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Green rectangular circuit board with black components and white text

WHITE RODGERS (EMERSON ELEC)

WHITE RODGERS 50A55-3797 Furnace Board 120V HSI control

SKU CH-DBY0-EQFP4

120V hot-surface ignition board for Trane single-stage furnaces with humidifier, air-cleaner and two-speed circulator outputs plus selectable fan-off delay

  • Direct 120 V hot-surface ignition for reliable furnace starts
  • 120 V humidifier and air-cleaner outputs simplify accessory wiring
  • 5 FLA / 25.0 LRA circulator relay handles two-speed PSC motors
  • 5 A fuse protection guards the control against over-current faults
  • Replaces multiple Trane and White-Rodgers part numbers for easy service

White Rodgers 50A55-3797 Furnace Board

This 120 V hot-surface-ignition control board replaces Trane part numbers CNT02789, CNT02891, CNT03799 and White Rodgers 50A55-474, 50A55-476 and 50A55-571. It operates from a 25 VAC 50/60 Hz supply drawing 0.45 A and provides integrated furnace control for single-stage systems.

Electrical Ratings and Interface Limits

The valve relay is rated at 1.5 A at 25 VAC while the ignitor relay handles 6.0 A at 120 VAC resistive. The inducer relay manages 2.2 FLA and 3.5 LRA at 120 VAC and the circulator relay 14.5 FLA and 25.0 LRA at 120 VAC. Flame detection requires a minimum 1 µA DC current with non-detection below 0.1 µA and maximum leakage resistance of 100 M ohms.

Capacity and Operational Headroom

The board supplies 120 VAC outputs for ignitor, humidifier, electronic air cleaner and two-speed PSC circulator with 5 A fuse protection. It operates across a -40 °F to 175 °F temperature range and includes selectable heat fan off-delay via dipswitch. Installations requiring multi-stage gas control or modulating gas valve outputs are not supported by this single-stage design.

Highlights

  • Direct 120 V hot-surface ignition for reliable furnace starts
  • 120 V humidifier and air-cleaner outputs simplify accessory wiring
  • 5 FLA / 25.0 LRA circulator relay handles two-speed PSC motors
  • 5 A fuse protection guards the control against over-current faults
  • Replaces multiple Trane and White-Rodgers part numbers for easy service

Specifications

BrandWHITE-RODGERS

Questions about this item

Which White Rodgers replacement part numbers does the 50A55-3797 board cover?

It replaces White Rodgers 50A55-474, 50A55-476 and 50A55-571, plus Trane CNT02789, CNT02891, CNT03799, CNT2789, CNT2891, CNT3799, D341122P01, D341235P01 and D341235P03.

What does the 6.0 amp ignitor relay rating mean when the board is installed?

The ignitor relay can switch up to 6.0 amp resistive load at 120 VAC, so it will drive a standard hot-surface ignitor without exceeding its contact rating.

How does the 25 VAC input voltage limit what the board can do?

The control logic runs on 25 VAC at 0.45 amp maximum, while all high-voltage outputs (ignitor, humidifier, air cleaner, circulator) are switched at 120 VAC through separate relays.

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