Originally Posted by CharlieJ
The fail safe GIs utilize extremely rugged components and the unit is tested and certified by a third party. The testing protocol sorts out the contenders from the pretenders.
A “Fail-Safe” galvanic isolator will “fail closed-circuit”; insuring that the shore power safety
ground wire is maintained through the isolator, even in the event of isolation failure.
The criteria for galvanic isolators is defined by the American Boat and Yacht Council (A
BYC) recommended standard A-28, which has recently been revised. This standard has a publication date of July 2008 and an effective date of July 2009.
Due to recommendations to the A-28 galvanic isolator standards committee concerning the need to retain safety
grounding under all conditions, as required by the U.S. National Electric
Code for all similar applications outside of A-28, this standard now makes provision for fail-safe galvanic isolators.
To be considered "fail-safe," an independent laboratory must confirm that the isolator will either remain fully functional or remain a permanent, effective grounding path if it fails when subject to the maximum current rating.
Per the new A-28 standard, galvanic isolators meeting the fail-safe requirement will not require a monitoring system since the integrity of the grounding wire will not be compromised should the isolator fail.
All galvanic isolators not meeting the fail-safe criteria will still require a monitoring system to alert the boat owner that their grounding system may be compromised.