You have entered a value in the highlighted fields below that contain invalid characters. Please revise your selection using valid characters only.

Product may not be an exact match for your search

You previously purchased this product. View in Order History



Furnace Control Kit, HSI Integrated, Universal, Two Stage, 3 Speed PSC Circulator, 120 Vac


Image is for illustrative purposes only. Please refer to product description.

Manufacturer Part No:
Newark Part No.:
Technical Datasheet:
21M51U-843   Datasheet
See all Technical Docs

Product Information

Want to see similar products? Simply select your required attributes below and hit the button ×

Ignition Ctrl Mod, Universal Ignitor Kit, Installation Instructions & OEM Cross-Ref


Find similar products Choose and modify the attributes above to find similar products.

Technical Docs (2)

Product Overview

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


Automation & Process Control


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

Best Seller

3 In stock

Order before 5.45pm EST standard shipping

Same day shipping

To order more than shown inventory, contact sales

Available in quantity shown


Pricing is unavailable. Please contact customer services.

Price for:
Multiple: 1 Minimum: 1
Quantity Price Your Price
1+ $315.90
Promotional price
Contract Price
Web only price
Web only contract price
5+ $306.86
Promotional price
Contract Price
Web only price
Web only contract price

Pricing is unavailable. Please contact customer services.

No longer stocked:: No Longer Manufactured::
Add to Cart Back Order Pre-Order
Restricted Item
Enter Your Part No/Line Note
Total Price:
Total Price: ( )
Total Price: --