White-Rodgers 21M51U-843 universal integrated furnace control fits 2-stage systems with PSC circulator output. It provides two-speed inducer output and two-stage gas valve output.
The board includes the 21D64-2 silicon nitride ignitor kit and module. A tri-color LED shows furnace status, and pushbutton retrieval reads fault history.
21M51U-843 Highlights
Universal 2-stage operation
Drives 3-speed PSC circulator, 2-speed inducer and 2-stage gas valve.
Pushbutton fault history
Recalls stored faults without extra tools for faster service.
Tri-color status LED
Green, red and amber signals show furnace status at a glance.
21D64-2 ignitor kit included
Comes with silicon nitride ignitor kit and module in the box.
21M51U-843 Specifications
Fan timing: Heat fan off delay dipswitch selectable, fan on delay for cooling, auto second-stage delay
In the box: 21D64-2 silicon nitride ignitor kit and module
System type: 2-stage gas furnace with PSC circulator
Inducer output: Two-speed
Gas valve output: Two-stage
Status indicator: Tri-color LED (green, red, amber)
