50M56U-843
Universal Single Stage
HSI Integrated Furnace Control Kit
INSTALLATION INSTRUCTIONS
FAILURETOREADANDFOLLOWALLINSTRUCTIONS
CAREFULLY BEFORE INSTALLING OR OPERATING
THIS CONTROL COULD CAUSE PERSONAL INJURY
AND/OR PROPERTY DAMAGE.
INSTALLER MUST READ
PAGE 3 CONTAINS WIRING HARNESS AND
BLOWER CONNECTION INSTRUCTIONS FOR
ALL APPLICATIONS AND IMPORTANT OEM
REPLACEMENT INSTRUCTION FOR:
● TRANE / AMERICAN STANDARD
● RHEEM / RUUD
● BRYANT / CARRIER / DAY & NIGHT / PAYNE
DESCRIPTION
The 50M56U-843 kit is a Universal Single Stage HSI Integrated
Furnace Control that employs a microprocessor to continually
monitor, analyze, and control the proper operation of the gas
burner, inducer, and fan.
The kit contains:
• 50M56-843 Ignition Control Module
• 21D64-2 Ignitor Kit
21D64-2
50M56-843
• Set of Interconnect Harnesses
PRECAUTIONS
Installation should be done by a qualified heating and air
conditioning contractor or licensed electrician.
WARNING
!
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.
Failure to comply with the following warnings could result
in personal injury or property damage.
Do not exceed the specification ratings.
FIRE HAZARD
All wiring must conform to local and national electrical codes
and ordinances.
• 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.).
This control is a precision instrument, and should be handled
carefully. Rough handling or distorting components could
cause the control to malfunction.
Following installation or replacement, follow manufacturer’s
recommended installation/service instructions to ensure
proper operation.
• 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.
CAUTION
!
Do not short out terminals on gas valve or primary
control. Short or incorrect wiring may damage the
thermostat.
SHOCK HAZARD
• Disconnect electric power before servicing.
• Ensure proper earth grounding of appliance.
• Ensure proper connection of line neutral and line
hot wires.
CONTENTS
Description................................................................... 1
Precautions.................................................................. 1
Specifications .............................................................. 2
Installation ................................................................... 2
Mounting & Wiring
EXPLOSION HAZARD
• Shut off main gas to appliance until installation
is complete.
Operation..................................................................... 6
Troubleshooting ........................................................... 8
PART NO. 37-7042C
Replaces 37-7042B
1103
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INSTALLATION
INSTALLER MUST READ FOR PROPER
INSTALLATION
• Wiring harnesses and a Universal 21D64-2 ignitor are
included in this package. Refer to the enclosed “Cross
Reference and Harness Application Chart” (Part Number
37-7077) for harness selection and ignitor application
information. Ignitor installation instructions are in the
UNIVERSAL 21D64-2 Ignitor package included with this kit.
• IMPORTANT: For continuous fan speed operation, one of
the unused parked motor taps must be connected to the
low heat speed terminal. Failure to do this will result in the
blower not energizing in the constant fan mode operation.
Refer to figure 1.
Figure 1
For continuous fan speed
connect one of the unused
parked terminals here
• Installer must read Page (6) “Operation” and follow option
switch setting for proper control operation.
• In certain applications it may be necessary to remove the
control board from the cover to be mounted in the space
allowed. Standoffs supplied in the package must be
installed before the control board can be mounted.
• 4 Blower lead extensions are included in the kit if extra
length is needed to complete installation.
Pin 11 (RO In)
IMPORTANT OEM REPLACEMENT INSTRUCTIONS
Jumper 0151-290600
(for Trane and American
Standard applications only)
• TRANE and AMERICAN STANDARD
For all TRANE and AMERICAN STANDARD furnaces
only: Install jumper 0151 290600 (included in this
package) into the back of the furnace 12 pin connector
harness from pin 5 to pin 11 as shown in Figure 2.
Make sure jumper snaps into the connector securely.
• RHEEM / RUUD (1994 and earlier models)
If the furnace control being replaced has 2 green lights
and NO amber light (furnace date code 3294 or earlier)
a Flame Sensor Kit, RHEEM Part Number 62-24044-71
(not available from White-Rodgers) is required. Install
the flame sensor and plug the flame sensor lead into
pin 7 of the connector on the furnace as detailed in the
Rheem Flame Sensor Kit instructions. Plug the furnace
connector into harness “B” (included in this package).
Plug the other end of harness “B” into the new module.
Attach the orange wire from harness “B” (3/16” female
spade terminal) to FS on the new module to complete
the flame sense circuit.
