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IV. ELECTRICAL CONTROLS AND WIRING
Inspect and check the electrical controls and wiring an-
nually. Be sure to turn off all electrical power to the unit.
Remove the control, evaporator fan, and compressor compart-
ment access panels to locate all the electrical controls and
wiring. Check all electrical connections for tightness. Tighten
all screw connections. If any smoky or burned connections are
noticed, disassemble the connection and clean all the parts.
Then restrip the wire end, and reassemble the connection prop-
erly and securely.
After inspecting the electrical controls and wiring, replace all
the panels. Start the unit, and observe at least one complete
heating cycle (if accessory electric heaters are field installed
in unit) and one complete cooling cycle to ensure proper
operation. If discrepancies are observed in either or both
operating cycles, or if a suspected malfunction has occurred,
check each electrical component with the proper electrical
instrumentation. Refer to unit wiring label when performing
these checkouts.
NOTE: Refer to the Cooling Sequence of Operation on
page 13 as an aid in determining proper control operation.
V. INDOOR AIRFLOW
The airflow does not require checking unless improper per-
formance is suspected. If a problem exists, be sure that all
supply- and return-air grilles are open and free from obstruc-
tions, and that the air filter is clean. When necessary, refer
to Indoor Airflow and Airflow Adjustments section on
page 13 to check the system airflow.
VI. METERING DEVICE SERVICING
Refrigerant metering devices are fixed orifices and are lo-
cated in the inlet header to the evaporator coil.
VII. LIQUID LINE STRAINER
Strainer is made of wire mesh and is located in the liquid
line on inlet side. Remove strainer by cutting it from the liq-
uid line. Braze a new strainer into liquid line with nitrogen
gas flowing through the refrigerant system.
VIII. REFRIGERANT CHARGE
WARNING: Avoid contact with hot gas discharge line
to prevent a burn when working on compressor.
CAUTION: To prevent personal injury, wear safety
glasses and gloves when handling refrigerant.
Do not overcharge system. An overcharge can cause com-
pressor damage.
Unit refrigerant system is factory charged. When recharging
is necessary, weigh in total charge indicated on unit name-
plate. Remove and recover any refrigerant remaining in
system before recharging. If system has lost complete charge,
evacuate system to 500 microns (29.90-in. Hg vacuum) be-
fore recharging. Schrader fitting connections are provided on
unit suction and discharge lines for evacuation and charg-
ing. Dial-a-Charge charging cylinder is an accurate device used
to charge systems by weight; these cylinders are available at
refrigeration supply firms.
A. Adjusting Refrigerant Charge
Amount of refrigerant charge is listed on unit nameplate (also
refer to Table 1). Refer to Carrier Refrigerant Service Tech-
niques Manual, Refrigerants section.
Unit panels must be in place when unit is operating during
charging procedure.
No Charge
Use standard evacuating techniques. After evacuating
system, weigh in the specified amount of refrigerant (refer to
Table 1).
Low Charge Cooling
Use Cooling Charging Charts, Fig. 19-24. Vary refrigerant un-
til the conditions of the appropriate chart are met. Note that
charging charts are different from the type normally used.
Charts are based on charging the units to the correct super-
heat for the various operating conditions. Accurate pressure
gage and temperature sensing device are required.
To measure suction pressure, perform the following:
1. Connect the pressure gage to the service port on the suc-
tion line.
2. Mount the temperature sensing device on the suction
line and insulate it so that outdoor ambient tempera-
ture does not affect the reading. Indoor-air cfm must be
within the normal operating range of the unit.
To Use Cooling Charging Charts
1. Take the outdoor ambient temperature and read the suc-
tion pressure gage.
2. Refer to appropriate chart to determine what the suc-
tion temperature should be.
3. If suction temperature is high, add refrigerant. If suc-
tion temperature is low, carefully recover some of the
charge.
4. Recheck the suction pressure as charge is adjusted.
EXAMPLE: (Fig. 19)
Outdoor Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 F
Suction Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 psig
Suction Temperature should be . . . . . . . . . . . . . . . . . . . 70 F
(Suction Temperature may vary ± 5° F.)
If Chargemaster charging device is used, temperature and
pressure readings must be accomplished using the charging
chart.
IX. REPLACEMENT PARTS
A complete list of replacement parts may be obtained from
your distributor upon request.
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