The Hurst 500 Series four-pass wetback scotch marine boiler is an ideal choice for all commercial and industrial applications when engineering mechanical systems using the latest HVACR technologies. The Hurst 500 Series boiler provides fuel efficiencies that exceed most four-pass designs. Having no large refractory rear door, these boilers allow one technician easy access to all tubes. The boiler front doors can be opened without removing any burner components or controls.