American Standard 50A65-475 User manual

1
Gas Furnace Silicon
Nitride Ignitor Models
Gas Furnace Silicon
Nitride Ignitor Models
• Single and Two Stage Models
• Variable Speed Vent Models
• Variable Speed Blower Motor
• Test Procedures
• Direct Vent
• Single and Two Stage Models
• Variable Speed Vent Models
• Variable Speed Blower Motor
• Test Procedures
• Direct Vent
© 2001 American Standard Inc. All rights reserved.
© 2001 American Standard Inc. All rights reserved.

Note: This publication is general in nature and is intended for
INSTRUCTIONAL PURPOSES ONLY. It is not to be used for
equipment selection, application, installation, or specific service
procedures.

1
Contents
Model Nomenclature .......................................................................................................................................................... 3
Silicon Nitride Ignitor .......................................................................................................................................................... 4
Component Identification – Single Stage 80% Upflow/Horizontal ................................................................................... 6
Integrated Furnace Control – CNT02854 – Superseded to CNT03076 .............................................................................. 8
Integrated Furnace Control – CNT03076 ............................................................................................................................ 9
Single Stage 50A65-474 Sequence of Operation .............................................................................................................. 10
Wiring Schematic – Single Stage 80% and 90% ................................................................................................................ 11
Component Identification – Two Stage 80% Upflow/Horizontal ...................................................................................... 12
Integrated Furnace Control – CNT03077 ............................................................................................................................ 13
Two Stage 50M61-495 Sequence of Operation ................................................................................................................. 14
Wiring Schematic – Two Stage Heat .................................................................................................................................. 15
Component Identification – Two Stage/Two Speed Vent Motor and Variable Speed Indoor Motor .............................. 16
Integrated Furnace Control – CNT03078 ............................................................................................................................ 17
Two Stage Variable Speed Sequence of Operation .......................................................................................................... 18
Wiring Schematic – Two Stage Variable Speed Indoor Blower ........................................................................................ 19
Component Identification – Two Stage 90% Variable Speed Vent Motor and Four Speed Indoor Motor ..................... 20
Integrated Furnace Control – CNT02871 ............................................................................................................................ 21
Variable Speed Vent Motor ................................................................................................................................................. 22
Two Stage 50V65 Sequence of Operation ......................................................................................................................... 24
Two Stage Heat/Variable Speed Vent Motor/Standard Indoor Blower ............................................................................ 25
Component Identification – Two Stage 90% Variable Speed Vent Motor and Variable Speed Indoor Blower ............. 26
Integrated Furnace Control – CNT02536 ............................................................................................................................ 27
Two Stage 50A61 Sequence of Operation ......................................................................................................................... 28
Two Stage Variable Speed Vent Motor and Blower .......................................................................................................... 29
Two Stage/Variable Speed Vent and Variable Speed Blower Motor Models ................................................................... 30
White-Rodgers Self Diagnostic Features ........................................................................................................................... 31
Ignition Control Flash Codes .............................................................................................................................................. 32
Measuring Variable Speed Vent Motor RPM ..................................................................................................................... 33
Variable Speed Vent Motor Models .................................................................................................................................... 34
Diagnosing the Variable Speed Vent Motor with the Variable Speed Troubleshooter ................................................... 35
Diagnosing the Variable Speed Vent Motor/Manual Method ........................................................................................... 38
ECMTM2 Variable Speed Furnace Motor Quick Check ....................................................................................................... 40
V-Squared Furnace Motor – Control Board Schematic ..................................................................................................... 41
Vent Length Table for Variable Speed Vent Motor Models Only ...................................................................................... 42
Single Wire Twinning – For Models with Twin Terminals ................................................................................................. 43
Manifold Pressure Settings ................................................................................................................................................. 44
Furnace Pressure Switch Settings ...................................................................................................................................... 45
Direct Vent Pressure Switch Connections .......................................................................................................................... 46
Direct Vent Manifold Pressure Check ................................................................................................................................. 46
Cleaning the Air Inducer Stirring Fan ................................................................................................................................. 47
Legend – System Wiring ..................................................................................................................................................... 48

