Do I need a galvanic isolator?
1. Whenever you connect to shore power mains supplies. An isolator offers reduced corrosion & extended life of anodes.
2. Leave your shore power connected enabling use of frost heaters & battery charging without the risk of added corrosion associated with shore power connections.
3. Essential in the marina environment to control both stray & galvanic currents.
4. * When you need to stop other vessels using your anodes!
When you plug into mains shore power the cable you use 3 internal cables: A live, a neutral & an earth wire. The earth wire goes to the shore power pedestal where it is physically connected to the ground. This is a safety wire and protects you in the case of an electrical problem.
Your neighbouring boats also use the same earth connection. This effectively connects all the boats together via the earth cables in the shore power leads. In your boat the shore power earth lead goes to your electrical consumer unit & then to all metal components such as the engine block, fuel tanks, shafts/ propellers etc & then finally connects to your anodes. Unfortunately as all the boats (and metal pontoons) are now interconnected via the earth cables any voltage leaks or "galvanically" generated voltages have an easy path between the boats. This often results in rapid loss of sacrificial anodes & increased corrosion of all underwater metals. If the boat next to you does not have anodes he won't worry: He is using yours!
To control this problem we install a galvanic isolator in the earth wire as it comes to your boat. The isolator is an electronic switch which is "Turned off " (open circuit). This stops any low level damaging voltages from entering your vessel & protects your anodes and underwater metals. In the rare case of an electrical short circuit on board your vessel the isolator immediately "turns on" (short circuits) connecting you to earth for safety. The isolator works in perfect conjunction with fuses, circuit breakers and RCD safety devices. It is a solid state device & resets itself once the electrical fault has been rectified.
A galvanic isolator does not replace your sacrificial anodes which are essential to protect your underwater metals from interaction of metals.
A galvanic isolator does offer protection from stray currents & galvanic currents which attack your boat via the shore power earth cable. These currents can transmit from other boats, metal pontoons & leaks on the 240 volt systems in the marina. Serious leaks can devastate your props / shafts/ anodes etc in a matter of weeks. Surveyors & boat inspectors will usually recommend fitting a galvanic isolator in the marina environment (They see the effects of unprotected boats all too often).
Happy Cruising from all at Venetian Marina.