White Rodgers Thermostat 50M56U 843 User Manual

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  
 
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
 
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
 
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
 
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, ame 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
 
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-OnTheperiodoftimeafterathermostat  
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
 
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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