Galvanic Isolator SPP-ZS16A

It's a Marine thing: only those with a metal hull are mindful of when connected to shore power.

Sterling Power - Pro Save A 16A

Features:

• LED indicator for 2 volt passing variant (the first sign of a problem)
• LED indicator for product failure

Without the notification, you will think all is fine and the first you'll know of an issue is the non-existent anodes on your boat, or a rounded prop or a leaking boat.

THE PROBLEM:
Recent interest in damage done to boats due to the 230V shore mains has highlighted the need to fit a galvanic isolator to your boat.
In order for modern boat builders to comply with modern CE standards such as EN ISO 13297 they must fit the shore earth wire to your boats bonding system which is also connected to the hull / anodes / fuel tanks / engine blocks / shafts / propellers / stern tubes / rudders / rudder glands / water intakes / etc. This ensures that any 230V mains faults will operate the R.C.D on the boat in order to save your life.
The downside of these standards is that electrically speaking your boat is now connected to the rest of the boats in the marina and any other metal structures in the area. Electrically speaking they become one and the same. If you follow the earth line you can see everything bonded to the earth, this includes your boat, the one next to you, metalwork etc.
This results in two main problems.
1) Any earth problem on any boat or shore earth will increase the voltage in the common earth cable and dissolve - adversely affecting your boat by dissolving your anodes at an alarming rate (this could result in the total loss of all the metal on the boat below the waterline).

2) Because all the boats are now one if you have a zinc anode on your boat, but the boat beside you does not or even worse, the marina has not put anodes on its structures (metal pontoons etc) then your boat's zinc, (or aluminum/magnesium) will protect all the structures and boats around you, resulting in dramatic zinc loss and expensive lift-outs to replace the zinc. For boats on inland waterways, if you have a magnesium anode and everyone else has zinc or no anodes at all, your magnesium anode will protect all.

THE SOLUTION:
The trick is to maintain the continuity with the earth to ensure the safety of your life but remove the continuity with the shore power for the safety of your boat. The solution is very simple. By installing a Galvanic Isolator / Zinc Saver we maintain a good earth link with the shore but prevent any stray currents coming up the earth line and damaging the boat. The isolator is in theory a simple device but it has to be built to a stringent specification and tested by an independent test house to ensure they comply with the relevant standards, be it the less stringent CE standard or the more stringent American Boating and Yachting Council standard. This means in a major fault condition it can carry its rated current for 24 hours without exceeding 90 deg C on the heat sink.
The Galvanic Isolator has the following extra features:

By far the most commonly used device in Europe complies with all the requirements and is also low cost and very effective.