Bryant FA4A - Manual (Page 26)

A U G / 1 4 / 2 0 0 8 / T H U 0 3 : 5 1 UTC TECH PUB F A X N o , 3 1 7 2 4 0 5 6 6 2
2. Blower Off Delay—Smart Heat control uses a 60-scc off
blower delayj as opposed to the standard 90-sec delay.
IIL SMART HEAT OPERATION
A. Cooling
The Smart Heat option controls cooling mode in same manner as
conventional heat pumps are controlled. The fan has a 90-sec delay
off/oji cycle down,
B. Heat Pump Heating
The Smart Heat option docs not control heating in the conventional
method. The PCB energizes compressor 30 sec before indoor fan
is energized. This allows indoor coil to heat up eliminating
cold-blow on start“Up,
The electric heat is staged-on to allow continuous operation of heat
pump and electric,resistance heat below balance point (below point
where heat pump cannot maintain dwelling temperature without
supplemental heat) independent of outdoor thermostats.
Although PCB has provisions for an outdoor thermostat, it is not
needed for staging. On cycle down, indoor fan remains on 60 sec
to recover heat stored in indoor coil,
C- Defrost
The Smart Heat PCB stages the correct amount of supplemental
heat during defrost. If too much heat is added, system stays in
defrost for completion of defrost cycle even though thermostat is
satisfied. On next cycle, 1 less element is energized during next
defrost period.
NOTE: If 24-v power from thermostat is inteiiupted while unit is
in defrost mode, the default cycle will be completed before unit
shuts down.
P. Troubleshooting PrInted-CIrcult Board
(Diagnostic LED)
The PCB of Smart Heat option heater package contains a micro­
processor which controls fan operation, fan speed, outdoor unit,
and heater elements. Bor troubleshooting, a service LED Indicates
condition of PCB, Sec Tabic 8 for LED flash codes,
TABLE 8—LED CODES FOR SMART HEAT PCB
FLASH CONDITION INPUT SIGNALS SYSTEM OPERATION
No Light/Flash —
No Power or
Board Failure
Steady Light
— Board Fallura
Steady Flash —
Stand By Condition
or Fan Only
1 Flash Yonly
Heat Pump Only
Operating
2 Flashes Y and/or W2T
Heat Pump Plus
1 Sequencer
3 Flashes Y and/or W2T
Heat Pump Plus
2 Sequencers
4 Flashes Y and/or W2T
Heat Pump Plus
3 Sequencers
5 Flashes Y. 0 Cool Mode
6 Flashes Y, W2D. and/or W2T Defrost Mode
7 Flashes W2T Emergency Heat Mode
IV. ELECTRICAL OPERATING SEQUENCES AND
TROUBLESHOOTING
NOTE: Refer to Table 9 for proper input and output voltages.
A. Ready-To-Start
In rcady-to-start (standby) mode, LED on board indicates a steady
flash.
In this mode, 24-v power should be available at control's low
voltage terminal strip terminals R and C. If 24v is not present
across R and C, check the followiug:
* Is low-voltage fuse on control board good?
' Are line voltage fuses FUl and FU2 good?
■ Is LED on control on steadily or not on at all? Both of these
indications signal a possible board failure.
‘ Is 2ÜS/230-V power available to control across pins 7 and 9
of 9-pin connector? Is connection to board tight?
B. Continuous Fan
On a call for continuous fan, thermostat provides a 24-v input
signal to G terminal on low-voltage terminal strip. Sensing this
signal, the microprocessor
euergizeiS a relay on control to provide
power to high-speed winding of fan motor, at 1. The fan continues
to run until fan switch on thermostat is turned off.
During continuous fan operation with no call for heating Or
cooling, LED indicates a steady flash, the same indication seen
when system is in standby.
The call for continuous fan operation signal can be checked by
placing voltmeter leads across terminals G and C of control’s
low-voltagc terminal strip. If 24v is not seen across these termi­
nals, check for the following:
’ Is 24v ayailable across R and C? If not, refer to Ready-To-
Start section for items to check if 24v is not available,
■ Is thermostat function switch set for continuous operation?
Confirm fan operation. Voltage to operate fan can be confirmed by
placing.voltmeter leads across terminals FI and Ш on control. The
reading should be 20S/230vi If 20S/230v is not observed, check the
following:
* Is 20S/23ÜV available at pins 7 and 9 of 9-pin connector? Is
connection to board tight?
' Arc line voltage fuses FUl and FU2 good?
If 20&/230V is available across terminals FI 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?
C. Cooling
On a call for cooling, room thennostat provides input signals to
control board at terminals Y and O'.' Thc О 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 terminal. This output
signal energizes contactor in heat pump and starts compressor.
There is a 3 to 5 sec delay in output of signal.
At the same time, control energizes fan coil's fan motor on high
Speed through terminals FI 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 l 0, 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.
D. 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 to energize contactor
in heat pump. There is a 3 to 5 sec delay in output of Y,, signal.
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