MSHA - Code of Federal Regulations - 30 CFR 75.803
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MSHA - Title 30 CFR
30 CFR § 75.803
Fail safe ground check circuits on high-voltage resistance grounded systems.


On and after September 30, 1970, high-voltage, resistance grounded systems shall include a fail safe ground check circuit to monitor continuously the grounding circuit to assure continuity and the fail safe ground check circuit shall cause the circuit breaker to open when either the ground or pilot check wire is broken, or other no less effective device approved by the Secretary or his authorized representative to assure such continuity, except that an extension of time, not in excess of 12 months, may be permitted by the Secretary on a mine-by-mine basis if he determines that such equipment is not available.