13
WIRING DIAGRAM FOR 2-STAGE FURNACE
Two Stage Furnace
Models 1522 & 2334
WITH DOOR AND WITHOUT DOOR
Two Stage Furnace
Model 2540
WITH DOOR AND WITHOUT DOOR
1
6
+12
VDC
–12
VDC
5 4
Thermostat
Dual
Cont.
Ignition
Control
5ON-12
Low
Valve
Brown
Green
Yellow
Geen
Yellow
Red
Red
Red
Red
Green
Yellow
GND
White
Black
White
Blue
Blue
Blue
LS
SS
PS
MOT
C.B.
Orange
Main
Valve
GV
Redundant
Valve
3 2 1
2 3 4 5 6
Case
Bulk-
head
CB = Circuit Breaker
GND = Ground
GV = Gas Valve
HV = High Voltage
EL = Electrode
MOT = Blower Motor
SS = Sail Switch
LS = Limit Switch
PS = Power Switch
NOTE: The Power Switch (PS)
does not control the air
conditioning system
thermostat function.
HV
EL
1
6
+12
VDC
–12
VDC
5 4
Thermostat
Dual
Cont.
Ignition
Control
5ON-12
Low
Valve
Brown
Green
Yellow
Geen
Yellow
Red
Red
Red
Red
Green
Yellow
GND
White
Black
White
Blue
Blue
Blue
LS
SS
PS/CB
MOT
Orange
Main
Valve
GV
Redundant
Valve
3 2 1
2 3 4 5 6
HV
EL
GND = Ground
GV = Gas Valve
HV = High Voltage
EL = Electrode
MOT = Blower Motor
SS = Sail Switch
LS = Limit Switch
PS/CB = Power Switch/
Circuit Breaker
NOTE: The Power Switch (PS)
does not control the air
conditioning system
thermostat function.
1
6
+12
VDC
–12
VDC
5 4
Thermostat
Dual
Cont.
Ignition
Control
5ON-12
Low
Valve
Brown
Yellow
Geen
Yellow
Red
Red
Red
Red
Green
Yellow
GND
White
Black
White
Blue
Blue
Blue
LS
SS
PS
MOT
C.B.
Orange
Main
Valve
GV
Redundant
Valve
3 2 1
2 3 4 5 6
Case
Bulk-
head
CB = Circuit Breaker
GND = Ground
GV = Gas Valve
HV = High Voltage
EL = Electrode
MOT = Blower Motor
SS = Sail Switch
LS = Limit Switch
PS = Power Switch
NOTE: The Power Switch (PS) does not
control the air conditioning system
thermostat function.
HV
EL
1
6
+12
VDC
–12
VDC
5 4
Thermostat
Dual
Cont.
Ignition
Control
5ON-12
Low
Valve
Brown
Yellow
Geen
Yellow
Red
Red
Red
Red
Green
Yellow
GND
White
Black
White
Blue
Blue
Blue
LS
SS
PS/CB
MOT
Orange
Main
Valve
GV
Redundant
Valve
3 2 1
2 3 4 5 6
HV
EL
GND = Ground
GV = Gas Valve
HV = High Voltage
EL = Electrode
MOT = Blower Motor
SS = Sail Switch
LS = Limit Switch
PS/CB = Power Switch/Circuit Breaker
NOTE: The Power Switch (PS) does not
control the air conditioning system
thermostat function.
2-Stage Furnace Diagnostics
NUMBER OF LED FLASHES
DIAGNOSTIC INFORMATION
LOCKOUT
1
Low Input voltage
SOFT
2
Ignition Failure
SOFT
3
Open High Limit
SOFT
4
Stuck Sail Switch
HARD
5
Module Fault
HARD
NOTE
: A
SOFT
lockout is a condition that is timed and will make additional
attempts to correct the problem. A
HARD
lockout requires reset of
the thermostat or turning the power switch off then back on.
DIAGNOSTIC CHART
A diagnostic LED is located inside the exterior access cover
on the outside edge of the horizontal (2) stage control
board. The following graph defines the codes.
An Excalibur 2-Stage furnace must use an
Atwood Digital Thermostat.
