---
kind: "section"
citation: "46 C.F.R. § 143.555"
title: "46"
number: "143.555"
heading: "Electrical power sources, generators, and motors."
url: "https://uscodex.org/cfr/46/143.555"
---

# §143.555. Electrical power sources, generators, and motors.

- (a) **General requirements.**
  - (1) There must be a source of electrical power sufficient for:
    - (i) All essential systems as defined by [§ 136.110](/cfr/46/136.110.md) of this subchapter;
    - (ii) Minimum conditions of habitability; and
    - (iii) **Other installed or portable systems and equipment.**
  - (2) Generators and motors must be suitably rated for the environment where they operate, marked with their respective ratings, and suitably protected against overcurrent.
  - (3) A towing vessel, other than an excepted vessel, must have a backup or a second power source that has adequate capacity to supply power to essential alarms, lighting, radios, navigation equipment, and any other essential system identified by the cognizant OCMI or a TPO.
- (b) **Specific requirements.**
  - (1) The owner or managing operator must complete a load analysis that shows that the electrical power source is sufficient to power the sum of connected loads described in [paragraph (a)(1)](#a-1) of this section utilizing an appropriate load factor for each load. A record of the analysis must be retained by the owner or managing operator.
  - (2) Installed generators and motors must have a data plate listing rated kilowatts and power factor (or current), voltage, and rated ambient temperature.
  - (3) Generators must be provided with overcurrent protection no greater than 115 percent of their rated current and utilize a switchboard or distribution panel.
  - (4) Motors must be provided with overcurrent protection that meets Parts I through VII, Article 430 of NFPA's National Electrical Code (NEC) (incorporated by reference, see [§ 136.112](/cfr/46/136.112.md) of this subchapter). Steering motor circuits must be protected as per [Part 4](/cfr/46/part4.md) Chapter 6 [Section 2](/cfr/46/2.md), Regulation 11 (except 11.7) ofABS Rules for Building and Classing Steel Vessels Under 90 Meters (295 feet) in Length (incorporated by reference, see [§ 136.112](/cfr/46/136.112.md) of this subchapter).
  - (5) Generators and motors installed in machinery spaces must be certified to operate in an ambient temperature of 50 °C or be derated, or it can be shown that 40 °C ambient temperature will not be exceeded in these spaces.
  - (6) Each generator and motor, except a submersible-pump motor, must be in an accessible space which is adequately ventilated and as dry as practicable, and must be mounted above the bilges.
  - (7) A generator driven by a main propulsion unit (such as a shaft generator) may be considered one of the power sources required by [paragraph (a)](#a) of this section.
  - (8) Other than excepted vessels, each towing vessel must be arranged so that the following essential loads can be energized from two independent sources of electricity:
    - (i) High bilge level alarm required by [§ 143.230](/cfr/46/143.230.md);
    - (ii) Emergency egress lighting, unless the requirements of § [143.410(b)(1)](/cfr/46/143.410.md?p=b-1) or [(2)](/cfr/46/143.410.md?p=b-2) are met;
    - (iii) Navigation lights;
    - (iv) Pilothouse lighting;
    - (v) Engine room lighting;
    - (vi) Any installed radios and navigation equipment as required by §§ [140.715](/cfr/46/140.715.md) and [140.725](/cfr/46/140.725.md);
    - (vii) All distress alerting communications equipment listed in §§ [140.715](/cfr/46/140.715.md) and [140.725](/cfr/46/140.725.md);
    - (viii) Any installed fire detection system; and
    - (ix) **Any essential system identified by the cognizant OCMI or TPO, if applicable.**
  - (9) If a battery is used as the second source of electricity required by [paragraph (b)(8)](#b-8) of this section, it must be capable of supplying the loads for at least three hours. There must be a means to monitor the condition of the battery backup power source.

## Notes

### Authority

Authority: 46 U.S.C. 3103, 3301, 3306, 3308, 3316, 8104, 8904; 33 CFR 1.05; DHS Delegation No. 0170.1.

### Source

Source: USCG-2006-24412, 81 FR 40101, June 20, 2016, unless otherwise noted.