• 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
o
terminal. This output
signal energizes contactor in heat pump and starts compressor.
There is a 3 to 5 sec delay in output of Y
o
signal.
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
o
, and C. The reading
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 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
o
to energize contactor
in heat pump. There is a 3 to 5 sec delay in output of Y
o
signal.
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
o
, and C. The readings
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.
Table 12—Troubleshooting Voltage Readings and Test Points
Input Voltages
LOCATION
NORMAL READING
PURPOSE
L1 and L2
208/230 vac
Main power supply input to fan coil
L3 and L4
208/230 vac
Power to electric heaters
9-pin connector
7 and 9
208/230 vac
Power to smart control
T1 and T3
208/230 vac
Power to transformer
SEC1 and SEC2
24 vac
Power from transformer secondary
R and C
24 vac
Power from transformer secondary
G and C
24 vac
Call for continuous fan signal from room thermostat
Y and C
24 vac
Call for heat/cool signal from room thermostat
O and C
24 vac
Signal to energize reversing valve from room thermostat (cooling). Also present
during defrost.
W2T and C
24 vac
Call for electric heat from room thermostat
W2D and C
24 vac
Defrost initiation signal from heat pump
Output Voltages
LOCATION
NORMAL READING
PURPOSE
HI and F1
208/230 vac
Power to blower motor (high speed)
LO and F1
208/230 vac
Power to blower motor (low speed)
Y
o
and C
24 vac
Power to energize contactor in heat pump (heat and cool modes)
9-pin connector
1 and 4
24 vdc
Power to energize SEQ 1
NOTE: Sequencers use DC voltage
9-pin connector
2 and 4
24 vdc
Power to energize SEQ 2
9-pin connector
3 and 4
24 vdc
Power to energize SEQ 3
vac—volts AC
vdc—volts DC
49