201342 Some surge protection devices unfit for vessels

Official Safety Alert from United States Coast Guard: Alert 03-13b

Most commercially available surge protection devices (SPDs) are designed for use ashore and will interrupt only the hot conductor when a surge occurs. What does that mean for the ship owner/operator? It means that while these devices may provide protection in our homes and offices, these same devices may be a fire risk onboard vessels.

A marine casualty investigation of two separate stateroom fires revealed that the sources of the fires were attributed to the use of SPDs plugged into a lighting circuit. It was discovered that a ground had developed on another circuit that was connected to the same distribution panel providing power to the staterooms. This ground created an imbalance of voltage between the two power conductors supplying the SPDs which caused excessive currents, overheating, and subsequently, a fire. In this instance, even if the SPDs automatically tripped as designed, only one power conductor would have been secured while the other would continue to provide power, possibly shorting to the device’s ground wire and the structure of the vessel.

For shipboard applications, it is critical for a device to interrupt both power conductors.

Vessels should have defined procedures for checking the condition and grounding capabilities of personal/portable electrical equipment, and trained shipboard personnel should be assigned to check and approve all SPDs in use or brought on board for compatibility with the vessel’s electrical distribution system prior to use.

Additional technical information
* This safety alert only applies to vessels with alternating current power systems.
* There is no official Underwriters Laboratory standard for Marine Surge Protective Devices despite numerous retailers advertising ‘UL Marine 1449’.

An SPD should be
* only permitted for use onboard once approved by a trained crewmember;
* removed from service if it is hot to touch;
* unplugged when not in use;
* regularly inspected for damage or wear;
* limited to one SPD per single duplex receptacle outlet and never daisy chained;
* prevented from use in excessively humid or moist environments;
* provided air circulation and not covered with carpet or other items, and
* checked to ensure that all plugs are fully engaged.