These fans are suitable for operation against moderate resistances. They are reversible and most are suitable for speed regulation. The motors are totally enclosed, having ball bearings which are sealed during motor assembly. Single phase motors are capacitor start-and-run type; Three phase motors are standard squirrel-cage design. Insulation is Class E (Class F available on request) and the motors comply with BS 5000, Part 11. The fans are fitted with square mounting plates.