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Friday, 18 March 2016

Electric - Part 2... Galvanic Isolation

Sorry about yesterday... it had been a long, tiring and stressful driving day - dumped on me at short notice.  It did nothing to ease my back which is really bad at the moment but such is life.


Lots of people pretend there is no need for a galvanic isolator on their boat - citing they will never use shore power.

We may well be the same but future proofing is something we're keen to do.  After our first winter on the cut, we may well decide to take a winter mooring in a marina and hunker down during the worst of it... taking advantage of shore power to make life that bit easier.

With that in mind, we're going to fit a galvanic isolator to the boat.    They come in various shapes and forms:

WHAT DOES IT DO? (I hear you ask)...

The short answer is that it protects your sacrificial anodes and hull from corrosion caused by stray electric currents.

The longer answer however is that when you plug into mains shore power, the cable you use has 3 internal cables: A live, a neutral & an earth wire. Thearth wire goes to the shore power bollard where it is physically connected to the ground.   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 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 need to install a galvanic isolator in the earth wire as it comes to our boat. The isolator is an electronic switch which is "Turned off "... This stops any low level damaging voltages from entering our vessel & protects our anodes, underwater metals AND  in the case of an electrical short circuit on board, the isolator immediately "turns on" connecting us to earth for safety.

IT's another expense that we could avoid or delay, but I'm happier getting things "right" from the start.

I've run out of time again  - part 3 to follow.

Until next time...

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