Steel Hull 110vac

[brutb]

What is the best way to install a 110vac system on a steel hull and deck sailboat? Will this help minimize electrolsis?

[S/V Alchemy]

No, but it has the potential to make it a lot worse.

Installing both AC and DC on a steel boat is tricky, somewhat learned business. I recommend both books and course...and then I recommend an electrician familiar with "floating grounds", "galvanic isolators" and "drive savers"...because after the books and courses you will understand what the hell he's talking about.

A good place to start is this book: Amazon.com: Metal Corrosion in Boats (9781574090543): Nigel Warren: Books

Anyone owning a steel boat who wants to make the experience permanent should own it.

[Ike]

Very good advice from Alchemy. I don't normally suggest going to another forum but in this case the forum on the Metal Boat Society website has had many discussions on electrical installations. Welcome to the Metal Boat Society

[goboatingnow]

It's not complicated just follow some rules
Use an isolating transformer
If possible isolate the hull from dc. Use isolated starters and alternators. I would not bond underwater objects together. No connection between onboard DC negative and earth.

The traffo solves most of the problems
Dave

[brutb]

Thanks,guys I knew that someone on this forum would have sensible answers. I will look at the Metal Boat Society and start reading.

[S/V Alchemy]

Originally Posted by goboatingnow

It's not complicated just follow some rules

So you'd think. But since I bought a steel boat, I've seen some horror stories on other steel boats. As far as I can tell, it's a fundamental shortfall in understanding how electricity works in creating galvanic corrosion.

Marinas frequently don't get it right, either, and they have incentives not to electrify their basins.

[Southern Star]

As a previous owner of a steel boat I would concur with the answer already given: install an isolation transformer - you are then effectively isolated from the shower power supply and its failings. Yes, they are heavy (but so is a steel boat) and generate significant heat, but they work so long as everything is grounded back to them. One additional advantage is that many can also be used as a step-down transformer - ie, reducing 240 V to 120V if you travel to Europe or various places in the Caribbean.

Brad

[S/V Alchemy]

Not to divert the thread, but while I know I need an isolator, I have to acquire one, and therefore am seeking opinions and anecdotes. I have two chargers, a ferro resonant West Marine 40 amp "dumb" charger I will likely keep as a backup, and a 100 amp Xantrex charger/inverter (RS 2000 sine wave), for what it's worth.

[CharlieJ]

Not to divert the thread, but while I know I need an isolator

Isolators made by Dairyland Electrical Industries, Inc. Fail-Safe Galvanic Isolators | DEI Marine are robust and best in class, IMHO.

They are not cheap. They are the best.

Charlie

[S/V Alchemy]

Funny name for an electrical company. I'll check it out, though. Thanks!

[goboatingnow]

So you'd think. But since I bought a steel boat, I've seen some horror stories on other steel boats. As far as I can tell, it's a fundamental shortfall in understanding how electricity works in creating galvanic corrosion.

Marinas frequently don't get it right, either, and they have incentives not to electrify their basins.

Theres isnt a lack of understanding. On a steel boat in particular, there is a compromise between ultimate electrical safety and induced corrosion. Then add cost on top of that and you get all these conflicting rules and regulations and suggestions and codes of practice.

Just to summarise,

(a) In my opinion steel boats need an isolating transformer, if you intend to bring AC onboard. Stray current corrosion is real big issue in steel. Isolating traffos, effectively remove this issue. Galvanic isolators are not good enough


(b) The DC neagative and AC protective earth in such a case as above, should not be connected. Use RCD's on the shore power input and on the output of the traffo. These are your main protective devices. Traffos remove the most common problem of AC shorts to ground.

(c) Not connecting the DC and AC ( I completely disagree with ABYC on this point) does not significantly compromise safety ( with RCDs) and isolates each section from stray current and load dumping into each others circuit.

(d) If you can isolate your engine block, isolated starter and alternator, not difficult.

(e) I am not convinced of the merits of whole boat bonding, ( Michael Kasten has a good run down on this). Whole boat bonding is an American thing. Its rarely if ever done in Europe. ( and we build a lot of steel boats)

Note that Galvanic corrosion, will always occur, where disimilar metals are connected via a dielectric, induced or stray current corrosion is what we are trying to prevent here, while remaining within a overall safety paradigm.

Dave

[S/V Alchemy]

Thanks for this run-down.

To what would you bond the zincs, then? I know to zinc the shaft and the rudder, but I have yet to install hull zincs of the "flat lonzenges thru-bolted" type.

I agree that it's easier to bond a GRP boat, and I got rid of the green wire connecting all my thru-hulls there without harm, but I'm in fresh water and can't easily experiment. I have to fully grasp the niceties of this before I relaunch the steel boat next spring, after putting in a new engine.

[goboatingnow]

I would not have bonding on steel vessels. See http://www.kastenmarine.com/corrosion.htm for a good view point

Dave