Ships have electrical power systems that are (supposed to be) wired differently than shore side power systems.

In a shore-side power system, a standard three prong AC power outlet is wired so that one of the two "power" slots (commonly referred to as "neutral") and the ground are at the same electrical potential. The third slot is "hot". The electrical potential between the hot and either the neutral or the ground is 115 volts of alternating current (VAC.)

On a ship, the AC wiring is different, there is equal electrical potential between the ground and both the neutral and the hot legs. This is done to prevent a "grounded" wiring system from electrically corroding the hull away.

This difference in wiring means that:

• Power switches on ships need to turn off both legs of a typical 115 VAC circuit, not just the "hot" one as in a shore side system
• a failure (short to ground) of one hot lead will continue to provide power to the load when such a failure in a shore side system would blow a fuse or breaker, and
• can result in high current under some failure modes that can exceed the rating of transient suppression components (Transorbs etc.) in power conditioning equipment.

Provisions for these differences are typically not incorporated in common off the shelf (COTS) equipment designed for use ashore.

UPSs:

Outlet Strips etc.:

References:

• [FTP link] MIL-STD-1310G STANDARD PRACTICE FOR SHIPBOARD BONDING, GROUNDING, AND OTHER TECHNIQUES FOR ELECTROMAGNETIC COMPATIBILITY AND SAFETY
• USCG boating safety, electrial systems note
• UC Berkley Power Point about Submarine Power Systems
• NAVSEA Shipboard Power Safety PDF file.

Listing here does not imply endorsement of any particular vendor or product.

Comments, additions, corrections, suggestions to Dale Chayes