|Behold the Yandina Galvanic Isolator: It's like a check valve for stray currents.|
Boat electrics are a complex and an even nuanced subject. Not only are knowing the basics of wiring out AC and DC circuits necessary if you want to run your own liveaboard show, but the special situations of a) boats sitting in weak electrolyte and b) metal boats sitting in weak electrolyte must be appreciated. Some terms are inexact or differ among the English-speaking peoples, such as "line or hot, neutral, ground or earth", while others, such as "floating ground", give rise to unintended images of hovering turf.
Part of the battery rehab has been, of course, the installation of the inverter, the device that creates AC power from DC power stored in the house battery bank. Learning about how that circuit is tied into the existing AC ground (see "floating") suggested that I should improve the shore power situation with galvanic isolation, which, in basic terms, stops stray currents in the water, a fluid highly conductive of voltage, from dodgy dock electrical supply, people dropping live extension cords in the water, or people whose boat wiring is not up to spec and who may consequently be leaking volts into nearby water.
|Diagram (c) Boat U.S. http://www.boatus.com/|
This is a problem with many solutions, all of which make great bedtime reading for people like me, and which can be exacerbated on metal boats. Not to mention that in severe cases, which may nonetheless be insufficient to trip the breakers designed to protect the circuit, the waters can become sufficiently electrified to injure or kill swimmers, the gravity-prone or kids messing about in nearby boats, who fall in all the time. It's not just the zinc anodes that suffer.
I can note and complain about flaws in my own club's wiring, and, as you'll read below, there are problems. But I can't actually fix them myself. I can, however, protect my boat. The Yandina gadget is one step in that direction.
|Measuring the diodes in one direction...|
|...and then the other. Both were within spec, according to the manufacturer's instructions.|
|Of course, even though I replace this typical cord when it shows signs of wear, there are better options these days.|
|The scribble refers to which outlet on the pilothouse exterior this cable is attached.|
|Stripping. I live for it.|
|My old friends, the heat-shrinkable butt crimp connector. That doesn't even sound rude anymore.|
|After applying the heat gun, it looks reasonably weatherproof. Given that it's in the companionway to the aft cabin, opportunities to experience weather should be quite limited.|
A few cable ties to neaten up my work and I was done. Plugged back in, there was no evidence I had done a thing, and yet I had protected my boat from current events.
|Squared away, yet still accessible should that be necessary.|
|Not to code, hell, no|
|See that white fuzzy thing in the middle of the shot? That's the outer cover and inner fuzz exposed because the cord's nearly cut through.|
|Black electrical tape does not, in fact, keep the electricity in.|
I use "pro-grade" 12 ga. extension cords on occasion to run tools while I've got the AC circuitry in pieces on the deck. I secure it to the dock and wrap it up when I'm done. I don't leave the boat plugged in generally, because of what I've learned. The battery bank will shortly be on solar and wind...I won't have to plug it at all if I'm not running power tools. These concepts aren't hard, but remain, in my view, poorly understood. Since I started sailing in 1999, there have been three serious firest at nearby facilities: a fire at RCYC caused by a battery charger left plugged it via an extension cord that burned several boats; a fire at QCYC caused by leaving a fridge plugged into an extension cord (that one nearly burned the club down, if I recall correctly); and a fire at Outer Harbour Marina from an extension cord plugged into a heater in the on-site toilets. I saw the results of that one personally:
|It did not buff out.|
The commonality, of course, is the lowly, unattended, probably hot and overamped extension cord. They are, unless really expensive and made for mud-caked construction sites (I have 150 feet of those and use them as needed over the winter) made for temporary, light duty. They aren't waterproof and the longer they are, the more likely they are to melt. The 30 amp shore power cord, with the right adapter, is the only acceptable power cord that should be seen at a marina or yacht club unless it's in active, supervised use.
|Yikes. An argument for hauling out if I've ever seen one. Photo (c)|
I realize that extension cords are easy and that shore power cords are unwieldly, heavy and expensive. I don't care. Your negligence doesn't get to burn (or corrode) our boat. Send your hate mail care of this blog.