[Code of Federal Regulations] [Title 46, Volume 4] [Revised as of October 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 46CFR111.30-17] [Page 223-224] TITLE 46_SHIPPING (This book contains parts 90 to 139) CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PART 111_ELECTRIC SYSTEMS_GENERAL REQUIREMENTS--Table of Contents Subpart 111.30_Switchboards Sec. 111.30-17 Protection of instrument circuits. (a) Each circuit that supplies a device on a switchboard, except a circuit under paragraph (b) of this section, must have overcurrent protection. (b) A circuit that supplies a device on a switchboard must not have overload protection if it supplies: (1) An electric propulsion control; (2) A voltage regulator; (3) A ship's service generator circuit breaker tripping control; or (4) A device that creates a hazard to the vessel if deenergized. (c) If short circuit protection is used in any of the circuits listed in paragraph (b) of this section, it must be set at not less than 500% of the expected current. [[Page 224]] (d) A secondary circuit of a current transformer must not be fused, and the circuit from a current transformer to a device that is not in the switchboard must have a high voltage protector to short the transformer during an open circuit.