Carrier FA4ANF Service Manual page 49

Table 12—Troubleshooting Voltage Readings and Test Points
LOCATION NORMAL READING
L1 and L2
L3 and L4
9-pin connector
7 and 9
T1 and T3
SEC1 and SEC2
R and C
G and C
Y and C
O and C
W2T and C
W2D and C
LOCATION
HI and F1
LO and F1
Y and C
o
9-pin connector
1 and 4
9-pin connector
2 and 4
9-pin connector
3 and 4
vac—volts AC
vdc—volts DC
• Is thermostat fan switch set for continuous operation?
Confirm fan operation. Voltage to operate fan can be confirmed by
placing voltmeter leads across terminals F1 and HI on control. The
reading should be 208/230v. If 208/230v is not observed, check the
following:
• Is 208/230v available at pins 7 and 9 of 9-pin connector? Is
connection to board tight?
• Are line voltage fuses FU1 and FU2 good?
If 208/230v is available across terminals F1 and HI and fan does
not operate, check the following:
• Is fan motor capacitor good?
• Is blower wheel jammed or loose? Are there any other
mechanical problems preventing fan operation?
COOLING
On a call for cooling, room thermostat provides input signals to
control board at terminals Y and O. The O signal is also available
to heat pump to energize reversing valve.
When it receives both these signals, the microprocessor responds
by providing a 24-v output signal at the Y
signal energizes contactor in heat pump and starts compressor.
There is a 3 to 5 sec delay in output of Y
At the same time, control energizes fan coil's fan motor on high
speed through terminals F1 and HI. The LED indicator on control
signals 5 flashes, indicating cooling operation.
The call for cooling signals can be confirmed by placing voltmeter
leads across low-voltage terminals Y, O, Y
should be 24v. If 24v is not available, check the following:
• Is 24v available across R and C? See Ready-To-Start section
for items to check if 24v is not available.
Input Voltages
208/230 vac Main power supply input to fan coil
208/230 vac Power to electric heaters
208/230 vac Power to smart control
208/230 vac Power to transformer
24 vac Power from transformer secondary
24 vac Power from transformer secondary
24 vac Call for continuous fan signal from room thermostat
24 vac Call for heat/cool signal from room thermostat
Signal to energize reversing valve from room thermostat (cooling). Also present
24 vac
during defrost.
24 vac Call for electric heat from room thermostat
24 vac Defrost initiation signal from heat pump
Output Voltages
NORMAL READING
208/230 vac
208/230 vac
24 vac
24 vdc
24 vdc
24 vdc
terminal. This output
o
signal.
o
, and C. The reading
o
PURPOSE
PURPOSE
Power to blower motor (high speed)
Power to blower motor (low speed)
Power to energize contactor in heat pump (heat and cool modes)
Power to energize SEQ 1
NOTE: Sequencers use DC voltage
Power to energize SEQ 2
Power to energize SEQ 3
• Is thermostat function switch set in COOL position with
thermostat calling for cooling?
Assuming heat pump has power and is adequately charged, it
should be running at this time in cooling mode. Indoor fan should
also be running at this time. If indoor fan is not running, refer to
Continuous Fan section for items to check.
HEATING (COMPRESSOR ONLY)
On a call for heat, room thermostat provides an input signal to
control board at terminal Y. This signal causes the microprocessor
to provide a 24-v output signal at terminal Y
in heat pump. There is a 3 to 5 sec delay in output of Y
Thirty sec after Y is energized, control energizes fan motor. It may
run on high or low speed, depending on its operation in previous
cycle.
Compressor operation in current cycle is monitored by the smart
control to determine whether a fan speed change is required for
enhanced indoor comfort. The LED indicator on control signals 1
flash, indicating compressor operation only with no electric heat.
The call for heat signals can be confirmed by placing voltmeter
leads across low-voltage terminals Y, Y
should be 24v. If 24v is not available, check the following:
• Is 24v available across R and C? See Ready-To-Start section
for items to check if 24v is not available.
• Is thermostat function switch set in HEAT position with
thermostat calling for heat?
Assuming heat pump has power and is adequately charged, it
should be running at this time in heating mode. Indoor fan should
also be running at this time. If indoor fan is not running, refer to
Continuous Fan section for items to check. When room thermostat
is satisfied, indoor fan continues to run an additional 60 sec to
recover heat remaining in indoor coil.
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to energize contactor
o
signal.
o
, and C. The readings
o