The NuTone FG7SD/M residential gas furnace is a single-stage, fixed-speed model. The 95 percent AFUE furnace is available in upflow/horizontal and downflow configurations. Units range in capacity from 38,000-120,000 Btuh. Features include an insulated blower compartment for quiet operation, SmartLite® technology for longer igniter life, diagnostic troubleshooting lights for ease of servicing, and a low-boy height to accommodate tight spaces and higher-SEER coils. The 30-second delay ensures a warm duct temperature at furnace start-up. The 30-second post-purge increases the life of the heat exchanger. The color-coded wire harness is designed to fit the components, all with quick-connect fittings for ease of service and replacement. The flexible category IV venting system may be vertically or horizontally vented using either a one- or two-pipe system. The furnace is LP (propane) convertible. Diagnostic troubleshooting lights feature a dedicated light for flame signal strength and two lights in combination to indicate all other fault codes.