2
Diagnostic Codes
LED Flash Indicates
Slow Flash Normal Stand By.
Fast Flash Normal with a Call for Heat.
Continuous ON Internal Fault in the IFC.
2 Flashes System Lockout – No Flame. Total of three tries. Automatic reset in one hour.
3 Flashes Pressure Switch Error.
(Fault may be caused by a vent problem or a wiring connection in the switch
circuit.) On two speed furnaces, if there is a high heat pressure switch fault, the
IFC will not lock out. It will go back to low heat, cancel the three flash indication
for ten minutes and again try high heat.
4 Flashes Thermal Protection Device Open.
5 Flashes Flame being sensed with Gas Valve De-energized (Stuck Open). Vent motor and
indoor blower will be energized.
6 Flashes No Ground or Power Leads to Furnace Reversed, or Line Voltage Too Low.
7 Flashes 20 VAC at Gas Valve with No Call for Heat or if No Flame is Present;
Keep Vent Motor On.
8 Flashes Low Flame Sense Signal.
9 Flashes Ignitor Fault or Improper Ground or Low Voltage.
50A61-605 part #CNT02536 will only show the first seven flash codes.
If 24 VAC “R – B” is less than 20 VAC or greater than 30 VAC,
the control system will not function correctly.
IFC Diagnostic Codes

3
Model Nomenclature
✽UC040C924A
Furnace Configuration
U = Upflow/Horizontal
D = Downflow/Horizontal
Heating Input MBTUH
Airflow Capacity for Cooling
Major Design Change
Minor Design Change
Power Supply and Fuel
115 Volt
Natural Gas
Type
D = Induced Draft – 80% AFUE
E = 78%/80% AFUE
X = Direct Vent Condensing
Y = Direct Vent Condensing Variable Speed Blower
18 = 1 1/2 Tons 42 = 3 1/2 Tons
24 = 2 Tons 48 = 4 Tons
30 = 2 1/2 Tons 60 = 5 Tons
36 = 3 Tons
Example: 24 MBTUH = 2 Tons
400 CFM per Ton
2 Tons x 400 CFM/Ton = 800 CFM
V3 = 2 1/2 – 3 1/2 Tons, Variable Speed Motor
V4 = 3 – 4 Tons, Variable Speed Motor
V5 = 3 – 5 Tons, Variable Speed Motor
C = Single Stage
R = Two Stage
Example: 040 = 40,000 MBTUH
H
V
J
= Horizontal (Upflow/Horizontal Models Only)
= Variable Speed Vent Motor
= SiNi on 80% Furnaces Only
✽First letter may be A or T
1
Product Service Change
Part I.D.

4
Silicon Nitride Ignitor
Part # IGN 0104 Silicon Nitride Ignitor
Tungsten Element
SiNi
Insulators
Abbreviation ➠SiNi
Ignitor Composition:
1. Tungsten Paste Element
2. Silicon Nitride Ceramic Insulators

5
Silicon Nitride Ignitor
will lock out and cause the diagnostic status L.E.D.
to flash six times for control #50A61-605 CNT2536
only. Controls #50A65-474 CNT2854 and #50V65-495
CNT2871 will flash six times if the line polarity is
reversed and nine times if line voltage is low or
ground is not properly connected or the ignitor is open.
The maximum voltage permitted between line neutral
and ground is 10 volts; otherwise the IFC control will
not be able to properly vary the number of AC sine
wave cycles to the Silicon Nitride Ignitor.
This ignitor can only be checked by ohming in a cold
condition. A good ignitor reads 11 – 18 ohms. A bad
ignitor will have a much higher resistance (impedance).
60 Hertz AC Sine Wave
The ignitor used with this series of White-Rodgers con-
trols is constructed of a tungsten heater element and
silicon nitride ceramic insulators. The voltage rating of
the ignitor is 80 volts R.M.S., which is less than the line
voltage applied to the furnace; therefore, the control
will reduce the number of cycles it supplies to the SiNi
ignitor per second. The control checks the line voltage
constantly and when a call for heat is received the con-
trol sets the number of cycles it is going to supply to the
ignitor based on the line voltage it is reading. This re-
duced number of AC sine wave cycles per second re-
duces the effective voltage R.M.S. applied to the
SiNi ignitor per second. If the line voltage is low, the
number of cycles will go up, or if the line voltage is
high, the number of cycles is reduced.
After each successful ignition, the number of AC sine
wave cycles is reduced. The lower number of AC sine
waves reduces the effective voltage applied to the
ignitor. After each successful ignition attempt, the
burner lights, then the number of cycles is reduced.
During this learning program the number of cycles
will become too low and the gas fails to ignite. A retry
is initiated by the IFC and the number of AC sine
wave cycles is raised slightly to increase the ignitor
temperature.
Once a successful ignition attempt occurs during a
retry, that cycle count will be maintained for the next
255 calls of heat, or until another retry is called. The
IFC repeats the learning process again after 255 calls for
heat have been completed, or whenever power to the
furnace is cycled off and then on again.
This learning process is employed to provide the
most reliable ignition system possible. By lowering the
ignitor temperature, you will get the longest possible
service life from the rugged Silicon Nitride Ignitor. This
control requires the correct polarity of the 120 V.A.C.
wiring and a ground connection for proper operation.
If the line voltage is low, or the line polarity is reversed,
or the ground is not properly connected, the IFC control
CycleTurned Off
One Cycle
Time 1/60 of a Second
Number of cycles per second affects the effective
voltage or voltage R.M.S.
R.M.S. = Root – Mean – Square = The value assigned to
an alternating current or voltage that results in the
same power dissipation in a fixed resistance as DC
current or voltage of the same numerical value.
One or more cycles are turned off by the I.F.C. control to
control the R.M.S. voltage supplied to the silicon nitride
ignitor.

