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  #1  
Old 02-16-2009
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Rewiring a relic--power advice? Electrical gurus?

We've got a 1968 Soverel 33 with several generations of kludged-together antiquated wiring and it's a general confusing mess (Lucas electrics FTL); I'm planning to totally redesign and rewire the thing so that it's suitable for fulltime liveaboards (two of us) and eventual cruising.

I'm no expert electrician, but I've rewired cars and planes, and I was an ET in the service. I have the basic skillset but no specific knowledge that is unique to boats. I'm not afraid to get in there and try stuff to get the thing to work.

At the moment it has a 10A charger and no inverter at all; we only have 120VAC while hooked to shore power; it's hardwired to the two AC outlets. No shore power, no AC.

What I want to do is upgrade the charger and install two inverters and a third outlet. The AC power load will mostly be light--two laptops and a printer, a small space heater, and a small fridge; but with occasional large loads from a microwave. The boat has a small DC fridge which we're keeping--ain't broke, so not gonna mess with it--and the DC lighting system, which I'm going to rewire for neatness and switch over to LED light ASAP. We're going to add a second fridge that can store more than a sixpack.

My specific plan is to go with a 30-amp switchable 2-stage/3-stage charger; a single 750W MSW inverter (bought dirt cheap at a pawn shop, not my first choice, but too good a deal to pass up) to power the one V-berth outlet; and a 2.0kW PSW inverter to power the saloon and galley outlets which will carry more sensitive electronic loads.

The 750W MSW inverter will carry an occasional load of ~600W (small space heater, plus a digital clock, plus a small hair dryer (the heater will be turned off while the dryer is on)).

The 2.0kW PSW inverter will carry a steady load of ~250W (two laptops and a printer) and an additional ~350W (second fridge running on AC) plus an occasional load of ~1500W (microwave). We'll power down the printer while microwaving.

The DC system will remain, powering the antique-but-functional minifridge, the interior lighting and fans, depthfinders, radio, cockpit stereo, and all exterior lighting. Again, I'm just going to rewire the Edison wiring and upgrade to LEDs.

First question, and by far the most important: Does any of this sound at all stupid; i.e. am I missing anything obvious?

Second question: Is it preferable to mount the inverters in the cabin, or in the engine space? Are there any regs that specify placement?

Third question: I know this will also require breaker panels, and those I am not as familiar with (not common in cars or small aircraft) but it should not be a major technical challenge; will I need two separate ones for AC and DC systems? Can I go with a "universal" panel that does it all?

Fourth question: Down the road we're planning to add solar panels and a wind jenny; does anything I'm planning now preclude these, or are there things I can set in place now to prepare for these additions later on?

Last question: Anyone in Charleston want to get in on this? I'll buy beer and pizza.

Edit: At the moment we have three batteries and I intend to add more.

Cheers!
Mike

Last edited by Sinuous; 02-16-2009 at 02:06 PM.
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Old 02-16-2009
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Marine Grade Wiring

Use primary wire to connect your batteries to positive and negative terminal plates. This should be around 6awg.

Marine grade wire is made of many thin strands, and each strand is coated in tin. This makes it flexible and corrosion resistant. I am not sure this is necessary (Cu is relatively non-reactive).

Marine grade heat shrink tubing has adhesive on the inside, and seals all terminals. Non marine grade would probably work... I mean, it is heat shrink tubing, I don't see why you would need adhesive.

Marine grade crimp-terminals are also tinned. Not a good place to skimp.

Do not use solder, it corrodes more easily than crimped terminals.
Do not use acorn nuts, not flexible, and poor conductivity can lead to fires.
Do not try to splice the wire by twisting it together, bad idea.

Battery switches are good.

Necessarily, this is all expensive.

Or just stuff it all and don't use the electric.
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Old 02-16-2009
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This is a really great book to start with.

Amazon.com: Boatowner's Mechanical and Electrical Manual: Nigel Calder: Books
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Old 02-16-2009
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My general comment would be do everything you can DC TO DC the inverters really suck up battery life


For example i cant see running a small electric heater off and inverter as something that would work at all without enough batterys to sink the boat
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Old 02-16-2009
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I have to agree with Tommays. Running a heater ac fridge microwave etc is not possible unless you have the sort of battery bank that that is too big to fit on a small yacht. (OK maybe microwave just)
The inverter may be large enough, but the battery bank needs to be able to supply the amps and the amp hours to the devices.
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Old 02-16-2009
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You seem to be on the right track.

