User`s manual

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33
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V. REFRIGERANT CHARGE
A. Checking and Adjustment Refrigerant Charge
The refrigerant system is fully charged with R-22 refriger-
ant, tested, and factory-sealed. Unit must operate in Cooling
mode a minimum of 10 minutes before checking charge.
NOTE: Adjustment of the refrigerant charge is not required
unless the unit is suspected of not having the proper R-22
charge.
A superheat charging chart is attached to the outside of the
service access panel. The chart includes the required suction
line temperature at given suction line pressures and outdoor
ambient temperatures.
An accurate superheat, thermocouple- or thermistor-type
thermometer and a gage manifold are required when using
the superheat charging method for evaluating the unit
charge. Do not use mercury or small dial-type thermosmeters
because they are not adequate for this type of measurement.
Proceed as follows:
1. Remove caps from low- and high-pressure service
fittings.
2. Using hoses with valve core depressors, attach
low- and high-pressure gage hoses to low- and high-
pressure service fittings, respectively.
3. Start unit in Cooling mode and let unit run 10 min-
utes until system pressures stabilize.
4. Measure and record the following:
a. Outdoor ambient-air temperature (F db).
b. Evaporator inlet-air temperature (F db).
c. Suction-tube temperature (F) at low-side service
fitting.
d. Suction (low-side) pressure (psig).
5. Using “Cooling Charging Charts” compare outdoor-
air temperature (F db) with the suction line pressure
(psig) to determine desired system operating suction
line temperature. See Fig. 54-57.
6. Compare actual suction-tube temperature with
desired suction-tube temperature. Using a tolerance
of ±3
°
F, add refrigerant if actual temperature is
more than 3
°
F higher than proper suction-tube tem-
perature, or remove refrigerant if actual temperature
is more than 3
°
F lower than required suction-tube
temperature.
B. To Use Cooling Charging Charts
This method is to be used in Cooling mode only.
Take the outdoor ambient temperature and read the suction
pressure gage. Refer to appropriate chart to determine what
suction temperature should be. If suction temperature is
high, add refrigerant. If suction temperature is low, carefully
reclaim some of the charge. Recheck the suction pressure as
charge is adjusted.
EXAMPLE: (Fig. 57, Circuit No. 1)
Outdoor Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 F
Suction Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 psig
Suction Temperature should be . . . . . . . . . . . . . . . . . . . 58 F
(Suction Temperature may vary ± 5 F.)
C. Refrigerant Leaks
Proceed as follows to repair a refrigerant leak and to charge
the unit:
1. Locate leak and ensure that refrigerant system pres-
sure has been relieved.
2. Repair leak following accepted practices.
NOTE: Install a filter drier in the liquid line whenever the
system has been opened for repair. Install filter drier where
strainer assembly is located.
3. Add a small charge of R-22 refrigerant vapor to sys-
tem and leak-test unit.
4. Evacuate refrigerant system to 500 microns if addi-
tional leaks are not found.
5. Charge unit with R-22 refrigerant, using a volumetric-
charging cylinder or accurate scale. Refer to unit rating
plate for required charge. Be sure to add extra refriger-
ant to compensate for internal volume of filter drier.
CAUTION: When evaluating the refrigerant
charge, an indicated adjustment to the specified fac-
tory charge must always be very minimal. If a substan-
tial adjustment is indicated, an abnormal condition
exists somewhere in the cooling system, such as insuf-
ficient airflow across either coil or both coils.
Fig. 51 — Propping Up Top Panel
Fig. 52 — Separating Coil Sections
Fig. 53 — Condenser Fan Adjustment
UNIT
VOLTAGE
FAN HEIGHT
‘‘A’’ (in.)
208/230 v
2.75
460 and 575 v
3.50