TM 9-4120-407-14
3-6. INSTALLATION INSTRUCTIONS. (Cont)
b. Connecting Ground and Power Cable.
(1) Install a 10 AWG (minimum) ground wire between air conditioner cabinet and an adequate earth
ground.
(2) Determine the length of power cable required and fabricate per Appendix F, Figure F-4.
VOLTAGES USED IN THIS EQUIPMENT CAN KILL.
The following test is conducted with the power on. Exercise extreme
caution to avoid injury.
If a miswired power cable is connected to the air conditioner, unit
damage can result.
(3) Connect power cable to a source of 208 volt, 3 phase, 50/60/400 hertz power but do not connect
power cable to air conditioner. Check voltage at power cable connector per the following:
(a) Using a multimeter, check for AC voltage between connector pin D and a good chassis ground.
If any voltage is measured, disconnect power cable and check the power source for incorrect
wiring. Correct any problem with power source, connect power cable, and re-check for voltage.
(b) Check voltage between remaining pins and compare readings to those listed in Table 3-1. If
voltage measured is more than 10 volts above or below those listed, disconnect power and
correct problem at power source.
Table 3-1. Power Cable Connector
Measure
To Pin:
A
B
C
From Pin:
D
120
208
208
N/A
A
208
N/A
208
120
B
120
N/A
208
208
C
N/A
120
120
120
D
(4) Turn MODE selector rotary switch to OFF RESET position.
The air conditioner motor controller creates a momentary short circuit
when power is applied to it. Damage to the connector and power
cable pins can result if it is not isolated when the power cable is
Connected.
(5) Place circuit breaker handle in OFF (down) position to isolate the motor controller.
(6) Route power cable to the air conditioner through the return air opening or outside panel as
appropriate and connect.
(7) Place the circuit breaker handle in the ON (up) position.
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