9. Remove the jumper from around the contacts of the OAT
if installed in Step 6. Remove the jumper from termi-
nals T and T1 installed in Step 7.
10. If the cooling mode was simulated to operate the unit
in Step 4, remove the jumper and reconnect the ther-
mostat wires to terminals Y1 and Y2.
VI. POWER FAILURE
Dampers have a spring return. In event of power failure, damp-
ers will return to fully closed position until power is restored.
Do not manually operate economizer motor.
VII. REFRIGERANT CHARGE
Amount of refrigerant charge is listed on unit nameplate and
in Table 1. Refer to Carrier GTAC II; Module 5; Charging,
Recovery, Recycling, andReclamationsection for charging meth-
ods and procedures.
Unit panels must be in place when unit is operating during
charging procedure.
A. No Charge
Use standard evacuating techniques. After evacuating sys-
tem, weigh in the specified amount of refrigerant (refer to
Table 1).
B. Low Charge, Cooling
Using appropriate cooling charging chart (see Fig. 30 and 31),
add refrigerant until conditions of the appropriate chart are
met. Note that charging charts are different from those nor-
mally used. Charts are based onchargingunitsto correct super-
heat for various operating conditions. An accurate pressure
gage and temperature sensing device are required. Connect
temperature sensing device to service port on suction line and
insulate it so that outdoor ambient temperature does not af-
fect reading. Indoor-air cfm must be within normal operating
range of unit.
C. To Use Cooling Charging Chart
Take outdoor ambient temperature and read the suction pres-
sure gage. Refer to appropriate chart to determine correct
suction temperature. If suction temperature is high, add
refrigerant. If suction temperature is low, carefully recover
some of the charge. Recheck suction pressure as charge is
adjusted.
Example (Fig. 31)
Outdoor Temperature ...........................85F
Suction Pressure .............................70psig
Suction Temperature should be ...................60F
(Suction Temperature may vary±5F)
D. Low Charge, Heating
If outdoor ambient temperature is above 40 F, operate unit
on cooling and refer to Low Charge, Cooling section above. If
outdoor ambient is below 40 F, evacuate system and weigh in
specified amount of refrigerant. (Refer to Table 1.)
VIII. FILTER DRIER
Replace whenever refrigerant system is exposed to
atmosphere.
IX. PROTECTIVE DEVICES
A. Compressor Protection
Overcurrent
Each compressor has one manual reset, calibrated trip, mag-
netic circuit breaker. Do not bypass connections or increase
the size of the circuit breaker to correct trouble. Determine
the cause and correct it before resetting the breaker.
Fig. 30 — Cooling Charging Chart,
542J150 Units
Fig. 31 — Cooling Charging Chart,
542J180 Units
—23—
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