The design feature for the standard model from FB-B-004 to FB-B -060 is vertical tubeless. Fulton boilers have no tubes or coils, eliminating the problem of tube failure and providing efficient, safe, and reliable service. As Fulton's power burner spins the flame down the length of the furnace, water is induced to spin upward in the water vessel, reducing the possibility of stratification.

The standard model from FB-A-080 to FB-A-130 is a vertical multi-port boiler. A series of heavy walled large diameter schedule 80 flue pipes are welded to the top and bottom heads in the pressure vessel. These pipes are surrounded by water. This wet back feature design speeds up boiler startup and creates overall even heating throughout. The other design feature for this type of design is the "ribboned" turbulators that extend the gas-travelling length inside each flue pipe. The top mounted down-fired burner is an air pre-heat design enhances the boiler efficiency.