6
Component Identification
Single Stage 80% Upflow/Horizontal
INDUCED DRAFT
BLOWER (1 SPEED)
HIGH TEMPERATURE
LIMIT (TCO)
HIGH VOLTAGE
AND ACCESSORY
HOOK-UP
ROLL-OUT BI-METAL
RESETABLE
FLAME SENSOR
PRESSURE SWITCH
GAS VALVE
(ONE STAGE)
ROLL-OUT BIMETAL
RESETABLE
HOT SURFACE
IGNITOR
INSHOT BURNER
DOOR SWITCH
INTEGRATED
FURNACE CONTROL
TRANSFORMER
DIRECT DRIVE
BLOWER
REVERSE FLOW
SWITCH TCO-B

7
Component Identification
U2
K2 K1
E1
DS1
E20
1
4
2
3
12
97
1
8
5 AMPS
10 11
46
50A65474
CNT02854
LINE-N
CIR-N
E7
EAC-N
E9
HUM-N
E8
OFF
S1
ON
1
2
3
123
Q9
XMR-N
E10
E11
HUM-HXFMR-H
E13
LINE-H
E27
PARK
E28
PARK
E17
COOL-H
E14
EAC-H
E18
HEAT-H
E16
K3
DS1
3
5
2
Y W R G C
E34
CONDENSATE
TRAP
FLAME ROLL-OUT
SWITCH
(MANUAL RESET)
GAS VALVE
INDUCED DRAFT
BLOWER
TCO (LIMIT)
DOOR SWITCH
4 SPEED MOTOR
IGNITION
CONTROL
ELECTRICAL
JUNCTION BOX
PRESSURE
SWITCH
TRANSFORMER
HIGH TEMPERATURE
LIMIT SWITCH
BURNER
SIGHT GLASS
MOTOR
CAPACITOR
Single Stage 90% Upflow/Horizontal

8
Integrated Furnace Control CNT2854 – Superseded to CNT03076
Electrical Rating:
Input: 25 VAC, 60 Hz.
XFMR Sec, Current: 450 MA
IGN Output: 120 VAC, 2.0 A
MV Output: 24 VAC, 1.5 A
Cir. Blower Output: 120 VAC, 14.5 FLA, 26.0 LRA
Trial for Ignition Period: 4 Seconds
Ignitor Activation Period: Not Declared
Prepurge: 0 Seconds
Postpurge: 5 Seconds
Retries: 2
Recycles: 10
Cir. Blower on Delay: Heat 45 Seconds
Cir. Blower on Delay: Cool 2 Seconds
Cool “Off” Delay
SW1 Secs
On 0*
Off 80
Heat “Off” Delay
SW2 SW3 Secs
On Off 60
On On 100*
Off On 140
Off Off 180
* Factory Settings
U2
K2 K1
E1
DS1
E20
1
4
2
3
50A65474
CNT2854
CIR-N
E7
EAC-N
E9
HUM-N
E8
OFF
S1
ON
1 2 3
Q9 E10
E11
HUM-HXFMR-H
E13
LINE-H
E27
PARK
E28
PARK
E17
COOL-H
E14
EAC-H
E18
HEAT-H
E16
K3
DS1
Y W R G C
E34
121110
987
6
54
321
5 AMPS
1
2
3
4
LINE-IN
XEMR-N
Plug # E1
PINS OUT
12 PIN CONNECTOR
1. HLO High Limit Output
2. FP Flame Probe
3. TH 24V Hot
4. Not Used
5. Not Used
6. TR 24V Return
7. HLI High Limit Input
8. GND Ground
9. MV COM Main Valve Common
10. PS Pressure Switch
11. Not Used
12. MV Main Valve
4 PIN CONNECTOR
1. IND Inducer
2. IGN Ignitor
3. IND-N Inducer Neutral
4. IGN-N Ignitor Neutral
Plug # E20
1. IND-H
2. IGN-H
3. IND-N
4. IGN-N
Used on 80% and 90% Furnaces
Single Stage Heat – Silicon Nitride Hot Surface Ignitor
Single Speed Vent Motor and Standard Four Speed Blower

9
Integrated Furnace Control – CNT03076
U2
K2 K1
E1
DS1
E20
CIR-N
E7
EAC-N
E9
HUM-N
E8
OFF
S1
ON
1 2 3
Q9 E10
E11
HUM-HXFMR-H
E13
LINE-H
E27
PARK
E28
PARK
E17
COOL-H
E14
EAC-H
E18
HEAT-H
E16
K3
DS2
5 AMPS
1
2
3
4
LINE-IN
XFMR-N
50A65-475
CNT03076
TWIN Y W R G C
TWIN Y W R G C
E34
Used on 80% and 90% Furnaces
Single Stage Heat – Silicon Nitride Hot Surface Ignitor
Single Speed Vent Motor and Standard Four Speed Blower with
Single Wire Twinning Feature

10
White-Rodgers Integrated Furnace
Controls 50A65-474 with Silicon Nitride
Hot Surface Ignitor (SiNi HSI) – Part No.
CNT02854, Superseded to CNT03076
When the disconnect 1is in the “ON” position, power
is applied through the blower door interlock switch 6
to the control line voltage input terminal 8and out of
the control to the primary side of the control
transformer “XFMR” e. The low voltage side of the
transformer supplies 24 volts to the control through
terminals “TH” oand “TR” i. Control terminal “R” ;
supplies 24 volts to the “R” terminal of the room
thermostat.
Once power is applied, the control flashes the LED
“ON” for one second and performs a self check
routine. Following the normal system check, the
control flashes the LED light once per second
continuously (slow flash) while in stand-by.
On a call for heat, 24 volts are applied from the room
thermostat’s terminal “W” to the “W” terminal ;on
the control. The control checks and confirms normally
closed contacts at the temperature cut out “TCO” f, or
the fuse link auxiliary limit (downflow and some
upflow/horizontal models) j, the flame roll-out switch
jand normally open contacts of the safety pressure
switch “PS” f. With all safety and control switches in
their proper position, the control will energize the
induced draft motor yand flash the LED light two
times per second continuously (fast flash) during a
call for heat.
When the safety pressure switch “PS” fcloses, the
control begins the ignition sequence. The SiNi hot
surface ignitor yis energized for several seconds
(see page 11) allowing the thermal element to heat
Single Stage 50A65-474 Sequence of Operation
up. The control then switches on 24 volts to the gas
valve “MV” terminal #1 a. The redundant and main
solenoids are energized allowing gas flow and main
burner ignition. When flame current is detected by
the control through its terminal “FP” k, the 45 second
indoor blower motor delay on timing begins. Flame
failure response time is set for two seconds. After
flame has been established for ten seconds, the flame
failure response time is reset for 0.7 seconds. If
flame current is not sensed by the control kwithin
four seconds, the trial for ignition period, the redundant
and main gas valve solenoids aare de-energized.
The control will begin an interpurge cycle and may
add additional AC sine wave cycles to the hot
surface ignitor warm-up cycle (see SiNi HSI write up).
The control energizes the gas valve afor the second
attempt to establish main burner ignition. If flame
current is not sensed by the control on the second
retry within the trial for ignition period, the control
will repeat the previous cycle one additional time
before locking out.
At the end of the indoor blower delay on time, line
voltage is applied at the controls terminal “HEAT” 5
energizing the indoor blower motor at heating fan
speed, supplying warm air to the space.
When the thermostat is satisfied, the valve’s redundant
and main solenoids aare de-energized, extinguishing
main burner flame. Once the control senses loss of
flame current (0.7 sec.) k, the induced draft motor t
is de-energized after a five second post-purge cycle.
The indoor blower motor delay off timing begins. At
the completion of the fan delay off timing, the
indoor blower motor 5is de-energized and the cycle
is complete.

11
Wiring Schematic
C
M
2
1, 3
FLAME
SENSOR
GR
GND
GAS VALVE
120 VOLT, 60 HZ., 1 PH.
POWER SUPPLY
PER LOCAL CODES
1
2
3
4
5
6
7
8
9
q
w
e
r
t
y
u
i
o
p
a
s
d
f
g
h
j
k
l
;
z
0
I.D.
BLOWER
MTR.
N H
GR
GR
GR
24V
GND
BK
“A”
“B”
“C”
BK/1
BK/4
BK/3
BK/2
WH
WH/1
WH/4
OPTIONAL
COOL
HEAT
PARK
PARK
LINE
XFMR
EAC
HUM
CIR N
LINE N
XFMR N
EAC N
HUM N
6
3
9
12
4
5
10
7
11
1
2
8
TR
TH
MV
MV
PS
HLI
HLO
FP
GND
OR
YL
GND
GND
BK
WH/1
CF
BR BR
DOOR
SWITCH
GND
HOT 120VAC
70 –80 VAC
NEUTRAL
NEUTRAL 120VAC
DIP
SWITCH
ON
DIAGNOSTIC
LED
OFF
123
BK
WH
SINI IGNITOR
YL/2
YL/3
YL/4
2
TCO
YL/1
YTWIN W G RC
TO THERMOSTAT
1
2
3
4
IND
IGN
IND N
IGN N
BK/6
BK/5
WH/6
WH/5
BL
RD
BL/1
RD/1
1USED ON 90% FURNACE MODELS ONLY.
2DIRECT VENT MODELS HAVE ONE MANUAL
RESET FLAME ROLL-OUT BI-METAL SWITCH
INSTEAD OF TWO.
3SOME MODELS MAY HAVE A FUSE LINK HERE
OR A NON-RESETABLE BI-METAL SWITCH.
TCO-B
YL/5
WH
PRESSURE
SWITCH
TNS
120V
IND.
MTR.
TCO-B
1
BK BK
WH WH
HOT 120VAC
2 3
FLAME ROLL-OUT
SWITCH
FUSE
Single Stage 80% and 90%

12
Component Identification
Two Stage 80% Upflow/Horizontal
INDUCED DRAFT
BLOWER (2 SPEED)
HIGH TEMPERATURE
LIMIT (TCO)
HIGH VOLTAGE
AND ACCESSORY
HOOK-UP
ROLL-OUT BI-METAL
RESETABLE
FLAME SENSOR
1ST STAGE
PRESSURE SWITCH
2ND STAGE
PRESSURE SWITCH
GAS VALVE
(2 STAGE)
ROLL-OUT BI-METAL
RESETABLE
HOT SURFACE
IGNITOR
INSHOT BURNER
DOOR SWITCH
INTEGRATED
FURNACE CONTROL
TRANSFORMER
4 SPEED
BLOWER
REVERSE FLOW
SWITCH TCO-B

13
E1
F1
3
HUMHUMCIRCEACXFMRLINE XFMR LINE CRC PARK COOL EAC HI HEAT LO HEAT
HUMHUMCIRCEACXFMRLINE XFMR LINE CRC PARK COOL EAC HI HEAT LO HEAT
6
9
12
1
4
7
10
5
1 2 3
1
2
3
4
OFF ON
S1
K1
K2
K7
K3
E4
Q22
C17
U3
U1
K8
K6
BLK/TWIN W2 W1 R G B Y YLO O
BLK/TWIN W2 W1 R G B Y YLO O
K8
RV2
HOTNEUTRAL
DS1
50M61-495
CNT03077
Integrated Furnace Control – CNT03077
DIP SWITCH (S1)
Cool “Off” Delay
SW1 Secs
On* 80
Off 0
Heat “Off” Delay
SW2 SW3 Secs
On Off 60
On* On 100
Off On 140
Off Off 180
* Factory Settings
Plug # E4
5. IGN-N
4. IND-N
3. IND-LO
2. IND-HI
1. IGN HOT
Plug # E1
PINS OUT
12 PIN CONNECTOR
1. MVH High Main Valve
2. PS2 2nd Stage Pressure Switch
3. FP Flame Probe
4. GND Ground
5. TH 24V Hot
6. HLI High Limit Input
7. MVL Low Main Valve
8. MVCOM Main Valve Common
9. TR 24V Return
10. GND Ground
11. HLO High Limit Output
12. PSI 1st Stage Pressure Switch

