Troubleshooting Pcb - Bryant SM03-4 Service Manual

6. W2 is used to turn on the first stage of electric heat which
is interlocked with the fan through the normally closed fan
relay. Unless the tabs are broken off, all stages of electric
heat will turn on when W2 receives a signal from the
thermostat.
7. W3 is used to turn on the second stage of electric heat. Note
the W2 and W3 tab must be broken off for individual
staging to take place. Energizing W3 will always turn on the
first stage through the diodes even if the tabs are broken off.
8. E is used to turn on the third stage of electric heat. Note that
the W3 and E tab must be broken for this individual staging.
Energizing E will always turn on the first stage through the
diodes even if the tab is broken off.
9. L is used as a junction to wire a diagnostic light (LED) on
selected thermostats.
B. Transformer
The proper wiring of the transformer on the HK61GA001 board is
illustrated in Fig. 8. Note that T1, T2, and T3 are wired to the
primary or high side of the transformer. The blue wire is connected
to T3 for 208-v applications. The red wire is connected to T3 for
230-v applications. Units are factory wired at 230v. The T2
terminal is a dummy.
C. Indoor Fan
1. Wiring--The fan connects to F1, F2, F3, and F4 as shown in
Fig. 8. Note that F2 and F3 are dummy terminals. The
desired fan speed is connected to F4 and the common is
connected to F1. Units are factory wired at medium speed.
2. Functional Control
a. Thermostat and Relay Control--When the thermostat
calls for the fan in cooling, heat pump, electric heat, or
fan-only mode, a 24-v dc signal is sent to the relay. This
causes the relay to close its normally open contacts, thus
turning on the fan. When the thermostat no longer calls
for the fan, the signal sent to the relay is turned off and
the relay opens causing the fan to turn off. The
HK61GA003 board contains a 90-sec fan-off delay when
Y is de-energized.
b. Sequencer Interlock--The fan will also turn on whenever
there is any call for electric heat, even if the fan relay is
not energized. This happens because the fan is inter-
locked with the first stage of electric heat through the
normally closed contact of the fan relay.
D. Electric Heat
When the thermostat calls for electric heat, a 24-v signal is sent to
the PCB through W2, causing the first stage to turn on. W3 and E
also receive the signal if the tabs are not broken off the PCB. The
signal sent to W2 causes the first stage to turn on. If the tabs are
broken off the PCB, the sequencers can be controlled individually
to stage the electric heat. The sequence control is described in the
following section:
1. W2--When the thermostat sends a signal to W2, a 24-v dc
signal is applied across sequencer number 1, causing it to
close. When sequencer number 1 closes, the first stage of
electric heat energizes after a short delay. In straight electric
heat, the fan is also energized through the normally closed
contacts of the fan relay. In cooling, heat pump, or manual
fan mode, the fan will already be running since the fan relay
would have been energized. When the thermostat stops
calling for electric heat, the 24-v dc signal to sequencer
number 1 turns off and the sequencer opens after a delay of
60 to 90 sec. When the sequencer opens, the first stage of
heat turns off along with the fan, providing that the
thermostat is not calling for the fan. Note that the electric
heat cannot be turned on without the fan being turned on at
the same time. This is a fan interlock system.
2. W3--When a signal is sent to W3, 2 control signals are sent
out to the sequencers; a 24-v dc signal to sequencer number
1 through the diode interlock, and a 24-v ac signal to
sequencer number 2. The 24-v ac signal applied to sequence
number 2 causes the sequencer to close, with the second
stage of electric heat turning on after a short delay.
The 24-v dc signal applied to sequencer number 1 causes the first
stage of electric heat to turn on in the same manner as described in
W2 above. Note that W3 is interlocked with the fan, since
sequencer number 1 is turned on whenever W3 has a signal sent to
it. Timing is such that sequencer number 1 will turn on before
sequencer number 2. When the signal to W3 is turned off,
sequencer number 2 opens after a short delay. If W2 is also
satisfied, the first stage of electric heat and the fan will also turn
off, providing the thermostat is not calling for the fan to be on.
E--When the thermostat sends a signal to E 2 signals are sent out
to the sequencers. A 24-v ac signal is sent to sequencer number 3
and a 24-v dc signal is sent to sequencer number 1. The 24-v ac
signal applied to sequencer number 3 turns on the third stage of
electric heat. The 24-v dc signal applied to sequencer 1 turns on the
first stage of electric heat and the fan in the same manner as W3.
Note that E is also interlocked with the fan.
When the thermostat stops calling for electric heat, the signals to
sequencers 1 and 3 are turned off and the sequencers open. This
causes the electric heat to turn off with the fan if the thermostat is
not calling for the fan.
E. Accessories
1. EAC1 and EAC2 for Electronic Air Cleaners
a. There are 240-v electronic air cleaner contacts provided
at EAC1 and EAC2. The electronic air cleaner is
connected in parallel with the fan so that it is on
whenever the fan is on. A 120-v installation is similar in
function but connected between EAC2 and neutral of
230-v: 120-v transformer connected to EAC1 and EAC2.
Refer to electronic air cleaner literature for further
information.
2. AUX1 and AUX2 for 2-Speed Fan Relay Kit
a. Use to control fan speed operation, high speed for
cooling, heat pump, and fan-only modes. Low speed is
used for electric heat. Fig. 9 shows proper connection for
24-v dc 2-speed fan relay kit. Note that kit's relay coil is
in parallel with fan relay coil on PCB connected to
AUX1 and AUX2. Make sure the normally closed
contact is connected to the lower speed.
b. The latent capacity control kit is used to control fan
speed operation when the relative humidity is above a set
point on humidistat. Humidistat opens and 2-speed fan
relay remains in normally closed position with fan motor
running at a lower speed for maximum humidity control.
Fig. 10 shows proper connection for latent capacity
control kit. Note that it is connected in the same manner
as 2-speed fan relay kit but with relay connected to
humidistat (orange wires).
c. Time delay-off relay kit is used to increase the efficiency
of the system by delaying the fan from turning off after
the thermostat is satisfied on the HK61GA001 board.
The HK61GA003 board has this feature as standard. The
proper wiring and mounting of the time delay-off relay
kit is shown in Fig. 11.
d. Latent capacity control and time delay-off connections
are shown in Fig. 12, for the HK61GA001 board only.
III. TROUBLESHOOTING
BOARD
Use Fig. 13 wiring schematic as a guide in troubleshooting the
PCB unless otherwise noted.
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THE PRINTED-CIRCUIT