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Unit Start Up
8. Once the configuration for the components is complete, press the NEXT key until the LCD
displays the “Start test in __Sec.” screen. Press the + key to designate the delay before the test
is to start. This service test will begin after the TEST START key is pressed and the delay
designated in this step has elapsed. Press the ENTER key to confirm this choice.
9. Press the TEST START key to start the test. Remember that the delay designated in step 8 must
elapse before the system will begin to operate.
10. It is very important to review and follow the Electrical Phasing procedure described in the
startup procedure of the IOM. If the compressors are allowed to run backward for even a very
short period of time, internal compressor damage may occur and compressor life may be
reduced. If a scroll compressor is rotating backwards, it will not pump, make a loud rattling
sound and low side shell gets hot. Immediately shut off the unit. If the phasing is incorrect,
interchange any two compressor leads to correct the motor phasing.
11. Press the STOP key at the Human Interface Module in the unit control panel to stop the
compressor operation.
12. Repeat steps 5 through 11 for each compressor stage and the appropriate condenser fans.
Refrigerant Charging
1.
Attach a set of service gauges onto the suction and discharge gauge ports for each circuit. Refer
to
for the various compressor locations.
2. Open the Human Interface access door, located in the unit control panel, and press the SERVICE
MODE key to display the first service screen. Refer to the latest edition of the programming
manual for CV or VAV applications for the SERVICE TEST screens and programming
instructions.
3. Use
Table 35, p. 108
to program the following system components for the number 1
refrigeration circuit by scrolling through the displays;
Supply Fan (On)
–
OCC/UNOCC Relay (Unoccupied for VAV units)
–
All Compressors for each circuit (On)
–
Condenser Fans for each circuit (On)
4. Once the configuration for the components is complete, press the NEXT key until the LCD
displays the “Start test in __Sec.” screen. Press the + key to designate the delay before the test
is to start. This service test will begin after the TEST START key is pressed and the delay
designated in this step has elapsed. Press the ENTER key to confirm this choice.
5. Press the TEST START key to start the test. Remember that the delay designated in step 4 must
elapse before the system will begin to operate.
6. After all of the compressors and condenser fans for the number 1 circuit have been operating
for approximately 30 minutes, observe the operating pressures. Use the appropriate pressure
curve in
to determine the proper operating pressures. For
superheat and subcooling guidelines, refer to “Thermostatic Expansion Valves and Charging
by Subcooling” at the end of this section.
Note:
Do Not release refrigerant to the atmosphere! If adding or removing refrigerant is required,
the service technician must comply with all Federal, State and local laws. Refer to general
service bulletin MSCU-SB-1 (latest edition).
7.
Verify that the oil level in each compressor is correct.
8. Press the STOP key at the Human Interface Module in the unit control panel to stop the system
operation.
9. Repeat steps 1 through 8 for the number 2 refrigeration circuit.
