Sequence of Operation

WIRING DIAGRAM NOTES:

1. CARRIER THERMOSTAT-WIRING DIAGRAMS ARE
ONLY ACCURATE FOR MODEL NUMBERS BEGINNING
WITH TSTAT_ _ _ _ _ _ _.
2. WIRING MUST CONFORM TO NEC OR LOCAL CODES.
3. SOME UNITS ARE EQUIPPED WITH PRESSURE
SWITCH(ES), TEMPERATURE SWITCH, OR 5–MINUTE
COMPRESSOR-CYCLE PROTECTION. CONNECT				24V
FIELD WIRING TO FACTORY-PROVIDED STRIPPED
LEADS.
4. THERMOSTATS ARE FACTORY CONFIGURED WITH
5-MINUTE COMPRESSOR-CYCLE PROTECTION				AND
4-CYCLES-PER-HR	LIMIT.	SEE	THERMOSTAT-
INSTALLATION INSTRUCTIONS FOR DETAILS.
5. TO STAGE ELECTRIC-RESISTANCE HEAT, CONSULT
OUTDOOR THERMOSTAT-INSTALLATION INSTRUC-
TIONS.
6. UNDERLINED LETTER ON DUAL TERMINAL INDI-
CATES ITS USAGE.

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

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.

FOR EXAMPLE: O/W2 MEANS O; O/W2MEANS W2

7. OUTDOOR-TEMPERATURE SENSOR MUST BE AT-

TACHED IN ALL DUAL-FUEL INSTALLATIONS. JUMPER

WIRE BETWEEN O/W2 AND L THERMOSTAT TERMINALS

MUST BE PRESENT.

8. Y1 AND O CONNECTIONS TO 2–STAGE FURNACES

MAY NOT EXIST OR MAY ONLY BE A WIRE RATHER

THAN A SCREW TERMINAL.

NOTE: Defrost-control board is equipped with 5-minute lockout timer that may be initiated upon any interruption of power.

With power supplied to indoor and outdoor units, transformer is energized.

Cooling

On a call for cooling, thermostat makes circuits R-O, R-Y, and

	T2 C
	C
	O
O	DFT
R	T1
W

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

OF2

OF1

CESO130076–00

Defrost interval

DIP switches

A91444

R-G. Circuit R-O energizes reversing valve, switching it to cooling position. On 3-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. If phasing is correct, circuit R-Y energizes contactor, starting outdoor-fan motor and compressor circuit. R-G energizes indoor unit-blower relay, start- ing indoor-blower motor on high speed.

NOTE: If the phasing is incorrect, the contactor will not be energized. To correct the phasing, interchange any 2 of the 3 power connections on the field side.

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

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

→	Fig. 8—Defrost Control

→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.

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.

WIRING DIAGRAM NOTES:

SEQUENCE OF OPERATION

Fig. 8—Defrost Control