Bryant 764A Iv. Electrical Controls And Wiring, V. Indoor Airflow, Vi. Metering Device Servicing

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 ®eld 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 air¯ow 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 ®lter is clean. When necessary, refer to Indoor Air¯ow and Air¯ow Adjustments section on page 13 to check the system air¯ow.

VI. METERING DEVICE SERVICING

Refrigerant metering devices are ®xed ori®ces 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 ¯owing 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 ®tting 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 ®rms.

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 speci®ed 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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