Goodman GMH80805CN Gas Furnace, Two-Stage Burner/Multi-Speed Blower, Upflow/Horizontal - 80,000 BTU Patented TuffTube dual-diameter tubular heat exchanger Two-stage gas valve with revolutionary new convertible technology that allows installer to activate two stage operation with the flip of a dipswitchSilicon Nitride igniter with patented adaptive learning control for maximum igniter lifeFurnace control board with self-diagnostics, color coded low-voltage terminals and provisions for electronic air cleaner and 24 volt humidifiersControl board stores the last five diagnostic codes in memory; si