American Standard S9B1 Installer'S Manual Download

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18-CE12D1-1D-EN

Sequence of Operation

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e:: The seven segment LED readout is based solely

on thermostat input.. During a simultaneous call
for W1 and W2, the seven-segment will read

Xt2

although the IFC will process the call for 1

stage

heat first.

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1. R – W contacts close on the thermostat sending

24VAC to the W1 low voltage terminal of the IFC.
Technician should read 24VAC from W to B/C. The
seven-segment LED will read:

Xt1

= 1

Stage gas heat (S9X2)

= Gas Heat (S9X1, S9B1)

2. The IFC performs a self-check routine and then

confirms that the:

a. Condensate pressure switch and Inducer limit

switch are closed by sending 24VAC out the
HLO terminal and monitoring the ILI input.

b. Flame roll-out switches (FRS) 1 & 2, main

thermal limit (TCO), and any reverse air flow
(RAF) switches are closed by sending 24VAC out
the HLO terminal and monitoring the HLI input.

c. Pressure switch 1 (PS1) and pressure switch 2

(PS2 – S9X2 only) are open by sending 24VAC
out the HLO terminal, through the limit
switches, and monitoring the PS1 and PS2
inputs.

otte

e:: If a thermal limit is open, 24VAC will not be

present at the pressure switch.

3. After steps a, b, and c are confirmed, the inducer

relay is closed energizing the inducer motor.

4. As the inducer ramps up, PS1 will close.
5. When PS1 closes, the ignitor relay on the IFC will

close. The ignitor is energized. The ignitor warm up
is approximately 17 seconds.

6. After the ignitor warm up, the gas valve relay is

closed on the IFC, which energizes the gas valve
solenoid to allow ignition.

7. The first burner will ignite, and flame will crossover

to the remaining burners, establishing current to
the flame sensor. Proof of flame must be
established within 4 seconds.

otte

e:: There are two flame sense pads located on

the IFC marked as “FP”. To measure the
flame current, use a VOM set to DC volts.
1VDC = 1 micro-amp. Flame current will vary
depending on the type of meter used. Typical
flame current ranges from 0.75 – 3.0 micro-
amps (0.75 – 3 VDC).

8. Once flame sense has been established, a timer on

the IFC starts, and the indoor blower will energize at
1

stage speed after the blower “Heat On Delay”

has completed.. The seven-segment LED for
example will alternately read:

= Gas heating = S9X1 / S9B1

Xt1

= Gas heating, Stage 1 = S9X2

TP2

= Speed Tap 2

9. When the temperature raises enough to satisfy the

thermostat setting, contacts R-W will open.

10. The gas valve relay will open, closing the gas valve.

The inducer will continue to run for approximately 5
seconds to remove any combustion by-products
from inside the furnace.

11. The indoor blower continues to run to remove heat

from the heat exchangers. The blower off time is
field adjustable through the IFC menu setup option.
The seven segment LED will read

IDL

= Idle, no

thermostat demand.

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1. See sequence of operation for 1

stage gas heating

operation above (steps 1-8)

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e:: 2

stage heating cannot operate without 1

stage operating.

2. R-W2 contacts close on the thermostat sending

24VAC to the W2 low voltage terminal of the IFC.
Technician should read 24VAC from W2 to B/C. The
seven-segment LED will read

3. The IFC checks to ensure that PS2 is open, and then

energizes the 2

stage inducer relay. The inducer

is energized on high speed, and the second stage
gas valve relay on the IFC closes, energizing second
stage gas valve. The indoor blower motor will ramp
up to the 2

stage gas heating speed. The seven-

segment LED for example will alternately read:

= Gas heating, Stage 2

= Tap 5

4. The IFC monitors PS2 for closure and if PS2 does

not close within 45 seconds, a PS2 open error will
be declared and the furnace will operate in 1

stage. If PS2 closes, 2

stage gas heating will

continue until the thermostat R-W2 contacts open.

otte

e:: If PS2 does not close within the 45 second time,

the IFC will wait 10 minutes and repeat steps 3 &
4. If on the third attempt during the same heating
call, PS2 does not close within the 45 second
proving time, the unit will run in 1

stage until

the thermostat contacts R-W2 open.

5. When the temperature raises enough to satisfy the

thermostat setting, contacts R-W2 will open, the 2

stage gas valve will close, the indoor blower motor
will ramp down to 1

stage, and the unit will

continue to run until R-W1 contacts open.

6. When the temperature raises enough to satisfy the

thermostat setting, contacts R-W1 will open.