Bryant FA4A - Manual (Page 27)

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TABLE 9--TROUBL1ESHOOTING VOLTAGE READINGS AND TEST POINTS
INPUT VOLTAGES
LOCATION NORMAL READING PURPOSE
Li and L2 206/230 vac Main power supply Input to fen coil.
L3 and L4 205/230 vac Power to electric heaters
9-pin connsctpr
7 and 9
208/230 vac Power to smart control
T1 and T3 206/230 vac Power to transformer
SEC1 and SEC2 24 vac Power from transformer secondary
n 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 a n d C 24 vao Call for eiectric 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.Fl 208/230 vac Power to blower ,motor_(low speed)
and C ' 24'vac Power to energize contactor in heat pump (heat and cool modes)
’9-pin connactor
1 and 4
24 vdC
Power to energize SEQ 1
NOTE: Sequencers use DC voltage
9-pln connector
2 arid 4
24 vdc Power to energize SEQ 2
9-pln connector
3 and 4
24 vdc Power to energize SEQ 3
Vac— vetts AC
vdD-^/oltS DC
Thirty Sec after Y is energized, control energizes fan motor. It may There is no hard and fast rule for detennining exactly when stages
run on high or low speedy 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 ejegtric heat.
The call for heat signals can be confirmed by placing voltmeter
leads across dow-‘voltag6 terminals Y, and C; The readings
should be 24v, -If 24v is not available, eheck the following:
■ Is 24v available across R and'C? See Rcady-To-Start section
for items to chedk if 24v is not available.
* Is thermostat function switch set in HEAT position with
theimostat 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. H indoor fan is not mnniog, refer to ,
Continuous Ran 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.
E. Heating (Compressor end Electric Heat)
If heat pump alone cannot satisfy heat requirements of structure,
room thermostat calls for additional heat by way of an input to W2
terminal of control. When this occurs, control begins sequencing
on electric heaters by energizing the first sequencer. Indoor fan
should be running at this time.
If room temperature requirements cannot be met, additional stages
of electric heat are energized through the other 2 sequencers, at 2.
The logic of control determines how much and bow soon these
additional stages are brought on. By observing LED status light,
the number of operating stages of electric heat can be determined.
The control also varies indoor fan speed depending on number of
energized stages of heat. In general, the more stages of electric
heat, the higher the fan speed.
will be energized since microprocessor in the smart control
constantly monitors duration of previous heating cycle, setting of
room thermostat, and number of stages of heat needed in previous
cycle to satisfy room thcmiostat. Rather than try to determine what
should be operating when, service technicians should check LED
status light to see how many stages of electric heat are energJKfid
at a given time and confirm operation of sequencer using a
voltmeter. If a quick check of all stages is desired, set room
thermostat as high as it will go. With a constant signal on W2T
terminal, sequencers energize every 10 minutes until all heaters are
on.
The previous paragraphs described how to' check for low-voltage
inputs to control by placing voltmeter leads across low-voltage
terminal strip and checking for 24v, The call for electric heat can
be confirmed by placing voltmeter leads across W2T and C.
To check for operation of" sequencers, check' directly across
appropriate sequencer coil for 24 volts DC,
NOTE: All sequencer coils are powered by 24 volts DC. This
voltage is generated internally by the smart control.
In this example, sequencer 1 is being checked. The procedure is
the same for all other sequencers. If 24 volts DC is not observed,
check the following;
* Is room thermostat calling for electric heat? This can be
confirmed by checking for 24 volts AC between low-voltage
terminal strip terminals W2T and C-
* Is LED flashing appropriate code for number of sequencers
energized? In this example, 2 flashes should be visible,
indicating 1 sequencer is energized. Indicator tells how many
sequencers are energized, but docs not tell which ones are.
' Is 9-pin connector for heater package tightly secured to
control board?
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