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.
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.
When thermostat is satisfied, its contacts open, de-energizing
contactor and sequencer. All heaters and motors should stop.
Defrost
The defrost control is a time/temperature control which includes a
field-selectable (quick-connects located at board edge) time period
between defrost cycles (30, 50, or 90 minutes), factory set at 90
minutes.
The electronic timer and defrost cycle start only when contactor is
energized and defrost thermostat is closed.
Defrost mode is identical to cooling mode except that outdoor fan
motor stops and second-stage heat is turned on to continue
warming conditioned space.
To initiate defrost, the defrost thermostat must be closed. This can
be accomplished as follows:
1. Turn off power to outdoor unit.
2. Disconnect outdoor fan motor lead from OF2 on control
board. (See Fig. 15.) Tape lead to prevent grounding.
3. Restart unit in heating mode, allowing frost to accumulate on
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).
5. Short between speed-up terminals with a flat-bladed screw-
driver. (See Fig. 15.) This reduces the timing sequence to
1/256th of original time. (See Table 3.)
6. When you hear reversing valve change position, remove
screwdriver immediately; otherwise, control will terminate
normal 10-minute defrost cycle in approximately 2 sec.
NOTE: Length of defrost cycle is dependent on the length of time
it takes to remove screwdriver from test pins after reversing valve
has shifted.
7. Unit will remain in defrost for remainder of defrost cycle time
or until defrost thermostat reopens at approximately 80˚F coil
temperature of liquid line.
8. Turn off power to outdoor unit and reconnect fan motor lead
to OF2 on control board. (See Fig. 15.)
Step 14—Check Charge
Factory charge is shown on unit rating plate. To check charge in
cooling mode, refer to Cooling Only Procedure. To check charge
in heating mode, refer to Heating Check Chart Procedure.
A97413
LEGEND
24-V FACTORY WIRING
24-V FIELD WIRING
FIELD SPLICE CONNECTION
OUTDOOR THERMOSTAT
EMERGENCY HEAT RELAY
SUPPLEMENTAL HEAT RELAY
SHR
EHR
ODT
WIRING DIAGRAM NOTES:
1. CARRIER THERMOSTAT WIRING DIAGRAMS ARE ONLY ACCURATE FOR MODEL NUMBERS 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 24-V 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 INSTRUCTIONS.
6. UNDERLINED LETTER ON DUAL TERMINAL INDICATES ITS USAGE.
FOR EXAMPLE: O/W2 MEANS O
O/W2 MEANS W2
7. OUTDOOR TEMPERATURE SENSOR MUST BE ATTACHED 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.
11
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