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START-UP
Initial Check
Do not attempt to start the condensing unit, even mo-
mentarily, until the following steps have been com-
pleted. Compressor damage may result.
1. Checkall auxiliary components, such asair-handling equip-
ment, and other equipment. Consult the manufacturer’s
instructions regarding any other equipment connected
to the condensing unit. If used, airflow switch must be
properly installed. See Fig. 8.
2. Backseat (open) compressor suction and discharge valves.
Close valves one turn to allowpressure to reach test gages.
3. Open liquid line service valve.
4. Set thermostat.
5. Check tightness of all electrical connections.
6. Compressor oil level should be visible in sight glass.
See Service, Oil Charge section on page 19.
7. Be sure unit isproperly leak tested,dehydrated, and charged.
See below.
8. Electrical power source must agree with nameplate
rating.
9. Crankcase heater must be firmly locked into compres-
sor crankcase. Be sure crankcase is warm (heater should
be on for 24 hours before starting compressor).
10. Be sure compressor floats freely on the mounting springs.
See Compressor Mounting section on page 2 and Fig. 3
for loosening compressor bolts.
Leak Test and Dehydration — Leak test the entire
refrigerant system by the pressure method described in the
Carrier Training Booklet; GTAC II, Module 4 - System
Dehydration.
Preliminary Charge — Refer to Carrier Training Book-
let; GTAC II, Module 5 for charging methods and proce-
dures. Charge system with approximately 25 lbs (11.3 kg) of
R-22 by the liquid charging method (charging through liq-
uid service valve), on the high side, and charging by weight.
Charge per Fig. 10-12.
Start Unit — Close field disconnect. Set thermostat above
ambient temperature so that there is no demand for cooling.
Now, only the crankcase heater is energized.After the heater
has been on for 24 hours, the unit can be started. If no time
has elapsed since the preliminary charge step has been com-
pleted, it is unnecessary to wait the 24-hour period.
Close the compressor circuit breaker, then reset the in-
door thermostat below ambient temperature, so that a call
for cooling is ensured.
NOTE: Do not use the compressor circuit breaker to start
and stop compressor, except in an emergency.
The start-up of the compressor can occur between 3 seconds
and approximately 5 minutes from the time the control cir-
cuit is energized due to the anti-short cycle feature of the
control module (CM).
Charge System — Actual start-up should be done only
under supervision of a qualified refrigeration mechanic. Re-
fer to charging charts.
See Fig. 10-12 for the particular unit being charged. Mea-
sure pressure at the liquid line service valve, being sure a
Schrader depressor is used if required. Also, measure liquid
line temperature as close to the liquid service valve as pos-
sible. Add or reduce charge until the pressure and tempera-
ture conditions of the charging charge curve are met. If liq-
uid pressure and temperaturepoint fall above curve, add charge.
If liquid pressure and temperature point fall below curve,
reduce the charge until the conditions match the curve.
Never charge liquid into the low-pressure side of sys-
tem. Do not overcharge. During charging or removal of
refrigerant, be sure indoor fan system is operating.
Operation — Refer to control circuit diagram on the unit,
or in the unit wiring book.
Control Module (CM) — The unit control module is
located in the control section of the control box. See
Fig. 9A or 9B. It performs several functions. The CM has a
built-in compressor anti-short-cycle timer which will not al-
low the compressor to restart until 5 minutes (ϩ90 seconds/
–75 seconds) have elapsed since the previous shutdown.
The compressor oil pressure is monitored through the CM.
The unit is allowed to remain operational as long as the oil
pressure safety switch (OPS) has not been open for more
than 2 minutes after the compressor has started. If after start-
up, the OPS is open for more than 2 minutes, the CM shuts
down the compressor and places the unit in a lockout con-
dition. The CM activates the fault indication circuit, and the
field-supplied unit service lamp is illuminated (if soequipped).
The unit cannot be restarted until power is interrupted at the
unit, resetting the CM. The 5-minute recycle time relay is
initiated.
The CM also monitors the high-pressure switch (HPS) and
compressor thermal protection. If at any time the HPS opens,
the CM shuts down the compressor and places the unit in a
lockout condition. The CM activates the fault indication cir-
cuit, and the field-supplied unit service lamp is illuminated
(if so equipped). The unit cannot be restarted until the HPS
is reset and until power is interrupted at the unit, resetting
the CM. The 5-minute recycle time relay is initiated.
If the unit shuts down on an automatic reset switch, such
as the low-pressure switch (LPS), the compressor will be al-
lowed to restart when the switch recloses and the CM anti-
short-cycle time has elapsed.
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