Page 14
Cooling Start−Up
IMPORTANT−The crankcase heater (standard on
some models) must be energized for 24 hours before
attempting to start compressor. Set thermostat so there
is no demand to prevent compressor from cycling.
Apply power to unit.
A−Preliminary Checks
1− Make sure that unit is installed in accordance with the
installation instructions and applicable codes.
2− Inspect all electrical wiring, both field and factory
installed, for loose connections. Tighten as required.
3− Check to ensure that refrigerant lines do not rub
against the cabinet or against other refrigerant lines.
4− Check voltage at disconnect switch. Voltage must
be within range listed on nameplate. If not, consult
power company and have voltage condition
corrected before starting unit.
5− Refer to unit diagram located on inside of
compressor access door for unit wiring.
6− Adjust blower belt or blower speed tap according to
HBlower Operation and Adjustments" section.
7− Make sure filters are in place before startEup.
B−Start−Up
1− Set fan switch to AUTO or ON and move system
selection switch to cool. Adjust thermostat to a
setting below room temperature to bring on the
compressor. Compressor will start and cycle on
demand from thermostat.
2− The refrigerant circuit is charged with HCFC−22
refrigerant. See unit rating plate for correct
amount of charge.
3− Refer to Cooling Operation and Adjustment section
for proper method to check refrigerant charge.
C−Three Phase Scroll Compressor Voltage Phasing
Three phase scroll compressors must be phased
sequentially to ensure correct compressor and blower
rotation and operation. Compressor and blower are
wired in phase at the factory
1− Observe suction and discharge pressures and
blower rotation on unit start−up.
2− Suction pressure must drop, discharge pressure
must rise, and blower rotation must match rotation
marking.
If pressure differential is not observed or blower rotation is
not correct:
3− Disconnect all remote electrical power supplies.
4− Reverse any two field−installed wires connected to
the line side of S48 disconnect or TB2 terminal strip.
Do not reverse wires at blower contactor.
5− Make sure the connections are tight.
Discharge and suction pressures should operate at
their normal startEup ranges.
D−Charging/Checking Charge
WARNING−Do not exceed nameplate charge under any
condition.
This unit is factory charged and should require no further
adjustment. If the system requires charge,
reclaim the
charge,
evacuate the system,
and
add required
nameplate charge.
NOTE − System charging is not recommended below 60
_
F
(15
_
C). In temperatures below 60
_
F (15
_
C),
the charge
must
be weighed into the system.
If weighing facilities are not available, or to check the
charge, use the following procedure:
IMPORTANT − Charge unit in standard cooling mode.
1− Attach gauge manifolds and operate unit in cooling
mode until system stabilizes (approximately five
minutes). Make sure all outdoor air dampers are closed.
2− Use a thermometer to accurately measure the
outdoor ambient temperature.
3− Apply the outdoor temperature to tables 12 through
14 to determine normal operating pressures.
4− Compare the normal operating pressures to the
pressures
obtained
from
the
gauges.
Minor
variations in these pressures may be expected due to
differences in installations. Significant differences
could mean that the system is not properly charged or
that a problem exists with some component in the
system.
Correct any system problems before
proceeding.
5− If discharge pressure is high, remove refrigerant from
the system. If discharge pressure is low, add
refrigerant to the system.
S
Add or remove charge in increments.
S
Allow the system to stabilize each time refrigerant is
added or removed.
6− Use the following subcooling method along with the
normal operating pressures to confirm readings.