I do not think you want to use a heater off an inverter.

You might consider using the small inverter for computer stuff and the other 2kw for house electrics. The inverters should be below deck. Frankly, I think you would be better off with a single inverter but that's just a preference for simplicity.

You should have AC and DC breakers and voltmeters. Panels come in many configs and boy, are they expensive.

I looked at the interior plan on the class website and am curious where the new fridge would go.
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Old 02-16-2009
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There are “no free lunches’ in electricity. You need to re-think your plan and perhaps purchase some more efficient appliances. You got a lot of “house” loads. 250W equates to 21 amps @ 12v. Assume that the refrigerator cycles half time. 350W / 2 / 12v = 15A. Assuming 10% inverter efficiency factor, you burning through your batteries at a rate of 40 amps without turning on a single lamp. Assuming further that you are installing a pair of 4Ds as a house bank and you will discharge down to 50% before recharge and an 80% recharge efficiency factor, you will have something like 130 AH. Usable storage capacity. Your drain will only give you a little over three hours before a charge is needed. Running a high output alternator (assume 50 Amp continuous), it will take you 2 and half hours to recharge. Of course, everything would have to be turned off during the recharge. You will have to make sure you have proper cooling on the alternator (You may have to run the engine blower during the recharge.) The large alternator will also rob several horse power from your engine. In effect, you will wind up running your engine at more than a fast idle while you are using your appliances. Your little shore charger will have no ability to keep up with your loads. Better to wire a dedicated 120V circuit for these house loads.
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Old 02-16-2009
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Tager: Good to know about the soldering; I was planning to do a lot of that.

Ajari: I have Calder's book, second edition, not sure if that's the most recent. Sought it out at the local used bookstore and got lucky.

Tommays: Okay, we're reconsidering and looking into propane heat and cooking. Reduce the power load.

Noelex77: Clearly I need to know more about amp-hours available from different battery types. A weak point in my knowledge thus far.

39512: Well, I got one inverter for a steal, but it's not enough. And you found online plans for a '68 Soverel 33? I've had no luck whatsoever; all I found was the '77+ racing boats. But the new fridge will go where the ancient alcohol stove used to be.

GeorgeB: Like I said, I clearly don't know enough yet about "big battery" endurance. But already I can see I need to lose the luxuries--microwave, heater--and look at chemical alternatives like propane for cooking and "comfort heat."
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Old 02-16-2009
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I Also have to rewire my boat so I read with interest about your plans. Fortunately I just had my boat surveryed, it's a 1972 Hughes, 29 foot sailboat. The surveyor was really helpful. I have Calder's book referred to above, it's quite expensive (50 dollars). I find it good on the mechanical stuff but not so lucid on the electrical side. But if you have ET experience from the military it's probably ok for you. Check it out of the library though. Or find someone who will lend you a copy. The AC wiring in my boat, wired (I use the term loosely) consists of household extension cords wire nutted together (no kidding). So I have to rip out all the old stuff. Regs now require the AC current to have a shut off switch (ie. it needs a box). My boat is currently on land in Maryland and I'd like to find someone with experience that could walk me through the wiring so I can learn the nuts and bolts of it. In the meantime I'm rereading Calder's book. I grew up on a farm so I have basic mechanical skills but marine electrics is really different, particularly the grounding arrangements. But I'm still optimistic I'll sort it out. I'm going to try not to use the rule that my old physics teacher told us during the unit on electricity: "Wire for the least amount of smoke!" Smoke is definitely not what I want to see when I'm off shore. Best of luck.
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Old 02-16-2009
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Roy1948: Well, I got twofold lucky on the book; found it for $20 at McKay's Used Books, where I also had hundreds of dollars in credit from recently trading in the brazillions of books, movies, and CDs that won't fit on the boat.

Yeah, the wiring on ours is much the same; stuff that would make a British Leyland employee wince. It's all going away and being replaced with new, proper wiring and blocks.

And I still work in electronics repair and calibrations; smoke is bad. But it's also a good indicator of Murphy's location.
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