---
kind: "section"
citation: "46 C.F.R. § 111.30-17"
title: "46"
number: "111.30-17"
heading: "Protection of instrument circuits."
url: "https://uscodex.org/cfr/46/111.30-17"
---

# §111.30-17. Protection of instrument circuits.

- (a) Each circuit that supplies a device on a switchboard, except a circuit under [paragraph (b)](#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)](#b) of this section, it must be set at not less than 500% of the expected current.
- (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.

## Notes

### Authority

Authority: 46 U.S.C. 3306, 3703; DHS Delegation No. 00170.1, Revision No. 01.2. Section 111.05-20 and Subpart 111.106 also issued under sec. 617, Pub. L. 111-281, 124 Stat. 2905.

### Source

Source: CGD 74-125A, 47 FR 15236, Apr. 8, 1982, unless otherwise noted.