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Isolation Transformer

Nov 13, 2013
640
Catalina 34 Tacoma
My boat came equiped with an isolation transformer. While I have a general idea of what this does, I am not sure it is effective as currently installed or is suited for use on a fiberglass hull boat. Does anyone have experience usining one of these? Should I keep it of free up some space and just hard wire into shore power?
 
Oct 3, 2008
312
Beneteau 393 Chesapeake Bay
It might be an isolation transformer, or it might more likely be a galvanic isolator. The former is large, heavy, and expensive while the latter is less so in these respects. Both are intended to help isolate the boat from low voltage DC, thus limiting your corrosion due to galvanic action. A transformer will isolate all 3 wires (and the boat from shore power), while the isolator is connected only to the green ground wire. Galvanic corrosion is very common in some marinas, depending upon the electrical condition of the shore power system and other boats. You should keep it whatever it is.
 
Apr 2, 2011
185
Catalina 27 Niceville, FL
It's like chicken soup. Nobody knows for sure if it helps, but it couldn't hurt. Leave it alone.
 
Feb 6, 1998
11,436
Canadian Sailcraft 36T Casco Bay, ME
My boat came equiped with an isolation transformer. While I have a general idea of what this does, I am not sure it is effective as currently installed or is suited for use on a fiberglass hull boat. Does anyone have experience usining one of these? Should I keep it of free up some space and just hard wire into shore power?
It is not clear whether or not you have a true isolation transformer or a simple galvanic isolator.

Isolation Transformer = 100% Isolation of Boats AC Power From Shore AC Power

A true isolation transformer is rather large, may hum a bit, and completely and totally isolates your vessel from the other boats in your marina. It can not however save your boat from itself or on-board DC voltage/current leaks. Contrary to popular misconception most boats cause their own issues but marinas are pretty notorious for galvanic current issues..

An IT is the only product that can truly isolate your vessel because you do not have any direct connection to shore. Your boat is on one side of the windings and the shore is on the other. No connection! This of course is only true if they are properly wired. I have seen them installed where AC ground was tied to the metallic case and boat and Earth/Marina were still one in the same thus a complete and utter waste of good money was spent to install the IT to begin with.. Properly installed it is the only device, other than simply disconnecting your vessel from the marina, that works.

Galvanic Isolator = No Electrical Isolation From Shore Power
These devices prevent dissimilar metals galvanic currents from flowing into your boat. This galvanic erosion of your zincs or metals is caused by connecting your boat to other boats in the marina via the green/ground wire. When you plug into a marina you are physically connected to every other boat in the marina via the grounding wire. If another boat has no zincs they will now simply use your zincs to protect their boat, via the green wire.. If your boat has a less noble metal than other boats around you, and your zinc is gone or eroded or poorly installed, those boats will start making your metals the anodic metal.

Galvanic isolators do not prevent stray DC voltage leakage above 1.5V or on-board DC leaks / issues. They only prevent against galvanic corrosion of the voltages created by dissimilar metals immersed in an electrolyte traveling onto your boat via the green / ground wire.

If my own boat was in a marina it would have an isolation transformer, hands down.. A GI is a good cheap way to eliminate galvanic corrosion, but that is all they do...


P.S. If you don't want your isolation transformer, send it to me....:D