Goodman GMH81005CX Gas Furnace, Two-Stage Burner/Multi-Speed Blower, Upflow/Horizontal Low NOx 80% AFUE, 3-5 Ton 1/2 HP - 100,000 BTU Patented TuffTube&trade; dual-diameter tubular heat exchanger Two-stage gas valve with revolutionary new Dual$aver control technology that allows installer to turn on two-stage operation with the flip of a dipswitch Silicon Nitride igniter with patented adaptive learning routine for maximum igniter life Energy-saving, quiet four-speed direct-drive circulator blower motor Integrated electronic furnace control board with self-diagnostics, low-voltage terminal block, and separate terminals for elec