Carrier 38AE - Manual (Page 7)

Head Pressure Control by means of/an cycling is a
standard feature of 38AE012-016 units. The no. 2 fan cy­
cles in response to changes in liquid pressure. The switch
cycles the fan off at 126 ± 4 psig (869 ± 28 kPa) as pres­
sure decreases, and cycles back on at 257 (-1-5, -0) psig
(1772 [-f 103, -0] kPa).
CONTROL
SET POINT
ADJUSTMENT
NUT
PRESSURE
DIFFERENTIAL
ADJUSTMENT
SCREW
VALVE BODY
BYRASS
PISTON
DIFFERENTIAL SCREW'
SEALING CAP
(CAP MUST BE REPLACED
TO PREVENT REFRIGERANT LEAKAGE)
Fig. 7 — Compressor Capacity Controi Unloader
Time Guard® II Circuit provides for a delay of ap­
proximately 5 minutes before restarting compressor after shut­
down from safety device action.
On start-up, the Time Guard II timer causes a delay of
approximately 3 seconds after thermostat closes.
On compressor shutdown, the timer recycles for approx­
imately 5 minutes. During this time, the compressor cannot
restart.
Refer to Fig. 8 and to label diagram on unit.
TIME DELAY TIMING SEQUENCE
T1-T2
---------- RUNNING TIME---------- »■
p«------ 3SEC ------------------------- »■ 5 MIN
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DENOTES CLC6ED CONTACTS
Fig. 8 — Timer Sequence Chart
Winter-Start Control (If Required) - install Ac­
cessory Package 38AE900021.
Crankcase Heater prevents refrigerant migration and
compressor oil dilution during shutdown whenever com­
pressor is not operating. It is wired into the control circuit,
cycling with the compressor, off when compressor is run­
ning, and on when compressor cycles off.
Both compressor service valves must be closed when­
ever crankcase heater is deenergized for more than 6 hours.
The crankcase heater is operable as long as the control cir­
cuit is energized.
Outdoor Fans — Each fan is supported by a formed-
wire mount bolted to the fan deck and covered with a wire
guard. The exposed end of the motor shaft is covered with
a rubber boot. In case a fan motor must be repaired or re­
placed, be sure the rubber boot is put back on when the fan
is reinstalled and be sure the fan guard is in place before
starting the unit. Figure 9 shows the proper position of the
mounted fan. Fan motors have permanently lubricated
bearings.
Lubrication
FAN MOTORS have sealed lubrication bearings. No pro­
visions for lubrication are made.
COMPRESSOR has its own oil supply. Loss of oil due to a
leak in the system should be the only reason for adding oil
after the system has been in operation. See Oil Charge
section.