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Computer board assembly
240HX3/340HX3
Wiring diagram
240HX3/340HX3
BL
BL
O.H.C.F
Hi-limit
switch
Drain plug
detector
Hi-limit switch
for exhaust
Drain plug
detector
Exhaust
thermistor
Gas
Propor-
�onal
Valve
MAX bu�on
MIN bu�on
Increase bu�on
Decrease bu�on
540HX3
FM
Y
Flame rod
Ground
AFR rod
Gas
Propor-
�onal
Valve
Y
Bypass
Valve
DIP switches
Green LED
MAX bu�on
MIN bu�on
Increase bu�on
701
711
708
714
721
716
408
407
722
061
707
SV3
R
SV2
708
711
G
SV1
PCB
LB
MV
BL
73
BL
53
BL
9
3
BL
BL
240HX3/340HX3 Outdoor Only
721
G
G
G
G
721
240HX3/340HX3 Indoor
W
Only
W
G
G
W
G
W
W
W
240HX3/340HX3
Indoor Only
714
408
W
R
407
W
1
2
3
4
5
6
7
8
9
10
OFF
Green LED
DIP switches
IG
P
Igniter rod
P
711
R
BL
O
103
W
O
G
Y
3
708
9
709
53
73
R
W
714
R
715
W
BL
BR
721
540HX3
Indoor
Only
BK
BK
Heat
BK
thermistor
BK
Inlet thermistor
715
BK
Outlet thermistor
Decrease bu�on
540HX3
701
713
714
715
103
709
716
402
402
715
IG
P
P
Heater
Igniter rod
713
Thermostat
BK
BK
W
W
713
G
SW
Ground
Surge
box
W
FM
Y BL O
W
103
BK
R
704
AFR rod
709
Y
G
O
120 VAC
Flame rod
G
Ground
402
Flow
Ground
R
W
Sensor
BK
402
BK
R
BK
BL R
Built-in controller
W
Outlet thermistor
BK
BK
Inlet thermistor
BK
707
Remote controller
Heater
PCB
713
713
Thermostat
713
BK
W
W
G
SW
Ground
Hi-
MV
BL
limit
BL
switch
W
SV1
BL BL
BL
BL
SV2
O.H.C.F
BL
LB
G
SV3
R
Flow
402
R
BK
Adjust-
Ground
ment
Flow
R
402
Sensor
W BK
W
715
BK
W
BK
540HX3
Indoor
Only
W
BK
Hi-limit switch
W
for exhaust
W
Drain plug detector
G
G
exchanger
Exhaust thermistor
W W
57
Page
Owner's Guide
Components Diagram
709
711
708
713
103
402
402
715
707 722
721
Y
240HX3/340HX3 Outdoor Only
Heater
Y
Y
Y
Heater
BK
Heater
Y
240HX3/340HX3 Indoor Only
BK
Heater
Y
W
Heater
Heater
Y
713
713
Flow
Adjust-
ment
Valve
722
Y
540HX3 Outdoor Only
Heater
Y
Y
Y
Heater
BK
Heater
Y
BK
540HX3 Indoor Only
BK
Heater
Y
Surge
W
box
Heater
Heater
BK
Y
713
713
120 VAC
G
704
1
2
Parent
W BL
Built-in controller
722
R BK
Remote controller
707
540HX3
Outdoor
Only
721
Drain plug
G
G
detector
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