14
Two Stage 50M61-495 Sequence of Operation
White-Rodgers Integrated Furnace Control
50M61-495 Models
When the service disconnect 1is in the “ON” position,
power is applied through the blower door interlock
switch 6to the controls line voltage input terminals 8
and out of the control to the primary side of the
control transformer “XFMR” u. The secondary side
of the control transformer supplies 24 volts to the
control through terminal “TH” and “TR” po. Control
terminal “R” ;supplies 24 volts to the “R” terminal
of the room thermostat.
Once power is applied, the control flashes the LED
light “ON” for one second and performs a self check
routine. Following the normal system check, the
control flashes the LED one time per second (slow flash)
continuously while in stand-by.
On a call for heat, 24 volts are applied from the room
thermostat’s “W1” terminal to the “W1” terminal z
on the control. The control checks and confirms
normally closed contacts at the temperature cut
out“TCO” j, auxiliary limit (downflow and
some upflow/horizontal models), the flame roll-out
bi-metal control (two bi-metal controls are now used
on downflow/horizontal models) land normally open
contacts at the safety pressure switch #1 j. With all
safety and control switches in their proper position,
the control will energize the induced draft motor on
high speed wand flash the LED two times per second
continuously (fast flash) during a call for heat.
When safety pressure switch “#1” jcloses, the
control switches the induced draft motor to low speed w
and begins the ignition sequence. The hot surface
|ignitor wis energized for several seconds (see note)
allowing the thermal element to heat up. The control
then switches 24 volts to its “MVL” and “MV COM” g
terminals to terminals #1 gand #2 fon the gas
valve. The redundant and main solenoids are energized
allowing gas flow and main burner ignition. When
flame current is sensed by the control through its
“FP” ;terminal, the 45 second indoor blower motor
time delay “ON” begins. Flame failure response
time is set for two seconds. After flame has been
established for ten seconds, the flame failure response
time is reset for 0.7 seconds. If flamed current is not
sensed by the control within the trial for ignition period
(see note), the main valve low and redundant gas
valve solenoids ga are de-energized. The control
will begin an interpurge cycle and adds additional
seconds to the hot surface ignitor warm-up timing
(see note). The control energizes the gas valve for the
second attempt to establish main burner ignition. If
again flame current is not sensed by the control within
the trial for ignition period (see note), the control will
repeat the previous cycle before locking out. At the
end of the indoor blower motor delay “ON” timing, line
voltage is applied at control terminal “HEAT LO” 6
energizing the indoor blower motor at low heat
fan speed, supplying warm air to the space.
If the temperature in the space continues to fall, the
thermostat second stage contacts “W2” close.
24 volts are switched from thermostat terminal “W2” to
the “W2” terminal zon the control. A 30 second,
2nd stage recognition time delay begins. At the end of
the 30 second delay, the induced draft motor is
switched to high speed wcausing pressure switch #2 d
to close. When pressure switch #2 closes, 24 volts are
switched from control terminal “MVH” dto the gas
valve terminal #3 denergizing the second stage
solenoid allowing increased gas flow to the
burners. At the same time, the indoor blower motor
is switched to high heat fan speed 7.
When second stage thermostat contacts “W2” satisfy,
the induced draft motor is switched back to low speed w
causing pressure switch #2 dto open, breaking the
circuit to the second stage gas valve solenoid d. Gas
flow is reduced to the burners. The indoor blower
motor will switch back to low heat fan speed after a
30 second delay 6.
When first stage thermostat contacts “W1” satisfy,
the main valve low and the redundant gas valve
solenoids gare de-energized extinguishing main
burner flame. Once the control senses the loss of
flame current (0.7 sec.) ;, the induced draft motor w
is de-energized after a five second post-purge cycle.
The indoor blower motor “OFF” timing begins. At the
end of the indoor blower motor “OFF” timing, the
indoor blower motor is de-energized and the cycle
is complete.
Note: See Timing Chart for details or the Integrated Furnace
Control Label.

