Carrier 38YCX instruction manual Defrost Control, Care and Maintenance

If defrost thermostat is in open position, and speedup pins are shorted (with a flat head screwdriver) for 5 sec and released, a short defrost cycle will be observed (actual length is dependent upon the selected Quiet Shift position). When Quiet Shift switch is in ON position, the length of defrost is 1 minute (30 sec compressor off period followed by 30 sec of defrost with com- pressor operation). On return to heating operation, compressor will again turn off for an additional 30 sec and the fan for 40 sec. When the Quiet Shift is in OFF position, only a brief 30 sec cycle will be observed.

If it is desirable to observe a complete defrost in warmer weather, the thermostat must be closed as follows:

1.	Turn off power to outdoor unit.
2.	Disconnect outdoor fan motor lead from OF2 on control board
	(See Fig. 9.) Tape to prevent grounding.
3.	Restart unit in heating mode, allowing frost to accumulate on

	T2 C
	C
	O
O	DFT
R	T1
W

2

Y
C	Y
SPEEDUP	P1
	J1	P3	90 INTERVALTIMER	60 30	30 60	120
	DFT		OFF	QUIET SHIFT		ON
	Speedup				Quiet
	Pins				Shift

OF2

CESO130076–00

Defrost interval

DIP switches

OF1

A99442

outdoor coil.

4. After a few minutes in heating mode, liquid line temperature

should drop below closing point of defrost thermostat (ap-

proximately 30°F).

NOTE: Unit will remain in defrost until defrost thermostat reopens at approximately 80°F coil temperature at liquid line or remainder of defrost cycle time.

5.Turn off power to outdoor and reconnect fan motor lead to OF2 on control board after above forced defrost cycle.

Fig. 9—Defrost Control

CARE AND MAINTENANCE

For continuing high performance and to minimize possible equip- ment failure, periodic maintenance must be performed on this equipment.

Leave User’s Manual with owner. Explain system operation and periodic maintenance requirements outlined in manual. Frequency of maintenance may vary depending upon geographic areas, such as coastal applications.

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