Copyright (c) Marc Dacey/Dark Star Media unless otherwise indicated. Above photo (c) Marc Dacey. Powered by Blogger.


Splendid isolation

Behold the Yandina Galvanic Isolator: It's like a check valve for stray currents.
Take a deep breath, sailors: This may get technical.

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.

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.
Acting with the guidance of a trusted source, I determined the galvanic isolator was functioning and then found a logical, shady place to mount it (it's not a large thing).  Then out came the shore power plug and I broke out the Holy Trinity of electrical hand tools: my Klein cable cutters (obtained in a junk store for five bucks), my Ideal Stripmaster and my Ancor double crimper.
Of course, even though I replace this typical cord when it shows signs of wear, there are better options these days.
Firstly, I had to cut into the 30 amp line. Keen eyes will spot a second 30 amp line and yes, we can run them combined for 60 amps, but I've never bothered. The throw switch seen to the left of the shot here is the "30A/off/60A" option, but it's never been an issue. If it becomes one, I can alter this installation.

The scribble refers to which outlet on the pilothouse exterior this cable is attached.
Carefully scoring the outside cover to reveal the green ground wire, I opened up about 15 cm. There was no need for any more to be exposed.
Stripping. I live for it.

My old friends, the heat-shrinkable butt crimp connector. That doesn't even sound rude anymore.
Crimping the isolator into the ground circuit was straightforward. Still haven't quite figured out the +/- adjustment on the crimper, however.
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.
Now, while the rationale for this installation is clear to me,  the world is full of crappy shore power circuit connections and dodgy boats. I may not be entirely done. There's an argument (particularly on metal vessels) for installing a larger, bulkier and more expensive item known as an isolation transformer. It's the electrical equivalent of wearing a wellie in a whorehouse should one wish to avoid the clap of galloping corrosion. The arguments in favour of it are strong, but I would need to see more benefits in the form of a longer record of anode wastage on Alchemy. Certain factors are currently (no pun intended) influencing the lack of enthusiasm for installation of an isolation transformer. Firstly, we will be on the hook (and therefore not on the shore power) in most places we visit. Not being on shore power, and not being near other boats on shore power is more than half the battle in reducing galvanic corrosion issues. Secondly, we don't have a generator built into the boat...and tied into its AC circuitry. It's all DC, from panels to wind genny to battery bank. Unless we are inverting DC to AC, there's no AC. We will have AC also in the form of Honda 2000 portable generators, definitely one and possibly two, but they aren't attached to the boat directly.
Not to code, hell, no
That judgment rendered, there's some squirrelly stuff on the docks at my club. Spend a few weeks in blistering heat wiring out things and one starts to dwell on it. A guy three slips down has been running two domestic-grade (think 16 gauge garden variety you'd use to power a weed whacker) from his wee charger on his '70s-era boat (wired probably identically to Valiente) across his decks, off his bow, over the water and down a bow dock line. From there it goes to the power post I share with a cabin cruiser that is constantly drawing 60 amps to keep the beer cold. When I asked why, the owner said the "power post closest to him doesn't have a working 15 amp plug". Well, that's really a club issue the boat owner has. Letting a live extension cord dip into the water next to my steel boat is my problem. He's since pledged to get a 30 amp cord. Hell, he's paying for the dock.
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.
Yet this stuff is distressingly common on the docks. Either through a perception that "well, I only need enough power for the clock radio/Koolatron/little 10 amp battery charger" means only an extension cord is necessary, or because the club is negligent or ignorant on how poorly crappy cords and water mix one sees this far too often.
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.

No comments: