Emerson White-Rodgers 21D83M-843 User manual

21D83M-843
Integrated Single Stage
Furnace Control Replacement Kit
FAILURETO READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY BEFORE
INSTALLING OR OPERATING THIS CONTROL COULD CAUSE PERSONAL
INJURY AND/OR PROPERTY DAMAGE.
DESCRIPTION
PRECAUTIONS
INSTALLATION INSTRUCTIONS
Kit includes:
1 – 50A66-843 ignition control board
1 – Wiring harness (9-pin to 12-pin)
1 – Wiring harness (4-pin to 6-pin)
1 – Mounting panel
4 – Stand-off fasteners
1 – Circuit breaker
1 – 4" blue wire
2 – Wiring diagrams
Installation should be done by a qualified heating and air
conditioning contractor or licensed electrician.
If in doubt about whether your wiring is millivolt, line, or
low voltage, have it inspected by a qualified heating and
air conditioning contractor or licensed electrician.
Do not exceed the specification ratings.
All wiring must conform to local and national electrical
codes and ordinances.
This control is a precision instrument, and should be
handled carefully. Rough handling or distorting compo-
nents could cause the control to malfunction.
Following installation or replacement, follow manufacturer’s
recommended installation/service instructions to ensure
proper operation.
WARNING
!
Failure to comply with the following warnings
could result in personal injury or property damage.
FIRE HAZARD
• Do not exceed the specified voltage.
• Replace existing control with exact model
and dash number.
• Protect the control from direct contact with
water (dripping, spraying, rain, etc.).
• If the control has been in direct contact with
water, replace the control.
• Label all wires before disconnection when
servicing controls. Wiring errors can cause
improper and dangerous operation.
• Route and secure wiring away from flame.
SHOCK HAZARD
• Disconnect electric power before servicing.
• Ensure proper earth grounding of appliance.
• Ensure proper connection of line neutral and
line hot wires.
EXPLOSION HAZARD
• Shut off main gas to appliance until installa-
tion is complete.
CAUTION
!
Do not short out terminals on gas valve or primary
control. Short or incorrect wiring may damage
the thermostat.
The kit includes the 50A66-843 which is an automatic gas
interrupted ignition control that employs a microprocessor
to continually monitor, analyze, and control the proper
operation of the gas burner, inducer, and fan.
These controls incorporate system fault analysis for quick
gas flow shut-off, coupled with automatic ignition retry
upon sensing a fault correction.
Lennox White-Rodgers Page Reference
10M9301
12L6901
32M8801
56L8401
50A65-120
50A65-121
3 PROCEDURE 1
Figure 1, Picture
1, Table 1, Wiring
Diagram 5001-6973
24L8501
63K8901
97L4801
50A62-120
50A62-121
50A62-820
4 PROCEDURE 2
Figure 1, Picture
2, Table 2, Wiring
Diagram 5001-6972
100925-01
100925-03
17W9201
23W5101
30W2501
69M0801
69M1501
83M00
21D83M-843
50A66-122
50A66-123
5 PROCEDURE 3
The 21D83M-843 kit will replace the following Controls:
Follow instructions for replacement of your model num-
ber under the heading INSTALLATION.
PART NO. 37-7337C
Replaces 37-7337B
1515
white-rodgers.com
emersonclimate.com

2
SPECIFICATIONS
ELECTRICAL RATINGS [@ 77°F (25°C)]:
Input Voltage: 25 VAC 50/60 Hz
Max. Input Current @ 25 VAC: 0.45 amp
Relay Load Ratings:
Valve Relay: 1.5 amp @ 25 VAC 50/60 Hz 0.6 pf
Ignitor Current: 2.0 amp @ 80 VAC
Inducer Relay: 2.2 FLA–3.5 LRA @ 120 VAC
Circulator Relay: 14.5 FLA–25.0 LRA @ 120 VAC
Flame Current Requirements:
Minimum current to insure flame detection:0.25 µa DC*
Maximum current for non-detection: 0.1 µa DC*
Maximum allowable leakage resistance: 100 M ohms
*Measured with a DC microammeter in the flame probe lead
OPERATING TEMPERATURE RANGE:
TIMING SPECIFICATIONS
(All times are in seconds, unless noted otherwise
Event Definition 50A66-843
Pre-Purge The period of time intended to allow for the dissipation of any unburned
gas or residual products of combustion at the beginning of a furnace
operating cycle prior to initiating ignition
15
Trial for Ignition
Period (TFI)
The period of time between initiation of gas flow and the action to
shut off the gas flow in the event of failure to establish proof of the
supervised ignition source or the supervised main burner flame.
4
Ignition Activation
Period (IAP)
The period of time between energizing the main gas valve and
deactivation of the ignition means prior to the end of TFI
4
Retries The additional attempts within the same thermostat cycle for ignition
when the supervised main burner flame is not proven within the first
trial for ignition period.
4 times
Valve Sequence
Period
Valve sequence period equals 4 seconds trial for ignition period x
(1 initial try + 2 retries) + 12 seconds.
20
Interpurge The period of time intended to allow for the dissipation of any unburned
gas or residual products of combustion between the failed trial for
ignition and the retry period.
15
Post-Purge The period of time intended to allow for the dissipation of any unburned
gas or residual products of combustion at the end of a furnace burner
operating cycle. Post-purge begins at the loss of flame sense.
5
Lockout Time ANSI standard rated module timing. 250
Heat Delay-To-Fan-On The period of time between proof of the supervised main burner flame
and the activation of the blower motor at Heat speed.
45
Heat Delay-To-Fan-Off* The period of time between the loss of a call for heat and the
deactivation of the blower motor at Heat speed.
60/90/120/180
Cool Delay-To-Fan-On The period of time after a thermostat demand for cool before energizing
the circulator blower motor at Cool speed.
2
Cool Delay-To-Fan-Off* The period of time between the loss of a call for cool and the
deactivation of the blower motor at Cool speed.
2/45
Ignitor Warm-up The length of time allowed for the igniter to heat up prior to the initiation
of gas flow.
20
Auto Reset After one (1) hour of internal or external lockout, the control will auto-
matically reset itself and go into an auto restart purge for 60 seconds.
60 minutes
Humidifier Ye s
Electronic Air Cleaner Ye s
*This time will vary depending on option switch position. The control is factory set at 90 seconds HEAT
delay-to-fan-off and 45 seconds COOL delay-to-fan-off. See OPERATION section for further information
-40° to 175°F (-40° to 80°C)
HUMIDITY RANGE:
5% to 93% relative humidity (non-condensing)
MOUNTING:
Surface mount multipoise
Timing Specs: (@ 60 Hz**)
maximum
Flame Establishing Time: 0.8 sec
Flame Failure Response Time: 2.0 sec
**At 50 Hz, all timing specifications should be increased
by 20%
Gases Approved:Natural, Manufactured, Mixed, Liquified
Petroleum, and LP Gas Air Mixtures are all approved for use.

3
WARNING
!
FIRE HAZARD
• Do not exceed the specified voltage.
• Replace existing control with exact model and
dash number.
• Protect the control from direct contact with water
(dripping, spraying, rain, etc.).
• If the control has been in direct contact with water,
replace the control.
• Label all wires before disconnection when servic-
ing controls.Wiring errors can cause improper and
dangerous operation.
• Route and secure wiring away from flame.
SHOCK HAZARD
• Disconnect electric power before servicing.
• Ensure proper earth grounding of appliance.
• Ensure proper connection of line neutral and line
hot wires.
EXPLOSION HAZARD
• Shut off main gas to appliance until installation is
complete.
INSTALLATION
CAUTION
!
Do not short out terminals on gas valve or primary
control. Short or incorrect wiring may damage the
thermostat.
REPLACING 10M9301, 12L6901, 32M8801,
50A65-120, 50A65-121 or 56L8401
1. Disconnect all electrical power and shut off the gas
supply to the furnace.
2. Remove the access panel.
3. Disconnect wiring and remove existing ignition
control board from the control box.
4. Install provided circuit breaker in unit control box
or secure circuit breaker to a wire harness using
wire ties.
5. Position the provided mounting panel with the
arrow on the front of the panel pointing up. Position
the replacement 50A66-843 ignition control board
over the holes marked "A" in figure 1. Insert the
replacement control stand-off fasteners into the
holes in the mounting panel.
6. Insert the four provided stand-off fasteners into the
back of the mounting panel in the holes marked "B"
in figure 1. Insert the replacement control board
assembly into the existing holes in the control box
or blower panel.
7. Insert provided circuit breaker in series between the
blue transformer wire connecting position 3 on the
12-pin connector to the transformer (TH), optional 4"
blue wire provided for transformers that have a quick-
connect terminal.
8. Connect the remaining 120 VAC hot and neutral wires
and the flame sense wire to the replacement control
per table 1, page 4.
9. Affix wiring diagram 5001-6973 adjacent to the
existing unit wiring diagram.
10. Replace the access panel.
11. Restore the electrical power and gas supply. Refer
to the furnace installation instructions for start-up
and check-out procedures.
PROCEDURE 1
B B
B B
A A
A A
C
C
CC
Arrow on
front of pane
l
Figure 1 – Mounting Panel
Photo 1
MOUNTING PANEL
The Mounting Panel is required in Procedure 1 and Proce-
dure 2. It will become part of the installation for Procedure
1. It will be used as a template for locations to drill holes
in Procedure 2, Step 4A and 4B. It will become part of
the installation in Procedure 2, Step 4C.
Mounting panel
Circuit breaker
in series between
Pin 3 and
Transformer (TH)
Optional 4" blue
wire to connect to
Transformer (TH)

4
INSTALLATION
over the marks. Use the mounting panel
as a template to drill 3/16" holes through
each of the holes marked "A". Install the
replacement control in the freshly drilled holes
in the blower access panel.Use aluminum tape
to seal the unused holes.
B. When replacing original 63K8901 board in
downflow applications – Look at the existing
control board holes as if the unit were installed
in the upflow position. Make a mark 5/8"
ABOVE each of the existing mounting holes.
Position the provided mounting panel so that
the holes marked "C" in figure 1, page 3 are
over the marks. Use the mounting panel as a
template to drill 3/16" holes through each of
the holes marked "A". Install the replacement
control in the freshly drilled holes in the blower
access panel. Use aluminum tape to seal the
unused holes.
C. All other units – Position the provided
mounting panel so that the arrow on the
front of the panel is pointing up. Position the
replacement 50A66-843 ignition control board
over the holes marked "A" in figure 1, page 3.
Insert the replacement control stand-off
fasteners into the holes in the mounting panel.
80UHG, 90UGF, G23, G26, GHR26, G32,
GHR32, G40, G41, G50, G51, G60 and G61
units – Insert the four provided stand-off
fasteners into the back of the mounting panel in
the holes marked "B" in figure 1. 80MGF, G24M
and G27M units – Insert the four provided
stand-off fasteners into the back of the mounting
panel into the holes marked "C" in figure 1.
Insert the replacement control board assembly
into the existing holes in the control box or
blower panel.
5. Insert provided circuit breaker in series between
the blue wire on Pin 3 of the wiring harness (9-pin
to 12-pin) and the blue transformer wire. Optional
4" blue wire provided for transformers that have a
quick-connect terminal.
6. Connect the provided 9-pin to 12-pin wiring
harness to the unit 9-pin connector.
7. Connect the provided 4-pin to 6-pin wiring harness
to the unit 6-pin connector.
8. Connect the yellow wire from position 6 on the 12-
pin connector to the yellow transformer wire.
9. Connect GND wire to equipment ground.
10. Connect the remaining 120 VAC hot and neutral
wires and the flame sense wire to the replacement
control per table 2, page 5 .
11. Affix wiring diagram 5001-6972 adjacent to the
existing unit wiring diagram
12. Replace the access panel.
13. Restore the electrical power and gas supply. Refer
to the furnace installation instructions for start-up
and check-out procedures.
1. Disconnect all electrical power and shut off the gas
supply to the furnace.
2. Remove the access panel.
3. Disconnect wiring and remove existing ignition
control board from the control box.
4. A. When replacing original 63K8901 board
in upflow or horizontal applications or
downflow applications – Look at the existing
control board holes as if the unit were installed
in the upflow position. Make a mark 1" to the
right of each of the existing mounting holes.
Position the provided mounting panel so that
the holes marked "C" in figure 1, page 3 are
Optional 4" blue
wire to connect to
Transformer (TH)
Circuit breaker
in series between
Pin 3 and Trans-
former (TH)
Wiring harness
(4-pin to 6-pin)
Mounting panel
Wiring harness
(9-pin to 12-pin)
Transformer
GND
TABLE 1
Type Existing
Control Board
Replacement
Control Board
L1
120 VAC
COOL-H COOL
HEAT-H HEAT
PARK (2) PARK (2)
EAC-H EAC
LINE-H LINE
XFMR-H XFMR
HUM-H HUM
NONE FAN
Neutral
120 VAC
LINE-N
Neutral
120 VAC
(5)
HUM-N
EAC-N
XFMR-N
CIR-N
Flame Sense E33 FS
PROCEDURE 2
REPLACING 24L8501, 50A62-120, 50A62-121,
50A62-820, 56L8301, 63K8901 or 97L4801
Photo 2

5
OPERATION
OPTION SWITCHES
The option switches on the 50A66-843 control are used
to determine the length of the heat delay-to-fan-off and
cool-delay-to-fan-off periods. The following table shows
the time periods that will result from the various switch
positions.
HEAT delay-
to-fan-off:
Set switch
#1 #2
60 sec.
90 sec.*
120 sec.
180 sec.
Off Off
Off On
On Off
On On
COOL delay-
to-fan-off:
Set switch
#3
2 sec.
45 sec.*
*Factory Setting
Off
On
OPTION SWITCH POSITIONS
HEAT MODE
In a typical system, a call for heat is initiated by closing the
thermostat contacts. This starts the 50A66-843 control’s
heating sequence.The inducer blower and humidifier are
energized. After a 15-second pre-purge period, the 768A
Silicon Nitride ignitor is powered.
This controller has an adaptive algorithm that reduces
ignitor temperature to slightly greater than the minimum
temperature required to ignite gas in each particular
application. The control measures the line voltage and
determines an initial ignitor temperature setting based
on the measurement. After each successful ignition, the
control lowers the ignitor temperature slightly for the next
ignition attempt.The control continues to lower the ignitor
temperature until ignition does not occur, and the control
goes into retry mode. For the second attempt to ignite
gas within the same call for heat, the control increases
the ignitor temperature to the value it was on the third
previous successful ignition. After ignition is successful,
the control sets the ignition temperature at this value for
the next 255 calls for heat, after which the control repeats
the adaptive algorithm. The control is constantly making
adjustments to the ignitor temperature to compensate for
changes in the line voltage.
The 80 VAC Silicon Nitride ignitor manufactured by
White-Rodgers must be used. These ignitors are spe-
cially designed to operate with the 50A66-843's adap-
tive ignition routine to ensure the most efficient ignitor
temperature.
At the end of the ignitor warm-up time, both valves in the
gas valve are opened. Flame must be detected within 4
seconds.
If flame is detected, the delay-to-fan-on period begins.
After the delay-to-fan-on period ends, the circulator fan is
energized at heat speed. If there is an optional electronic
air cleaner on the system, the electronic air cleaner and
the humidifier are energized. When the thermostat is
satisfied, the gas valve is de-energized. After proof of
flame loss, the inducer blower remains energized to purge
the system for 5 seconds and the delay-to-fan-off period
begins. When the purge is complete, the inducer blower
and humidifier are de-energized.After the delay-to-fan-off
period ends, the circulator fan and electronic air cleaner
are de-energized.
If flame is not detected, both valves are de-energized,
the ignitor is turned off, and the 50A66-843 control goes
into the “retry” sequence.The “retry” sequence provides a
15-second wait following an unsuccessful ignition attempt
(flame not detected). After this wait, the ignition sequence
is restarted. If this ignition attempt is unsuccessful, three
more retries will be made before the control goes into
system lockout.
TABLE 2
Type Existing
Control Board
Replacement
Control Board
L1
120 VAC
ACB COOL COOL
ACB HEAT HEAT
PARK M1 PARK
PARK M2 PARK
ACC EAC
120 VAC HOT LINE
120 VAC TX XFMR
HTG ACC HUM
ACB LOW FAN
Neutral
120 VAC
Neutral 120 VAC
Return (5)
Neutral
120 VAC (5)
Flame Sense E33 FS
PROCEDURE 3
REPLACING 100925-01, 100925-02,
100925-03, 17W9201, 23W5101,
30W2501, 50A66-122, 50A66-123,
69M0801 or 69M1501
1. Disconnect all electric power and shut off gas
supply to the furnace.
2. Remove the access panel
3. Disconnect wiring and remove existing ignition
control board.
4. Insert the replacement board into existing holes.
5. Reconnect wiring.
6. Replace access panel.
7. Restore the electrical power and gas supply. Refer
to the furnace installation instructions for start-up
and check-out procedures.
INSTALLATION

6
OPERATION
SYSTEM LOCKOUT AND DIAGNOSTIC FEATURES
COOL MODE
In a typical system, a call for cool is initiated by closing
the thermostat contacts. This energizes the 50A66-843
control's cooling sequence.The compressor is energized
and the delay-to-fan-on period begins. After the delay-
to-fan-on periods ends, the circulator fan is energized at
cool speed. The electronic air cleaner (optional) is also
energized. After the thermostat is satisfied, the compres-
sor is de-energized and the delay-to-fan-off period begins.
After the delay-to-fan-off period ends, the circulator fan
and electronic air cleaner (optional) are de-energized.
MANUAL FAN ON MODE
If the thermostat fan switch is moved to the ON position,
the circulator fan (heat speed) and optional electronic air
cleaner are energized. When the fan switch is returned
to the AUTO position, the circulator fan and electronic air
cleaner (optional) are de-energized.
If flame is detected, then lost, the 50A66-843 control will
repeat the initial ignition sequence for a total of three
"recycles". After three unsuccessful "recycle" attempts,
the control will go into system lockout.
If flame is established for more than 10 seconds after igni-
tion, the 50A66-843 controller will clear the ignition attempt
(or retry) counter. If flame is lost after 10 seconds, it will
restart the ignition sequence.This can occur a maximum
of four times before system lockout.
A momentary loss of gas supply, flame blowout, or a
shorted or open condition in the flame probe circuit will be
sensed within 2 seconds. The gas valve will de-energize
and the control will restart the ignition sequence.Recycles
will begin and the burner will operate normally if the gas
supply returns, or the fault condition is corrected, before
the last ignition attempt. Otherwise, the control will go
into system lockout.
If the control has gone into system lockout, it may be pos-
sible to reset the control by a momentary power interrup-
tion of ten seconds or longer.Refer to PRECAUTIONARY,
SYSTEM LOCKOUT, AND DIAGNOSTIC FEATURES.
SYSTEM LOCKOUT FEATURES
When system lockout occurs, the gas valve is de-energized.
The circulator blower is energized at heat speed for some
faults, and if flame is sensed, the inducer blower is en-
ergized. The diagnostic indicator light will flash or glow
continuously to indicate system status. (System lockout
will never override the precautionary features.)
To reset the control after system lockout, do one of
the following:
1. Interrupt the call for heat at the thermostat for at least
one second, but less than 20 seconds (if flame is sensed
with the gas valve de-energized, interrupting the call
for heat at the thermostat will not reset the control).
2. Interrupt the 24 VAC power at the control for at least
ten seconds. You may also need to reset the flame
rollout sensor switch.
3. After one hour in lockout, the control will automatically
reset itself.
DIAGNOSTIC FEATURES
The 50A66-843 control continuously monitors its own
operation and the operation of the system. If a failure oc-
curs, the DS 1 (red) and DS 2 (green) LEDs will indicate
a failure code as shown on next page.

7
DIAGNOSTIC TABLE
DS 1 (Red) DS 2 (Green) Error/Condition Comments/Troubleshooting
Simultaneous
slow flash
Simultaneous slow
flash
Normal operation No fault
Simultaneous
fast flash
Simultaneous
fast flash
Normal operation with call
for heat
Normal operation
Slow flash On Open limit switch Verify continuity through rollout switch circuit
Off Slow flash Pressure switch stuck
closed/open
Pressure switch stuck closed. Check switch func-
tion, verify inducer is turning off.
Pressure switch stuck open. Check pressure switch
function and tubing. Verify inducer is turning on and
pulling sufficient vacuum to engage switch.
Alternate
slow flash
Alternate slow flash External lockout (retries) Failure to sense flame is often caused by carbon
deposits on the flame sensor, a disconnected or
shorted flame sensor lead or a poorly grounded
furnace. Carbon deposits can be cleaned with em-
ery cloth. Verify sensor is not contacting the burner
and is located in a good position to sense flame.
Check sensor lead for shorting and verify furnace
is grounded properly.
Slow flash Off Flame sensed with gas
valve de-energized
Verify the gas is operating and shutting down prop-
erly. Flame in burner assembly should extinguish
promptly at the end of the cycle. Check orifices and
gas pressure.
On Slow flash Open rollout switch Verify continuity through rollout switch circuit.
On On Module – internal fault
condition
Module contacts for gas valve not operating or
processor fault. Reset control, if condition persists,
replace module.
Slow flash Fast flash Low flame sense current Low flame sense current is often caused by carbon
deposits on the flame sensor, a poorly grounded
furnace or a mis-aligned flame sense probe.
Carbon deposits can be cleaned with emery cloth.
Check or improve furnace and module ground.
Verify sensor is located in or very near flame as
specified by the appliance manufacturer.
Fast flash Slow flash Grounding or reversed
polarity
Verify the control and furnace are properly ground-
ed. Check and reverse polarity (primary) if incorrect.
Alternate fast
flash
Alternate fast flash Module ignitor contact
failure
Fault code indicates the module ignitor contacts
are not functioning properly. Replace module.
TROUBLESHOOTING

White-Rodgers is a business
of Emerson Electric Co.
The Emerson logo is a
trademark and service mark
of Emerson Electric Co.
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