21V51U-843
Integrated Two-Stage/Variable Speed Motor
Hot Surface Ignition Control Kit
INSTALLATION INSTRUCTIONS
Operator: Save these instructions for future use!
FAILURE TO READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY BEFORE
INSTALLING OR OPERATING THIS CONTROL COULD CAUSE PERSONAL
INJURY AND/OR PROPERTY DAMAGE.
PRECAUTIONS
CONTENTS
Description ....................................................................... 1
Precautions ...................................................................... 1
Specifications ...................................................................2
Timing Table & Definitions ................................................2
Installation ........................................................................3
Mounting & Wiring
Option Switch Settings .....................................................4
Mounting Hole Template ..................................................5
Wiring ..............................................................................6
Operation .........................................................................8
Troubleshooting ................................................................8
DESCRIPTION
The kit Includes:
• 50V51-843 Ignition Control Module
• 21D64-2 Ignitor Kit
• Set of Interconnect Harnesses (for Goodman)
The 50V51-843 is a two-stage automatic gas interrupted ignition
control employing a microprocessor to continually monitor,
analyze, and control the proper operation of the gas burner and
inducer. The 50V51-843 provides signals for proper operation
of a variable fan speed circulator blower.
Signals interpreted during continual surveillance of the two-
stage thermostat and flame sensing element initiate automatic
ignition of the burner, sensing of the flame, and system shutoff
during normal operation.
The control incorporates system fault analysis for quick gas
flow shutoff, coupled with automatic ignition retry upon sensing
a fault correction.
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 components 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.
• 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 installation is
complete.
Do not short out terminals on gas valve or primary
control. Short or incorrect wiring may damage the
thermostat.
white-rodgers.com
emersonclimate.com
PART NO. 37-7115D
Replaces 37-7115C
1617
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