Unit Functions - Carrier FA4ANF Service Manual

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
terminal provides output from control board to energize
o
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.).
CEPL130121-01
MOV1
SEC2
FS1
SEC1
R1
R30
R3
D5
R23
C6 Z5
C5 C2
1
R8
C13
R21
R9
C3 JW7
R20
C12
C10
R16
R13
R2
R19
R10
C9
R5
JW6 C8
R40
R18
R11
R41
C7
R15
1
R4
R27
XFORM
T1
DUMMY
T2
240 VAC
F1
T3
COMMON
FAN
HI
240
VAC
DUMMY
LO
F2
Fig. 39—Smart Heat Printed-Circuit Board (PCB)
ST1
LOW VOLTAGE
TERMINAL
R
BOARD
C
R7
R6
Y
Z4
G
R12
C11
O
R17
W2D
Z3
W 2T
JW1
JW1
(CUT WHEN
Z2
W 3
OUTDOOR
THERMOSTAT
JW8
Y o
IS USED)
AUX–
JW2
AUX+
(HIGH FAN
ONLY WHEN
K2
CUT)
RECEPTACLE
K3
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.
47
A94127