15
Wiring Schematic
Two Stage Heat (White-Rodgers 50M61-495 Series Integrated Furnace Control)
GAS VALVE
120 VOLT, 60 HZ., 1 PH.
POWER SUPPLY
PER LOCAL CODES
1
2
3
4
5
6
7
8
9
q
w
e
r
t
y
u
i
o
p
a
s
d
f
g
h
j
k
l
;
z
0
I.D.
BLOWER
MTR.
N H
GR
GR
GR
24V
TNS
GR
IND.
MTR.
1
2
3
4
5
IGN
IND HI
IND LO
IND N
IGN N
GND
BK/5
BK/6
RD/6
WH/6
WH/5
BK
“A”
“B”
“C”
BK/1
BK/4
BK/2
BK/3
OPTIONAL
COOL
PARK
HEAT LO
HEAT HI
LINE
XFMR
EAC
HUM
WH/1
WH/4
WH
LINE N
XFMR N
CIR N
EAC N
HUM N
9
5
4
2
1
8
7
10
12
6
11
3
TR
TH
GND
PS2
MVH
MVCOM
MVL
GND
PSI
HLI
HLO
FP
BL
RD
BR
OR/1
BL/1
RD/1
OR
YL
YL/5
WH
GND
GND
BK
WH/1
CF
BR BR
DOOR
SWITCH
GND
50M51-495
INTEGRATED FURNACE CONTROL
HOT 120VAC
70 –80 VAC
HOT 120 VAC
NEUTRAL
120VAC
DIP
SWITCH
ON
DIAGNOSTIC
LED
OFF
123
120V
WH
WH
SINI
IGNITOR
PRESSURE SWITCH
2ND STAGE
BR/1
HI
B/C
LO
3
2
1PRESSURE SWITCH
1ST STAGE
FLAME
SENSOR
GND
BI-METAL FLAME
ROLL-OUT
1
BI-METAL
FLAME
ROLL-OUT
YL/2
YL/3
YL/4
1TCO-B
TCO
TCO
YL/1
1SOME MODELS MAY HAVE A FUSE LINK HERE
OR A NON-RESETABLE BI-METAL SWITCH.
W1 W2 R GBY
TO THERMOSTAT
BK/TWIN
FUSE

16
Component Identification
80% Two Stage/Two Speed Vent Motor and Variable Speed Indoor Motor
INDUCED DRAFT
BLOWER (2 SPEED)
HIGH TEMPERATURE
LIMIT (TCO)
HIGH VOLTAGE
AND ACCESSORY
HOOK-UP
ROLL-OUT BI-METAL
RESETABLE
FLAME SENSOR
1ST STAGE
PRESSURE SWITCH
2ND STAGE
PRESSURE SWITCH
GAS VALVE
(2 STAGE)
ROLL-OUT BI-METAL
RESETABLE
HOT SURFACE
IGNITOR
INSHOT BURNER
DOOR SWITCH
INTEGRATED
FURNACE CONTROL
TRANSFORMER
VARIABLE SPEED
MOTOR
REVERSE FLOW
SWITCH TCO-B

17
Integrated Furnace Control – CNT03078
F1
HUMHUMCIRCEACXFMRLINE XFMR LINE CRC PARK COOL EAC HI HEAT LO HEAT
HUMHUMCIRCEACXFMRLINE XFMR LINE CRC PARK COOL EAC HI HEAT LO HEAT
5
1 2
1
2
3
4
OFF ON
S1
1 2 3 4
1 2 3 4
5 6 7 8
5 6 7 8
ON
OFF
CFM
K1
K2
K7
K3
E4
Q22
C17
U3
U1
K8
K6
BLK/TWIN W2 W1 R G B Y YLO O
BLK/TWIN W2 W1 R G B Y YLO O
K8
RV2
HOTNEUTRAL
DS1
E1
3
6
9
12
1
4
7
10
8
16
7
15
6
14
5
13
4
12
3
11
2
10
1
9
Plug # P1
W14
BK JUMPER
50V61-507
CNT03078
DIP SWITCH (S1)
Heat “Off” Delay
SW1 Secs
SW2 SW3 Secs
On Off 60
On* On 100
Off On 140
Off Off 180
* Factory Settings
Plug # E4
5. IGN-N
4. IND-N
3. IND-LO
2. IND-HI
1. IGN HOT
Plug # E1
PINS OUT
12 PIN CONNECTOR
1. MVH High Main Valve
2. PS2 2nd Stage Pressure Switch
3. FP Flame Probe
4. GND Ground
5. TH 24V Hot
6. HLI High Limit Input
7. MVL Low Main Valve
8. MVCOM Main Valve Common
9. TR 24V Return
10. GND Ground
11. HLO High Limit Output
12. PSI 1st Stage Pressure Switch
16 PIN CONNECTOR
1. Earth Ground
2. Low Heat Speed Select Output
3. Earth Ground
4. Delay Dip Switch
5. Cool Dip Switch
6. YLO
7. Adjust Dip Switch
8. Earth Ground
9. “O” Input From Thermostat
10. BK Output
11. Heat Dip Switch
12. TH (24VDC)
13. High Heat Speed Select Output
14. Y
15. Enable Output
16. CFM LED

