Electrical Safety FAQ:
Multiple Power Source Warning Requirements
What does 46 CFR 143.250(b) require?
Federal regulations require that any electrical panel or enclosure containing more than one power source be clearly labeled with a warning sign. This sign must:
- Alert personnel that multiple power sources exist, and
- Identify where each power source can be secured or disconnected.
Why is this requirement important?
Electrical panels with multiple power feeds—such as shore power, generators, or battery systems—can remain energized even when one source is shut off. Proper signage prevents electrical shock, arc flash, and equipment damage by ensuring workers know all potential sources of energy before performing maintenance or service.
What should the warning label say?
While the regulation allows flexibility, the wording must be clear, visible, and specific.
Example label:
Warning: More than one power source. Disconnect shore power and generator supply before servicing.
Labels should be made of durable material, resistant to heat, moisture, and corrosion.
Where should the warning be placed?
Place the warning directly on or adjacent to the panel or enclosure in a conspicuous location, easily seen by anyone accessing the equipment.
Who is responsible for compliance?
Vessel owners, managing operators, and masters are responsible for ensuring all applicable panels and enclosures meet this labeling requirement.
How is compliance verified?
Compliance with 46 CFR 143.250(b) is verified during:
- U.S. Coast Guard inspections
- Authorized Class Society (ACS) surveys
- Annual Surveys (for Subchapter M vessels)
Best practices for maintaining compliance
- Inspect labels regularly and replace if damaged or faded.
- Update signage whenever power configurations change.
- Use engraved placards or marine-grade adhesive labels.
- Train all crew and maintenance personnel on the meaning of the signs.
