21M51U-843

The 21M51U-843 from White Rodgers is a universal two-stage HSI integrated 3-speed (PSC) circulator furnace control kit. 21M51U-843 simplifies stocking, installation and ensures peak system performance. The kit has 50M51-843 universal replacement control for two-stage automatic gas ignition that controls employing a microprocessor to continually monitor, analyse 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.

• Input voltage of 24VAC, 60Hz (class II transformer required)
• 120VAC ignitor, two-speed inducer, humidifier, electronic air cleaner, 3-speed PSC circulator o/p
• Nominal input current at 24VAC at 530mA + MV, fuse protection is 3A, furnace status LED
• Gas valve relays of 1.5A at 24VAC, 60Hz, inducer relays of 2.2 FLA to 3.5 LRA at 120VAC
• Circulator relays of 14.5 FLA to 25 LRA at 120VAC, humidifier load of 1A max at 120VAC
• Electronic air cleaner load of 1A max at 120VAC, ignitor relay of 4A max at 132VAC, 60Hz
• Operating temperature range from -40° to 175°F (-40° to 80°C)
• Timing specifications (at 60Hz) flame failure response time sec max
• Dimension is 5.25" W x 8" H x 1.25" D
• Natural, manufactured, mixed, liquefied petroleum and LP gas air mixtures are approved gases for use

Applications

Automation & Process Control

Contents

50M51-843 ignition control module, 21D64-2 HotRod™ universal ignitor kit, Installation instructions, OEM cross-reference.