Cooling Sequence Of Operation - Bryant Legacy 574D----A Installation Instructions Manual

speed when the DH control lead is not energized, or IFB "HIGH"
speed when the DH lead is energized (see Fig. 17).
GAS
HEAT
QC6
K2
RL3 C8
RI0
C9
C4
OILL C2 D6 D4
A7
R9
D5 D3
C7
R3 R5 R6
R2
QCB
JW7
Y
Y
SSTZ-8
Fig. 17 - - Interface Fan Board (IFB)
HIGH LOW COM
QC7 QC4 QC3
K1
DCR QCR
C
R1L Q1
D2
QC1
JM6
Q3
RI2
RI DL
JM5
G1
G2
AB A15
F1
C0
U1
R4 RL4
C3
JW3
P2
JW2
JW4
R U C 24VAC
JW1
P1
W2 Y2/ Y1/
G C R
DH Y
A09058
Table 6 – Color Coding for Indoor Fan Motor Leads
Black = High Speed
Orange = Med--- High Speed
Red = Med Speed
Pink = Med--- Low Speed
Blue = Low Speed

Cooling Sequence of Operation

With the room thermostat SYSTEM switch in the COOL position
and the FAN switch in the AUTO position, the cooling sequence
of operation is as follows:
1. When the room temperature rises to a point that is slightly
above the cooling control setting of the thermostat, the
thermostat completes the circuit between thermostat
terminal R to terminals Y and G.
2. The normally open contacts of energized contactor (C) close
and complete the circuit through compressor motor
(COMP) to condenser (outdoor) fan motor (OFM). Both
motors start instantly.
3. The set of normally open contacts on the interface fan board
(IFB) are closed which energizes a circuit to the indoor fan
motor (IFM).
NOTE: Once the compressor has started and then stopped, it
should not be started again until 5 minutes have elapsed. The
cooling cycle remains on until the room temperature drops to a
point that is slightly below the cooling control setting of the room
thermostat. At this point, the thermostat breaks the circuit between
thermostat terminal R to terminals Y and G. These open circuits
deenergize contactor coil C. The condenser and compressor motors
stop. After a 90- -sec. delay, the blower motor stops. The unit is in a
standby condition, waiting for the next call for cooling from the
room thermostat.
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