Emerson Climate Technologies
Emerson Climate Technologies WHITE-RODGERS 21M51U-843 Integrated Furnace Control
Hot-surface ignition furnace control with two retries, 90-second ignition cycle and 1.5 A main-valve output
- Controls hot-surface ignition with two retries for reliable starts
- Operates from -40 °F to 175 °F for extreme environments
- Pre-purge and post-purge cycles of 15 seconds clear the chamber
- Automatic reset after one hour restores operation without a service call
- Compatible with Goodman, Lennox, Trane and White-Rodgers furnaces
Furnace control for HSI systems
The WHITE-RODGERS 21M51U-843 is an integrated furnace control designed for hot surface ignition applications. It manages the ignition sequence with a 15 second pre-purge and a 90 second ignition cycle. The board operates across a -40 to 175 degrees F temperature range. It is intended as a replacement component for compatible heating equipment.
Suits Goodman, Lennox, Trane repairs
This control fits systems from Goodman, Lennox, Trane and White-Rodgers brands requiring a two-retry ignition logic. It provides a 1.5 A main valve output and a 0.3 uA flame sensor current. Technicians needing a different retry count, lockout timing or valve current rating should verify their equipment specifications before selecting this board.
Two-retry ignition logic
The defining specification is the number of retries set at 2 before the control enters a 5 minute lockout. An automatic reset occurs after 1 hour if the fault clears. Matching this retry behaviour to the original furnace requirement determines whether this is the correct replacement part.
Highlights
- Controls hot-surface ignition with two retries for reliable starts
- Operates from -40 °F to 175 °F for extreme environments
- Pre-purge and post-purge cycles of 15 seconds clear the chamber
- Automatic reset after one hour restores operation without a service call
- Compatible with Goodman, Lennox, Trane and White-Rodgers furnaces
Specifications
| Brand | WHITE-RODGERS |
|---|
Questions about this item
Does the 21M51U-843 require a hot-surface ignitor and flame sensor rated for 0.3 uA to operate?
Yes, this control is designed for hot-surface ignition systems and supplies a flame sensor current output of 0.3 uA, so compatible ignitor and sensor components are required.
Will the 21M51U-843 work with my existing Goodman, Lennox, Trane or White-Rodgers furnace?
The control lists compatibility with Goodman, Lennox, Trane and White-Rodgers brands, making it a direct replacement for many models from those manufacturers.
How can I verify the 21M51U-843 is functioning correctly after installation?
After power-up, the control runs a 15-second pre-purge, followed by a 90-second HSI ignition trial and a 15-second post-purge; successful flame detection and steady main valve output of 1.5 A indicate normal operation.
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