d. G terminal provides input signal from thermostat signaling
continuous fan operation.
e. O terminal provides input and junction terminal for revers-
ing valve signal.
f. W2D terminal provides input from outdoor unit (heat
pump) signaling control board that heat pump is in defrost.
g. W2T terminal provides input from thermostat signaling for
supplemental or emergency heat.
h. W3 terminal provides input from outdoor thermostat. W3
and W2T are factory connected by JW1. This input is used
only if an outdoor thermostat is required by local codes.
i. Y
o
terminal provides output from control board to energize
outdoor unit (heat pump) contactor.
2. Jumper wires (JW1 and JW2). (See Fig. 39.)
a. JW1 connects W2T to W3 to limit staging of electric heat
with use of an outdoor thermostat. See Table 10 for staging.
Smart Heat PCB controls staging to the extent that this
feature is unnecessary unless required by local codes or
regulations.
b. Cutting JW2 sets Smart Heat PCB in efficiency mode.
With JW2 cut, there is no loss of performance due to
reduced indoor blower speed when heat pump is operating
near balance point. This jumper may need to be cut if
selected cooling fan speed is the same as required mini-
mum motor LO speed tap selection. With JW2 cut, fan
terminal LO becomes a dummy terminal.
3. A fuse is used to protect low-voltage transformer and PCB.
4. AUX+ and AUX- are connections for air conditioning acces-
sories (EAC, humidifier, etc.).
5. F1, F2, HI, and LO are connections for indoor fan.
6. The 9-pin receptacle connects heater package wiring harness.
7. SEC1 and SEC2 are used to connect secondary side of
transformer to PCB. SEC1 is internally connected to equip-
ment ground.
Step 2—Unit Functions
TRANSFORMER
NOTE:
Terminals T1, T2 (if used), and T3 are wired to primary
or high side of transformer. The 208-v terminal (or blue wire if
transformer has primary leads) is used on T3 for 208-v applica-
tions. The 230-v terminal (or red wire) is used on T3 for 230-v
applications. T2 is a dummy terminal.
ELECTRIC HEAT
NOTE:
When troubleshooting elements, position thermostat to
emergency heat. Wait approximately 12 minutes after all thermo-
stat delays for all elements to come on.
1. When thermostat calls for supplementary heat, a 24-v signal is
sent to PCB through W2T. The PCB energizes first stage of
electric heat.
2. The first 2 stages come on if W2T and Y are energized at the
same time. After each 10 minutes W2T is energized, another
stage of electric heat is energized.
3. As W2T is de-energized, electric heat stages down in 8 minute
steps with the exception of first step. The first step will be on
only half as long as it was prior to W2T de-energizing.
4. When W2T is energized by itself, JW1 is cut, and an outdoor
thermostat is used and is open, staging is limited as in Table
10.
Fig. 39—Smart Heat Printed-Circuit Board (PCB)
A94127
ST1
®
®
HSCI
COMMON
DUMMY
DUMMY
240 VAC
240
VAC
JW4
JW2
JW3
JW5
JW6
JW8
JW1
R15
R27
R4
R41
1
R40
R19
R10
C9
C8
R18
R11
C7
K2
K3
LO
HI
T3
T2
T1
F1
XFORM
AUX+
AUX–
F2
FAN
R13
C10
C12
C13
FS1
R20
R9
R8
R7
R6
Z4
C5
1
MOV1
C2
C3
C6
R23
R1
R30
D5
R
C
Y
G
O
W2D
W 3
Y o
W 2T
R3
Z5
R21
JW7
R2
Z3
Z2
R16
R12
C11
R17
R5
R29
R26
R14
K1
D1
C
BE
C
BE
C
BE
D4
D2
U2
U1
LED1
D3
Q1
P1
LR40061
CLIP JUMPER FOR
HIGH SPEED FAN ONLY
Q2
1
2
3
4
5
6
7
8
9
Q3
R38
R22
R28
R25
R24
CESS430121-01A
R36
R37
C15
Z1
C14
R39
C4
CES0130025 –
SEC1
SEC2
CEPL130121-01
JW1
JW2
RECEPTACLE
LOW VOLTAGE
TERMINAL
BOARD
(CUT WHEN
OUTDOOR
THERMOSTAT
IS USED)
(HIGH FAN
ONLY WHEN
CUT)
47