Pin 5 (RO Out)
Figure 2. 12 Pin Connector (back view)
on existing Wire Harness in Furnace
• BRYANT / CARRIER / DAY & NIGHT / PAYNE
This kit will not replace BRYANT / CARRIER / DAY &
NIGHT / PAYNE HK42FZ013 modules or CARRIER
/ BDP modules using an 11 pin (straight) connector.
Refer to the enclosed “Cross Reference and Harness
Application Chart” (Instruction sheet Part Number 37-
7077) included with this kit for the list of modules it
replaces.
3
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WIRING DIAGRAM
TYPICAL SYSTEM WIRING DIAGRAM
HOT
(LINE)
NEUTRAL
(LINE)
120 VAC
24 VAC CLASS II
TRANSFORMER
TH
24 VAC
50M56
TR
COOL
LO HEAT
HI HEAT
LINE
CIRCULATOR
BLOWER
XFMR
EAC
HUM
PARK
PARK
INDUCER
IGNITOR
IND-N
IND
IGN
HUMIDIFIER
IGN-N
[4-Pin Connector]
CIR N
LINE N
XFMR N
HUM N
EAC N
ELECTRONIC
AIR CLEANER
Y
W
G
R
Y
W
G
R
COMPRESSOR
CONTACTOR
THERMOSTAT
C
FLAME
SENSOR
PROBE
FS
PRESSURE SWITCH (N. O.)
PSI
PSO
HLI
HLO
RO OUT
GND
RO IN
MV LO
MV HI
MV COM
TR
HIGH LIMIT
(N. C.)
AUX. HIGH
LIMIT (N. C.)
ROLLOUT
(N. C.)
2 STAGE
GAS
1 STAGE
GAS
VALVE
VALVE
TH
[12-Pin Connector]
For Goodman 50M56-289 Application
LEGEND
PSO
HLI
PSI
HLO
Low Voltage (24 VAC)
Line Voltage (120 VAC)
MV
LO
RO
OUT
RO
IN
GND
MV
HI
MV
COM
IND
N
IGN
N
TR
IND
TH
IGN
N. C. = Normally closed switch
N. O. = Normally open switch
4-Pin Connector
12-Pin Connector
4
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WIRING DIAGRAM
TYPICAL SYSTEM WIRING TABLE
50M56
TERMINAL
SYSTEM COMPONENT
TERMINAL
TYPE
CONNECTION
low voltage thermostat W terminal (or equivalent)
low voltage thermostat G terminal (or equivalent)
low voltage thermostat R terminal (or equivalent)
low voltage thermostat Y terminal (or equivalent)
(2nd wire from Y terminal goes to 24 VAC HOT side of
compressor contactor coil)
W
G
R
Y
Terminal
block with
captive
screws
24 VAC COMMON side of compressor contactor coil
high limit OUTPUT
C
HLO (Pin 1)
MV LO (Pin 2)
TH (Pin 3)
gas valve first stage
24 VAC transformer (low voltage HIGH side)
pressure switch OUTPUT
PSO (Pin 4)
RO OUT (Pin 5)
TR (Pin 6)
rollout switch OUTPUT
PSO
HLI
PSI
HLO
24 VAC transformer (low voltage COMMON side)
high limit INPUT
MV
LO
RO
OUT
RO
IN
GND
HLI (Pin 7)
GND (Pin 8)
MV COM (Pin 9)
PSI (Pin 10)
RO IN (Pin 11)
MV HI (Pin 12)
IND (Pin 1)
IGN (Pin 2)
IND-N (Pin 3)
IGN-N (Pin 4)
COOL
MUST BE RELIABLY GROUNDED TO CHASSIS
gas valve COMMON
MV
HI
MV
COM
TR
TH
pressure switch INPUT
rollout switch INPUT
gas valve second stage
inducer HOT side
ignitor HOT side
IND
N
IGN
N
IND
IGN
inducer NEUTRAL side
ignitor NEUTRAL side
circulator blower COOL SPEED terminal
circulator blower LO HEAT SPEED terminal
circulator blower HI HEAT SPEED terminal
unused terminals
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
spade terminal
LO HEAT
HI HEAT
PARK (2 terminals)
LINE
input voltage (120 VAC) HOT side
24 VAC transformer line voltage HOT side
electronic air cleaner HOT side
humidifier HOT side
XFMR
EAC (optional)
HUM (optional)
CIR N
circulator blower NEUTRAL terminal
input voltage (120 VAC) NEUTRAL side
24 VAC transformer line voltage NEUTRAL side
electronic air cleaner NEUTRAL side
humidifier NEUTRAL side
LINE N
XFMR N
EAC N (optional)
HUM N (optional)
FS
flame sensor probe†
† Maximum recommended flame probe wire length is 36 inches.
