24
Refrigeration System Checks
This unit is equipped with thermal expansion valves.
Ensure the hold-down bolts on the compressor are secure
and have not vibrated loose during shipment. Check
that the vibration grommets have been installed and
visually check all piping for damage and leaks and repair
if necessary. The entire system has been factory charged
and tested, making it unnecessary to field charge. Factory
refrigerant charge is shown on the unit’s nameplate.
To confirm charge levels or, if a leak occurs and charge
needs to be added to the system, it is recommended to
evacuate the system and recharge refrigerant to the unit’s
nameplate specifications. This unit has been rated in the
cooling mode at the AHRI rated conditions of: indoor (80°F
db/67°F wb) and outdoor (95°F db). While operating at this
condition, the superheat should range from 9°F to 11°F for
each refrigeration circuit measured at the suction service
port located near the compressor.
Start-Up Procedure and Checklist
Begin with power turned off at all disconnects.
1. Turn thermostat system switch to “Cool,” and fan
switch to “Auto” and turn temperature setting as high
as it will go.
2. Inspect all registers and set them to the normal open
position.
3. Turn on the electrical supply at the disconnect.
4. Turn the fan switch to the “ON” position. The blower
should operate after a 7 second delay.
5. Turn the fan switch to “Auto” position. The blower
should stop after a 60 second delay.
6.
Slowly lower the cooling temperature until first stage
COOL (LOW COOL) starts. The blower, both fans,
and first stage compressor should now be operating.
Allow the unit to run 10 minutes, make sure cool air is
being supplied by the unit.
7. Lower the cooling temperature further until second
stage COOL (HIGH COOL) starts. The blower, both
fans, and both compressors should now be operating.
Allow the unit to run 10 minutes, make sure cool air is
being supplied by the unit.
8. Turn the temperature setting to the highest position,
stopping the unit. The indoor blower will continue to
run for 60 seconds.
9. Turn the thermostat system switch to “OFF” and
disconnect all power when servicing the unit.
Refrigeration Sequence Check
With the disconnect switch open, remove the field
connected thermostat wire from terminal R on TB1
terminal block. Place a jumper across terminals R and
G, and across R and Y on TB1 terminal block. Close the
disconnect switch. The following operational sequence
should be observed.
1. Current through primary winding of transformer
TRANS1 energizes the 24-volt control circuit.
2. To simulate a mechanical call for cooling from the wall
thermostat, place a jumper across terminals R and Y1
of terminal block TB1.
3. UNIT WITH ECONOMIZER OPTION:
The
compressor circuit is interlocked through terminals
3 and 4 of the economizer module. If the outdoor air
enthalpy (temperature and humidity) is not suitable
for cooling, the economizer terminals will be closed
permitting compressor to be energized.
4. The belt drive blower contactor closes its contacts L1,
L2 and L3 to T1, T2 and T3 to provide power to the
supply fan motor.
5. Check supply fan rotation. If the supply fan is rotating
in the wrong direction, disconnect and lock off Single
Point Power Block. Do not attempt to change load
side wiring. Internal wiring is set at the factory to
assure that the supply fan and compressors all rotate
in the proper direction. Verification of correct supply
fan rotation at initial startup will also indicate correct
compressor rotation. Reconnect power and check for
proper operation.
6. Compressor contactor closes its contacts L1, L2
and L3 to T1, T2 and T3 to provide power to the
compressor motor COMP 1; COMP 2, if conditions
are correct. In addition, contactor C1 closes its
contact L3 to T3 , energizing the condenser fan motor.
WARNING
BURN HAZARD!
DO NOT TOUCH! DISCHARGE LINE MAY BE HOT!
7. Check that each compressor is operating correctly.
The scroll compressors in these units MUST operate
in the proper rotation. To ensure the compressors
are operating in the correct direction, check the
compressor discharge line pressure or temperature
after each compressor is started.
The discharge pressure and discharge line
temperature should increase. If this does not occur
and the compressor is producing an exceptional
amount of noise, perform the following checks.
• Ensure all compressors and the supply fan
motor are operating in the proper direction. If
a single motor is operating backwards, check
the power wiring for that motor and correct
any leads that have been interchanged at the
contactor or at the motor.
• If all of the motors are operating backward,
disconnect the unit power supply and lock
it in the “OFF” position. Switch two leads
of the power supply at the unit Single Point
Power Block. Reconnect power and check for
compressor and supply fan motor operation.