18
Two Stage Variable Speed Sequence of Operation
White-Rodgers 50V61 Series Integrated
Furnace Control
When the service disconnect 1is in the “ON” position,
power is applied through the blower door interlock
switch 3to the controls line voltage input terminals 6and
out of the control to the primary side of the
control transformer 9,and from the “CIRC” 7
terminal to the ECMTM Fan Motor 3. The secondary
side of the control transformer supplies 24 volts to the
control through terminal “TH” and “TR” we. Control
terminal “R” gsupplies 24 volts to the “R” terminal of
the room thermostat.
Once power is applied, the control flashes the LED
light “ON” for one second and performs a self
check routine. Following the normal system check,
the control flashes the LED one time per second (slow
flash) continuously while in stand-by.
On a call for heat, 24 volts is applied from the room
thermostats “W1” terminal to the “W1” terminal g
on the control. The control checks and confirms
normally closed contacts at the temperature cut
out “TCO” a, auxillary limit (downflow and some
upflow/horizontal models), the flame roll-out bi-metal
control (two bi-metal controls are now used on
downflow/horizontal models) aand normally open
contacts at the safety pressure switch #1 p. With all
safety and control switches in their proper position,
the control will energize the induced draft motor
on high speed 9and flash the LED two times per
second continuously (fast flash) during a call for heat.
When safety pressure switch “#1” pcloses, the
control switches the induced draft motor to low
speed 0and begins the ignition sequence. The hot
surface ignitor 9is energized for several seconds
allowing the thermal element to heat up. The control
then switches 24 volts to its “MVL” iand “MV
COM” uterminals to terminals #1 iand #2 uon
the gas valve. The redundant and main solenoids are
energized allowing gas flow and main burner ignition.
When flame current is sensed by the control through
its “FP” fterminal, the 45 second indoor blower
motor time delay “ON” begins. Flame failure response
time is set for two seconds. After flame has been
established for ten seconds, the flame failure response
time is reset for 0.7 seconds. If flamed current is not
sensed by the control fwithin the trial for ignition
period, the main valve low and redundant gas valve
solenoids iare de-energized. The control will begin
a 30 second interpurge cycle and adds additional
seconds (see note) to the hot surface ignitor warm-up
timing. The control energizes the gas valve for the
second attempt to establish main burner ignition.
If again flame current is not sensed by the control
within the trial for ignition period (see note), the
control will repeat the previous cycle before locking
out. At the end of the indoor blower motor delay
“ON” timing, the microprocessor will close the
normally open K3 relay contacts j completing a
24 volt signal circuit to pin #15 of the ECMTM motor,
signaling it to turn on and run at the low heat blower
speed, supplying warm air to the space. 24 volts
W1 gterminal from the thermostat is also applied
to the ECMTM motor harness pin #12 h, which signals
the ECMTM motor to run at the low heat speed setting.
If the temperature in the space continues to fall, the
thermostat second stage contacts “W2” close.
24 volts are switched from thermostat terminal “W2” to
the “W2” terminal gon the control. A 30 second,
2nd stage recognition time delay begins. At the end
of the 30 second delay, the induced draft motor is
switched to high speed 9causing pressure switch
#2 oto close. When pressure switch #2 closes,
24 volts is switched from control terminal “MVH” oto the
gas valve terminal #3 oenergizing the second
stage solenoid, allowing increased gas flow to the
burners. At the same time, the microprocessor
closes the normally open K1 relay contacts j
completing a 24 volt signal circuit to pin #13 k of the
ECMTM2 motor signaling the indoor blower motor to
run at the high heat blower speed.
When second stage thermostat contacts “W2” satisfy,
the induced draft motor is switched back to low
speed 0causing pressure switch #2 yto open,
breaking the circuit to the second stage gas
valve solenoid y. Gas flow is reduced to the burners.
The indoor ECMTM blower motor 4will be switched
back to the low heat fan speed after a 30 second delay.
When first stage thermostat contacts “W1” satisfy,
the main valve low and the redundant gas valve
solenoids iare de-energized extinguishing main
burner flame. Once the control senses the loss of
flame current (0.7 sec.) f, the induced draft motor 9
is de-energized after a five second post-purge cycle.
The indoor blower motor “OFF” timing begins. At the
end of the indoor blower motor “OFF” timing, the indoor
blower motor is de-energized and the cycle is complete.
Note: See Timing Chart for details or the Integrated Furnace
Control Label.