The White-Rodgers two-stage HSI integrated circulator furnace control kits are available in both three speed and variable speed. The variable-speed Model 21V51U-843 replaces all White-Rodgers 50V51-XXX and 50V61-XXX two-stage HSI systems with 80- or 120-V igniter. The three-speed version Model 21M51U-843 replaces all White-Rodgers 50M51-242 and all 50M61-XXX two-stage HSI systems with 80- or 120-V igniter. Designed to help contractors reduce their inventory and simplify installation, the kits include ignition control module, universal 120-V nitride igniter kit - 21D64-2, installation instructions and OEM cross-reference, and quick-select/quick-connect wire harnesses (for only the 21V51U-843). The kit also offers improved system diagnostics and protection with features such as stored fault recall, a red LED light used for diagnostic flash codes, and a cover label that contains diagnostic fault codes for convenient reference.
Emerson Climate Technologies, St. Louis, MO; www.white-rodgers.com