Galvanic Isolators

[Ken Juul]

When I recently installed my new water heater, I got a nice warning in the box about using a Galvanic Isolator to prevent the small DC current from running between the boat and the dock through the ground wire in the power cord.  I have a Guest Model 2520 battery charger.  Not much paper about it.  Not sure if it is original equipment or an add on.  If it came with the boat it would make it a 1989/90 model, an add on could be newer or older. Looking at the Guest web page, they say the chargers have a built in isolator.  Anybody know if all model years of the 2520 have this feature?  Will this stop the current the warning mentioned?  Have emailed Guest, but have not yet recieved a reply.  Happy Sailing

[jmnpe]

Your battery charger might have an isolation transformer, but not a true galvanic isolator. The isolation transformer will only break any conductive paths between the Line and Neutral legs of the AC input lines. The galvanic isolator breaks the low level conductive path through the ground, or green, wire of the AC shore power circuit to the boat.

Guest make a couple of galvanic isolators, as does Newmar and Professional Mariner. You would want a 30 amp model. All of them come with simple installation information, I believe. They install very easily in the green wire circuit between the shore power feed and the rest of the "green" circuits on the boat. The isolator will prevent low level DC or AC currents from flowing from the shore ground to the water through any grounded metallic objects on your boat that are in contact with the water either directly or indirectly. If you have a major AC fault in the boat, then the isolator will still allow conduction back to the shore power ground.

Joh