Available in wall-mounted units with a new fire tube design, the Knight® heating boiler offers up to 99 percent thermal efficiency. Fire tube models are available in seven models with inputs from 55,000 to 399,000 Btuh. They can be used for residential or light-commercial applications such as small hotels, schools, and office buildings. For higher demand applications, the Smart System™ operating control features a built-in cascading sequencer that allows up to eight units to be installed, delivering up to 3.2 million Btuh heating capacity. Features include low-NOx emissions, a fully modulating burner, and fully modulating 5:1 turndown burner, which allows the boiler to keep fuel use to an absolute minimum by adjusting heat output according to demand. Models are equipped for direct-vent installation with air intake and exhaust runs up to 100 feet using PVC, CPVC, or AL29-4C vent materials. The wall-mount units offer seven venting options and tremendous flexibility for placement within any building.