOW THE VOLTAGE
OF THE FAN MOTOR.
NOTE: Do not set this potentiometer below the voltage of the fan motor.
Electrically Commutated Motor (ECM)
Trane offers an energy efficient ECM motor as a motor option. Balancing of an ECM motor is accomplished through electronic control adjustments on the ECM control board (see Figure 15). Potentiometer settings for a multitude of CFM settings are given in Charts
CFMsetting = CFMmin + {(Potentiometer Setting) x [(CFMmax - CFMmin)/100]}
There is an LED on the ECM control board, which will blink one time for every 100 CFM of motor setting. For example, the LED on a unit set for 790 CFM will blink 7 times. The LED on a unit set for 800 CFM will blink 8 times.
NOTE:This feature only verifies that the CFM is set properly. This feature does not indicate at what speed the motor is actually running.
The ECM must be “load tested.” In other words, the fan must be connected to properly test the ECM.
Figure 18 – ECM Control Board
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