Carrier 38YCX instruction manual LED Status OFF, Flashing

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

1.If equipped with a crankcase heater, energize a minimum of 24 hr before starting unit. To energize heater only, set thermostat OFF and close electrical disconnect to outdoor unit.

2.Fully open liquid and vapor service valves.

3.Unit is shipped with valve stem(s) front seated and caps installed. Replace stem caps after system is opened to refrig- erant flow. Replace caps finger tight and tighten additional 1/6 turn using a backup wrench on valve body flats to prevent distortion of sheet metal.

4.Close electrical disconnects to energize system.

5.Set room thermostat at desired temperature.

6.Set room thermostat to HEAT or COOL and fan to ON or AUTO mode, as desired. Operate unit for 15 minutes. Check system refrigerant charge.

7.Factory charge is shown on unit rating plate. Adjust charge in cooling mode by following procedure shown in charging table. Check charge in heating mode by following procedure shown on heating check chart. Both are located on unit.

•3-phase scroll compressors are rotation sensitive.

•A flashing LED on phase monitor indicates reverse rotation. (See Fig. 8 and Table 2.)

•This will not allow contactor to be energized.

•Disconnect power to unit and interchange 2 field wiring leads on unit contactor.

SEQUENCE OF OPERATION — With power supplied to indoor and outdoor units, transformer is energized. Defrost control board is equipped with 5-minute lockout timer which may be initiated upon any interruption of power.

Cooling

On a call for cooling, the thermostat makes circuits R-O, R-Y, and R-G. Circuit R-O energizes reversing valve, switching it to cooling position. On three phase models with scroll compressors, the units are equipped with a phase monitor to detect if the incoming power is correctly phased for compressor operation. (See Fig. 8 and Table 2.) If phasing is correct, circuit R-Y energizes contactor, starting outdoor fan motor and compressor circuit. R-G energizes indoor unit blower relay, starting indoor blower motor on high speed.

NOTE: If the phasing is incorrect, the contactor will not be energized. To correct the phasing, interchange any two of the three power connections on the field side.

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

NOTE: If indoor unit is equipped with a time-delay relay circuit, the blower runs an additional 90 sec to increase system efficiency.

Heating

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

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Fig. 8—Phase Monitor Control

Table 2—Phase Monitor LED Indicators

LED	STATUS
OFF	No call for compressor
	operation
FLASHING	Reversed phase
ON	Normal

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 supplemental electric heat and providing electrical potential to the second heater sequencer (if used). If outdoor temperature falls below the setting of the outdoor thermostat (field-installed option), 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 contactor and sequencer. All heaters and motors should stop.

→Quiet Shift

Quiet Shift is a field-selectable defrost mode, which will eliminate occasional noise that could be heard at the start of the defrost cycle and restarting of heating cycle. It is selected by placing DIP switch 3 (on defrost board) in ON position.

When Quiet Shift switch is placed in ON position, and a defrost is initiated, the following sequence of operation will occur. Revers- ing valve will energize, compressor will turn off for 30 sec, then turn back on to complete defrost. At the start of heating cycle after conclusion of defrost mode, reversing valve will de-energize, the compressor will turn off for another 30 sec, and the fan will turn off for 40 sec, before starting in the heating mode.

→Defrost

The defrost control is a time/temperature control which includes a field-selectable time period (DIP switch 1 and 2 on the board) between defrost cycles of 30, 60, 90, or 120 minutes (factory set at 90 minutes).

To initiate a forced defrost, two options are available depending on the status of the defrost thermostat.

If defrost thermostat is closed, speedup pins (J1) must be shorted by placing a flat head screwdriver in between for 5 sec and releasing, to observe a complete defrost cycle. When the Quiet Shift switch is selected, compressor will be turned off for two 30 sec intervals during this complete defrost cycle as explained previously. When Quiet Shift switch is in factory default OFF position, a normal and complete defrost cycle will be observed.

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