Trane S8B1A040M3PSC Installation, Operation And Maintenance Manual page 65

DEFINITION
An error has occurred with the PS1 indica ng that the pressure
switch is either open when it should be closed.
In most cases, the pressure switch is not the problem.
NOTE: Verify pressure switch wiring and tube rou ng
are correct.
PS1 Open errors can occasionally happen when wind
gusts occur.
S8X2 Only
The IFC will a empt to close both PS1 and PS2 and
nd
operate on 2 stage during such an event.
S8XB-SVX001-1B-EN
3.2 Fault Code
Cycle power to the furnace
and call for 1
PS1 is closed
Yes
& is good
PS1 is closed & is
NO
good
Verify PS hose(s) is connected, and
that flue piping has no obstruc on.
st
stage heat.
Is the inducer
NO
motor running?
YES
Does the igniter
glow within 60
Verify no voltage at IFC at
seconds?
NO
Is 24 volts present,
measured across PS1
(orange to yellow)?
See Note #1
YES
Is pressure greater
than pressure switch
YES
label?
See Note #2
NO
Possible Causes
T T r r o o u u b b l l e e s s h h o o o o t t i i n n g g
Note #1
24 volts = Open Switch
0 volts = Closed Switch
Note #2
Measured pressure is
nega ve, greater than refers
to magnitude only.
S8B1 / S8X1 measure BK to WH at
the inducer motor and
IND-H – IND-N at IFC
Is ~120VAC measured
from RD to WH on the
YES
inducer motor within
60 seconds of the W1
call?
**
NO
IND-LO - IND-N
Replace IFC
**
Replace pressure switch.
Check opera on.
**
Replace inducer
assembly
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