Disconnecting switches shall be installed underground in all main direct-current power circuits within 500 feet of the bottom of shafts, boreholes or at other places where main power circuits enter a mine.
52 P.S. § 690-324
Disconnecting switches shall be installed underground in all main direct-current power circuits within 500 feet of the bottom of shafts, boreholes or at other places where main power circuits enter a mine.
52 P.S. § 690-324