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White Rodgers 50M56U-843 - User Manual

White Rodgers 50M56U-843
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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
INSTALLER MUST READ
www.white-rodgers.com
www.emersonclimate.com
50M56U-843
Universal Single Stage
HSI Integrated Furnace Control Kit
INSTALLATION INSTRUCTIONS
FAILURE TO READ AND FOLLOW ALL INSTRUCTIONS
CAREFULLY BEFORE INSTALLING OR OPERATING
THIS CONTROL COULD CAUSE PERSONAL INJURY
AND/OR PROPERTY DAMAGE.
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
• SetofInterconnectHarnesses
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specication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 components could
cause the control to malfunction.
Following installation or replacement, follow manufacturer’s
recommended installation/service instructions to ensure
proper operation.
PRECAUTIONS
PART NO. 37-7042C
Replaces37-7042B
1103
Do not short out terminals on gas valve or primary
control. Short or incorrect wiring may damage the
thermostat.
CAUTION
!
Failure to comply with the following warnings could result
in personal injury or property damage.
FIRE HAZARD
• Donotexceedthespecied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ame.
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.
WARNING
!
CONTENTS
Description ...................................................................1
Precautions ..................................................................1
Specifications ..............................................................2
Installation ...................................................................2
Mounting & Wiring
Operation ..................................................................... 6
Troubleshooting ........................................................... 8
50M56-843
21D64-2

Table of Contents

Questions and Answers

  • D
    david42Aug 14, 2025
    How to fix external lockout on White Rodgers Control Unit?
    • M
      Megan WebbAug 14, 2025
      If the White Rodgers Control Unit experiences an external lockout due to exceeded retries, it's often because the flame sensor isn't detecting the flame properly. This can be due to carbon deposits on the flame sensor. Clean these deposits off with emery cloth. Ensure the sensor isn't touching the burner and is correctly positioned to sense the flame. Also, check the sensor lead for any shorts and make sure the furnace is properly grounded. Confirm gas supply to the valve, the gas valve is in the 'On' position and the appliance is lighting correctly. Check that the flame reaches the flame sensor during ignition attempts and that gas pressures are correct.
  • K
    Kristin JensenAug 18, 2025
    Why is the flame sense current low on my White Rodgers 50M56U-843?
    • D
      Debbie WernerAug 18, 2025
      A low flame sense current in your White Rodgers Control Unit is often due to carbon deposits on the flame sensor. You can clean these deposits using emery cloth. Other potential causes include a poorly grounded furnace, which you should check and improve the grounding, or a misaligned flame sense probe. Ensure the sensor is located in or very near the flame as specified by the appliance manufacturer. Refer to wiring diagram FS terminal and GND.
  • J
    Jeremy HansenAug 21, 2025
    What to do if flame is sensed with gas valve de-energized in White Rodgers 50M56U-843?
    • N
      Nicholas BryantAug 21, 2025
      If the White Rodgers Control Unit senses a flame even when the gas valve is de-energized, verify that the gas valve is operating and shutting down properly. The flame in the burner assembly should extinguish promptly at the end of the cycle. Also, check the orifices and gas pressure.
  • K
    Kimberly KingAug 25, 2025
    How to check reversed polarity on White Rodgers Control Unit?
    • E
      Emily LarsenAug 25, 2025
      To address reversed polarity on the White Rodgers Control Unit, verify that the control and furnace are properly grounded. Check the polarity and reverse it (either primary or secondary) if it's incorrect.
  • E
    Ellen LewisAug 27, 2025
    What to do if pressure switch stuck open in White Rodgers Control Unit?
    • L
      Lauren CollinsAug 27, 2025
      Check the pressure switch function and tubing. Verify the inducer is turning on and pulling sufficient vacuum to engage the switch. Refer to wiring diagram, terminals PSI / PSO.
  • R
    Ricky RobinsonAug 31, 2025
    What to do if pressure switch stuck closed in White Rodgers Control Unit?
    • S
      Steve DiazAug 31, 2025
      Check switch function, verify inducer is turning off. Refer to wiring diagram, terminals PSI / PSO.
  • C
    Carlos MillerSep 3, 2025
    How to check open high temperature limit switch on White Rodgers 50M56U-843 Control Unit?
    • M
      Mariah ReynoldsSep 3, 2025
      Verify continuity through limit switch circuit. Refer to wiring diagram terminals, HLI / HLO.
  • D
    Dawn RodriguezSep 6, 2025
    How to check open rollout switch on White Rodgers 50M56U-843 Control Unit?
    • T
      Timothy BrownSep 7, 2025
      Verify continuity through rollout switch circuit. Refer to wiring diagram terminals, RO IN / RO OUT.
  • M
    Mr. Terry FowlerSep 10, 2025
    How to fix ignitor relay fault on White Rodgers 50M56U-843?
    • F
      fchristensenSep 10, 2025
      Replace the ignition module.

Summary

Installer Must Read

Product Overview and Precautions

Description

Details the control's function, components, and kit contents.

Precautions

Essential safety warnings for installation and operation to prevent injury or damage.

Specifications

Installation

Mounting and Wiring

Details mounting procedures and wiring requirements for the control.

Important OEM Replacement Instructions

Specific instructions for replacing controls in certain OEM furnace models.

Wiring Diagrams

Typical System Wiring Diagram

Illustrates the typical system wiring connections for the control.

Typical System Wiring Table

Lists terminals and their corresponding system component connections.

Operation

Option Switches

Explains how option switches determine control operation modes and delays.

Heat Mode

Describes the heating sequence, ignitor operation, and fan control.

Cool Mode

Explains the cooling sequence, including compressor and fan control.

System Lockout and Diagnostic Features

Covers system lockout conditions and how to reset the control.

Diagnostic Features

Fault Code Reset

Instructions for clearing stored fault codes from the control's memory.

Fault Recall

How to display previously stored failure codes using the diagnostic LED.

Definition of Terms

Glossary of terms used in the operation and troubleshooting sections.

Troubleshooting

Red LED Flash Codes

Lists error conditions indicated by red LED flash codes.

Rapid Flash

Indicates reversed polarity error.

Continuous On

Indicates normal operation status.

Off

Indicates a control failure.

White Rodgers 50M56U-843 Specifications

General IconGeneral
TypeIntegrated Furnace Control
Voltage24 VAC
Ignition TypeHot Surface Ignition
Replaces50M56-843, 50M56U-843
Compatible Furnace TypesSingle stage
Safety Featurespressure switch monitoring
Operating Temperature Range-40°F to 176°F (-40°C to 80°C)

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