GMH81405DN

Dual-diameter tubular heat exchanger • Two-stage gas valve control technology allows installer to activate the two-stage valve with the flip of a dipswitch • 110V Silicon Nitride igniter • Quiet four-speed direct-drive circulating blower motor • Furnace control board with self-diagnostics, colorcoded low-voltage terminals and provisions for electronic air cleaner and 24-volt humidifiers • Control board stores the last five diagnostic codes in memory; simple push-button activation outputs the fault history to a flashing red LED • Low constant fan allows homeowner to activate the low heat speed to efficiently circulate air throughout the home • Self-adjusting feature automatically adjusts furnace to high- or low-stage operation based on outside temperature without an outdoor temperature sensor • Certain models available with low NOx emissions