5
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OPERATION
If flame is not detected, both valves are de-energized, the
ignitor is turned off, and the 50M56U-843 control goes into the
“retry” sequence. The “retry” sequence provides a 60-second
wait following an unsuccessful ignition attempt (flame not
detected). After this wait, the ignition sequence is restarted
with an additional 1 second of ignitor warm-up time.
OPTION SWITCHES
The option switches on the 50M56U-843 control are used
to determine the length of the heat delay-to-fan-off period,
the mode of operation, and the 2nd stage delay period. The
following illustration shows the options and the selections of
the switch positions. The switches are shown in the factory
default positions.
If flame is established for more than 10 seconds after ignition,
the 50M56U-843 controller will clear the ignition attempt (or
retry) counter. If flame is lost after 10 seconds, it will re-cycle
the ignition sequence.
*
*
During burner operation, a momentary loss of power of 50
milliseconds or longer will de-energize the main gas valve.
When power is restored, the gas valve will remain de-energized
and a restart of the ignition sequence will begin immediately.
*MODE and 2ND STG DLY for Goodman 50M56-289 only
HEAT MODE
When heat is required, the thermostat will send a call for heat
to the control. This starts the control’s heating sequence. The
ignitor and humidifier (optional) are powered. The ignitor is
powered after the pre-purge period.
A momentary loss of gas supply, flame blowout, or a shorted or
open condition in the flame probe circuit will be sensed within
2.0 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.
Upon initial application of power, the ignitor warm-up time is 17
seconds. The ignitor on-time will then be increased depending
on whether or not flame is achieved. The warm-up time is
limited to a maximum of 19 seconds. During the first 64 warm-
up periods following power-up, the warm-up time may not be
less than 17 seconds.
If the control has gone into system lockout, it may be possible
to reset the control by a momentary power interruption of one
second or longer. Refer to SYSTEM LOCKOUT FEATURES.
COOL MODE
In the event of a retry, the warm-up time will be increased by
one second and locked in at that duration. Once the warm-up
time is locked, it remains fixed until another call for heat results
in a retry, in which case the warm-up time is again increased
by one second and remains locked.
In a typical system, a call for cool is initiated by closing the
thermostat contacts. This energizes the 50M56U-843 control
and the compressor. The cool delay-to-fan-on period begins.
After the delay period ends, the optional electronic air cleaner
is energized, and the circulator fan is energized at cool
speed. After the thermostat is satisfied, the compressor is de-
energized and the cool mode 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.
In the event of two successive retry attempts, the warm-up
time will be unlocked and set to 19 seconds. If flame is then
achieved, the warm-up time will begin adapting again with the
next call for heat. If, however, this third attempt fails to achieve
flame, the control will go into system lockout.
After the ignitor warm-up period, MV LO (first stage) and MV
HI (second stage) are both energized to the gas valve. Flame
must be detected within 4 seconds. If flame is detected, the
30-second HEAT delay-to-fan-on period begins. The circulator
and electronic air cleaner (optional) will also energize at this
time.
MANUAL FAN ON MODE
If the thermostat fan switch is moved to the ON position, the
circulator fan (low 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.
1 Stage operation – If the Option Switch MODE (SW1-2) is
set to the 1 STG position, both MV LO and MV HI will remain
energized.
SYSTEM LOCKOUT AND
DIAGNOSTIC FEATURES
2 Stage operation (Goodman 50M56-289 Application only)
– If the Option Switch MODE is set to 2 STG, MV HI will de-
energize after 5 seconds, leaving MV LO energized. If the
MODE is in the 2 STG position, 2nd STG DLY (SW1-3) will
determine the second stage- on delay as follows:
5 MIN – On call for heat, the 5 minute 2nd stage recognition
timer begins. After the 5-minute delay, the second stage heat
(MV HI) is energized.
SYSTEM LOCKOUT FEATURES
When system lockout occurs, the gas valve is de-energized,
the circulator blower is energized at heat speed, and, if flame
is sensed, the inducer blower is energized. The diagnostic
indicator light will flash or glow continuously to indicate
system status. (System lockout will never override the
precautionary features.)
AUTO – On call for heat, the automatic second stage will
determine the optimum timing between stages for comfort.
Auto will adapt the delay to energize MV HI from instantly to
up to 12 minutes.
To reset the control after system lockout, do one of the
following:
1. Interrupt the call for heat or cool 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 one
second. You may also need to reset the flame rollout
sensor switch.
When the thermostat is satisfied, the gas valve is de-energized.
After proof of flame loss, the heat delay-to-fan-off period begins
and the inducer blower remains energized to purge the system
for 25 seconds.When the purge is complete, the inducer blower
is de-energized. After the delay-to-fan-off period ends, the
circulator fan and electronic air cleaner are de-energized.
