Programmable Thermostat

The Lennox 100870-01 is a two-stage variable speed furnace ignition control board engineered to serve as the central command system for compatible Lennox HVAC units. This integrated control board, also known as a SureLight board, coordinates all furnace components, monitors critical sensors and safety switches, and distributes voltage throughout the system to ensure reliable heating and cooling operation. This replacement control board supports both single-stage and two-stage thermostat configurations, with selectable operation via DIP switch settings. When paired with a single-stage thermostat, the board intelligently switches to second-stage heating after 30 seconds to maintain optimal comfort levels. The variable speed blower control feature provides customizable blower off delays for both heating and cooling cycles, with heating delays adjustable via DIP switches 1-2 (factory setting 90 seconds) and cooling ramping adjustable through switches 9-10 to support enhanced dehumidification while maintaining target supply air temperatures of 90-110 degrees Fahrenheit. Designed for straightforward installation and maintenance, this control board is a direct replacement for original equipment on compatible Lennox furnace models. It is constructed to deliver reliable performance in demanding HVAC applications across residential and light commercial installations. The board's robust engineering and flexible configuration options make it an ideal choice for technicians and facility managers seeking dependable, cost-effective control solutions for Lennox heating systems.