Carrier 38YRA instruction manual ÐChecking Charge, Care and Maintenance

5.Set room thermostat at HEAT or COOL and fan switch at ON or AUTO, as desired. Operate unit for 15 minutes. Check system refrigerant charge. (See Step 10.)

SEQUENCE OF OPERATION Ð With power supplied to indoor and outdoor units, transformer is energized.

Cooling

On a call for cooling, the thermostat makes circuits R-O, R-Y, and R-G. Circuit R-O energizes the reversing valve, switching it to cooling position. Circuit R-Y energizes the contactor, starting outdoor fan motor and compressor circuit. R-G energizes the indoor unit blower relay, starting the indoor blower motor on high speed.

When the thermostat is satisfied, its contacts open, de-energizing the contactor and blower relay. Compressor and motors should stop.

Heating

On a call for heating, the thermostat makes circuits R-Y and R-G. Circuit R-Y energizes contactor, starting outdoor fan motor and compressor. Circuit R-G energizes the indoor blower relay, start- ing the blower motor on high speed.

Should the temperature continue to fall, R-W2 is made through the second-stage room thermostat bulb. Circuit R-W2 energizes a sequencer, bringing on the first bank of supplemental electric heat and providing electrical potential to the second heater sequencer (if used). If the outdoor temperature falls below the setting of the outdoor thermostat (field-installed option), the contacts close to complete the circuit and bring on the second bank of supplemental electric heat.

When the thermostat is satisfied, its contacts open, de-energizing the contactor and sequencer. All heaters and motors should stop.

Defrost

The defrost control is a time/temperature control which includes a field-selectable (quick connect pins located at edge of circuit board) time period between defrost cycles (30, 50, and 90 minutes), factory set at 90 minutes.

The electronic timer and the defrost cycle will start only when the contactor is energized and the defrost thermostat is closed.

The defrost mode is identical to the cooling mode except the outdoor fan motor stops and a second-stage heat is turned on to continue warming the conditioned space.

Step 10ÐChecking Charge

Do not vent refrigerant to atmosphere. Recover during system repair or final unit disposal.

Factory charge is shown on unit rating plate. (See Fig. 2.)

Service valve gage ports are not equipped with Schrader valves. To prevent personal injury, make sure valves are fully back seated before removing gage port caps. Wear safety glasses and gloves when handling refrigerant.

Compressor damage may occur if system is overcharged.

Adjust charge in cooling mode by following procedure shown on the subcooling charging tables located on unit information plate. Check charge in heating mode by following procedure shown on heating check chart located on unit information plate.

CARE AND MAINTENANCE

For continuing high performance and to minimize possible equip- ment failure, it is essential that periodic maintenance be performed on this equipment. Consult your servicing contractor or User's Manual for the proper frequency of maintenance. Frequency of maintenance may vary depending upon geographic areas, such as coastal applications.

Step 1ÐLeave User's Manual with Homeowner

Explain system operation and maintenance procedures outlined in User's Manual.

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