3. After one hour in lockout, the control will automatically
reset itself.
6
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OPERATION
DIAGNOSTIC FEATURES
FAULT CODE RESET
The 50M56U-843 control continuously monitors its own
operation and the operation of the system. If a failure occurs,
the LED will indicate a failure code as shown on page 8. If
the failure is internal to the control, the LED will stay off
or flash 8 times. In this case, the entire control should be
replaced, as the control is not field-repairable.
The stored fault codes can be erased from memory. When
the control is in standby mode (no call for heat or cool), press
the FAULT RECALL switch for five to ten seconds or until
the diagnostic LED begins to rapid flash. When the switch is
released, the LED will turn off for two seconds to indicate the
codes are erased. After two seconds the LED will turn on to
indicate return to normal status. If the switch is held pressed
for over ten seconds the rapid flash will stop and the LED will
be on to indicate return to normal status.
Failure codes will flash the LED in the following flash-
pause sequences to indicate failure status (each flash will
last approximately 0.25 seconds, and each pause will last
approximately 2 seconds).
FAULT RECALL
The 50M56U-843 has only one serviceable part –an automotive
type fuse, which protects the low voltage transformer from
damage if the output is short-circuited. If the fuse has opened
up, remove whatever caused the short circuit and replace
the fuse with only a 3 Amp automotive type fuse. If the fuse
does not correct the condition, replace the entire 50M56U-843
control. There are no other user serviceable parts.
The last five fault codes stored can be displayed on the
diagnostic LED. When the control is in standby mode (no
call for heat or cool), press the FAULT RECALL switch for
approximately two seconds or until the diagnostic LED turns
off. Release the switch and the LED will remain off for two
seconds. Then the fault codes will display beginning with the
most recent fault first with a two second pause between codes.
After the stored fault codes have all displayed, the LED will
remain off for two seconds and then turn on to indicate return
to normal status. While displaying the stored fault codes, the
control will ignore any new call for heat, cool or fan.
DEFINITION OF TERMS
Inter-purge – 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.
Auto Restart – After one (1) hour of internal or external
lockout, the control will automatically reset itself and go
into an auto restart purge for 60 seconds.
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.
Post-purge Time – 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.
CoolDelay-To-Fan-On–Theperiodoftimeafterathermostat
demand for cool before energizing the circulator blower
motor at Cool speed.
Pre-purgeTime – 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.
Flame Failure Response Time (FFRT) – The period of time
between loss of the supervised main burner flame and
the action to shut off the gas supply.
Recycles – The additional attempts within the same
thermostat cycle for ignition after loss of the supervised
ignition source or the supervised main burner flame.
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.
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.
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.
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.
Igniter Warm-up Time – The length of time allowed for the
igniter to heat up prior to the initiation of gas flow.
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.
7
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TROUBLESHOOTING
Red LED
Flash
Error/Condition
Comments/Troubleshooting
1
External lockout (exceeded 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 emery 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. Verify
gas supply to valve, gas valve in "On" position and appliance
lighting properly. Verify flame reaches flame sensor during
ignition attempts and gas pressures are correct.
2
Pressure switch stuck closed
Pressure switch stuck open
Pressure switch stuck closed. Check switch function, verify
inducer is turning off. Refer to wiring diagram, terminals PSI /
PSO.
3
Check pressure switch function and tubing. Verify inducer is
turning on and pulling sufficient vacuum to engage switch.
Refer to wiring diagram, terminals PSI / PSO.
4
5
Open high temperature limit switch
Verify continuity through limit switch circuit. Refer to wiring
diagram terminals, HLI / HLO.
Flame sensed with gas valve de-energized Verify the gas valve is operating and shutting down properly.
Flame in burner assembly should extinguish promptly at the
end of the cycle. Check orifices and gas pressure.
6
7
Open rollout switch
Verify continuity through rollout switch circuit. Refer to wiring
diagram terminals, RO IN / RO OUT.
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. Refer to wiring diagram FS
terminal and GND.
8
Ignitor relay fault
This flash code does not indicate a broken, disconnected or
shorted ignitor. It indicates the ignitor relay contacts on the
ignition module are not functioning properly. Replace the
ignition module.
Rapid Flash Reversed polarity
Verify the control and furnace are properly grounded. Check
and reverse polarity (primary or secondary) if incorrect.
Continuous
On
Normal operation
Control failure
No fault
Off
Verify power to the control, replace control if power is at the
control and no lit Red LED
White-Rodgers is a division
of Emerson Electric Co.
The Emerson logo is a
trademark and service mark
of Emerson Electric Co.
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