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Emerson Climate Technologies

Emerson Climate Technologies WHITE-RODGERS 21M51U-843 Integrated Furnace Control

SKU CH-E523-GA290

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.

How it compares

Measured against everything we stock in Industrial Heating Equipment, at today’s prices. Recalculated every night.

Price $198.99
Pricier than about 73% of the 24 comparable items (median $78.49).

Specifications

Product
Brand nameWHITE-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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