White-Rodgers™ 21M51U-843

The 50M51-843 is a universal replacement control for two stage automatic gas ignition controls employing a microprocessor to continually monitor, analyze, and control the proper operation of the gas burner and inducer. the 50M51-843 controls a multiple tapped induction circulation 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. the 50M51-843 quickly and easily replaces white Rodgers 50M51-XXX controls.

White-Rodgers™ Hot Surface Ignition Control, Universal, 15-1/2 in Lead Length, 15-1/2 in Probe Length, 25 VAC, 530 mA, 1/4 in Spade Terminal and Molex Plug, Natural Gas/Liquid Propane, 17 sec Igniter Warm-Up Time, 5-1/4 in Width, 1-1/4 in Depth, 8 in Height, Import

• 120 VAC 3 speed PSC circulator output, two-speed inducer output, two stage gas valve output
• Pushbutton fault history retrieval
• Furnace status LED - tri-color (green, red and amber)
• Heat fan off delay (dipswitch selectable), fan on delay for cooling
• Auto second stage delay (dipswitch selectable)
• -40 to 175 deg F
• 2-stage gas valve output
• 3 A fuse protection
• Pressure switch inputs and monitoring
• Flash microprocessor with non-volatile memory
• Flame current measurement points
• 1.5 A valve relay
• 2.2 FLA to 3.5 LRA inducer relay
• 14.5 FLA to 25 LRA circulator relay
• 1 a max at 120 VAC humidity
• 1 a max at 120 VAC electronic air cleaning
• 4 a max at 132 VAC ignitor relay
• 0.3 uA DC max current for flame detection
• 0.1 uA DC min current for flame detection
• 100 M ohm leakage resistance, 3 speed PSC blower motor systems
• Two stage hot surface ignition control

• Catalog https://www.capitolgroupinc.com//ASSETS/DOCUMENTS/ITEMS/EN/White_Rodgers_21M51U-843_Catalog.pdf