(a) Electric motors larger than ten (10) horsepower shall be three-phase, except by special approval of the director.

    (b) The starting current for any three-phase motor shall not exceed eight (8) per cent of the full load capacity for the department's distribution feeder which serves the motor. The maximum size motor which will be permitted to start across the line without current limiting starters for various feeder voltages, is as follows:

(Code 1964, § 15.520)