The Goodman GMH95 is a multi-speed gas furnace with an AFUE rating of up to 96 percent. The unit has a convertible two-stage gas valve, an aluminized-steel tubular heat exchanger and a 110-volt silicon nitride igniter.
"Multi-speed" refers to the number of speeds, generally three, on a furnace's blower fan. The first speed is used for heating, and medium and high speeds are used for home cooling. AFUE, or annualized fuel utilization efficiency, is a standardized measurement of a gas furnace's efficiency. The percentage represents the amount of energy expended by a furnace that actually heats the residence. When subtracted from 100, the remaining number represents heat vented by the chimney.
A two-speed gas valve allows a gas furnace to work either at full capacity or 60 percent capacity. The furnace begins to heat at the lower capacity, switching to full capacity if heating demands cannot be met. This causes longer heating cycles, spreads heat more evenly and is more energy efficient. A heat exchanger is the compartment in a gas furnace where the gas is burned and the heat is transferred to the air. Carbon monoxide leaks occur when the structure of a heat exchanger is compromised. Silicon nitride igniters fail less frequently than traditional gas furnace igniters.