1. Heating mode
a. When the wall thermostat "calls for heat," the R-W circuit
closes. This closed circuit supplies power to the 24-v safety
circuit containing automatic reset limit switch LS and fuse
link FL.
b. The inducer motor relay coil IDR is energized. Inducer
motor relay contacts in the 115-v circuit close, starting
inducer motor IDM. Simultaneously, another set of con-
tacts in inducer motor relay IDR closes in the 24-v circuit
and locks in until the R and W circuit or safety circuit
opens.
c. As inducer motor IDM comes to speed, pressure switch
PRS actuates and supplies power through manual reset
draft safeguard switch DSS. This process energizes both
solenoid coils in gas valve GV, causing the valve to open
which permits gas flow to the main burners where the gas
is ignited by the pilot.
d. Simultaneously, solid-state time-delay circuit in the blower
control center is energized. Approximately 45 sec after the
R-W circuit is closed, heating fan relay coil HFR is
energized, closing the 115-v contacts of the heating fan
relay HFR and starting blower motor BLWM on heating
speed. EAC terminals energize with 115v when the blower
is operating in either heating or cooling speed.
e. When the thermostat is satisfied, the R-W circuit is broken,
de-energizing both solenoid coils of gas valve GV and the
solid-state time-delay circuit for the fan relay HFR. Gas
flow to the main burners immediately stops. Approximately
120 sec (or 180 sec depending on the blower off time
selected) after main burners are extinguished, heating fan
relay HFR is de-energized and blower motor BLWM stops.
The blower off delay can be permanently changed to 180
sec by cutting resistor. (See Fig. 9.)
f. If the pilot flame is extinguished, the thermocouple no
longer energizes the thermal magnet circuit of gas valve
GV. Gas flow to the pilot and main burners stops until the
pilot is manually relit.
NOTE:
When gas valve GV is energized, R-W circuit is closed.
After a power interruption, the gas valve closes within 7 sec and
the furnace skips the blower on delay and immediately starts the
blower.
2. Cooling mode
When the thermostat "calls for cooling" R, G, and Y circuits
close. Simultaneously, the R-Y circuit starts the outdoor
condensing unit, and the R-G circuit energizes cooling fan
relay coil CFR and heating fan relay coil HFR. The normally
open contacts of heating relay HFR and cooling relay CFR
close, energizing the cooling speed of blower motor BLWM.
Fig. 10—Heating and Cooling Application Wiring Diagram
Table 5—Electrical Data
UNIT SIZE
VOLTS—
HERTZ—
PHASE
OPERATING VOLTAGE RANGE
MAX UNIT AMPS MIN WIRE GAGE
MAX WIRE LENGTH
(FT)‡
MAX FUSE OR
HACR-TYPE CKT
BKR AMPS†
Max*
Min*
071-08
115—60—1
127
104
6.7
14
44
15
071-12
115—60—1
127
104
8.4
14
35
15
091-12
115—60—1
127
104
9.2
14
32
15
091-16
115—60—1
127
104
10.2
14
29
15
110-16
115—60—1
127
104
10.0
14
30
15
110-20
115—60—1
127
104
13.1
12
36
20
135-20
115—60—1
127
104
14.3
12
33
20
* Permissible limits of the voltage range at which the unit will operate satisfactorily (assumes full accessory load).
† Time-delay fuse is recommended.
‡ Length shown is as measured 1 way along wire path between unit and service panel for maximum 2 percent voltage drop.
A78461
115-VOLT FIELD-
SUPPLIED
FUSED
DISCONNECT
AUXILIARY
J-BOX
CONTROL
BOX
24-VOLT
TERMINAL
BLOCK
TWO-WIRE
HEATING-
ONLY
FOUR
WIRE
FIELD-SUPPLIED
FUSED DISCONNECT
CONDENSING
UNIT
TWO
WIRE
FURNACE
R
G
C
W
R
G
Y
GND
GND
FIELD 24-VOLT WIRING
FIELD 115-, 208/230-, 460-VOLT WIRING
FACTORY 24-VOLT WIRING
FACTORY 115-VOLT WIRING
NOTE:
208/230- OR
460-VOLT
THREE
PHASE
208/230-
VOLT
SINGLE
PHASE
WHT
BLK
WHT
BLK
If any of the original wire,
as supplied, must be replaced, use
same type or equivalent wire.
NOTE: Connect Y-terminal as
shown for proper
operation.
W
Y
GND
THERMOSTAT
TERMINALS
8
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