I have been reading on these inverters. They will parallel with your shore power or generator and boost if necessary.
They are not cheep Marysville list price is $2400 for 3000 Watt.
http://www.marysvillemar...m/catalog/pg447-455.pdf
(last page Vitron Energy inverter)

I have studied the brochure very interesting.
http://www.victronenergy...tiPlus_brochure_UK2.pdf

It may be out of my budget, I may be interested when I get all the more important projects done first.

Robert,

There are three kinds of inverter that you can buy:

Square Wave output: This output is simply 120 volt dc that changes polarity 120 times a second. It works just fine in AC/DC loads such as some electric motors, heaters, and some electronics. Some loads it will blow up. You don't see these much anymore.

Modified Sine Wave output: This output is around 145 volt dc that also changes polarity 120 times a second, but is "off" for a couple of milliseconds at each change. This is much easier on motors and transformers, and will run most stuff. It may not work on sensitive loads such as audio electronics, and won't run some computer power supplies. May interfere with radios.

Sine Wave, or True Sine Wave: Same stuff as what comes out of the wall at home, a smoothly-changing voltage that peaks at almost 170 volts. It is lighter (less copper and iron) and works on anything.

An inverter/charger contains the inverter, a transfer switch, and a battery charger. This is great because you will need the switch and charger anyway. You may already have a good charger, and you might be happy with a manual switch, your choice.

You have 30 A / 3600W available through your shore-power hookup, but you may not need all that away from the dock. Every ac amp you draw costs 10 or more dc amps from the battery. Don't try to heat water or some such from your batteries!

Jeff is right about cost.

You won't often see square wave output these days, just as well. Don't buy one even if it's free.

Modified Sine Wave output has been around for a while (I designed one for use on Medevac helicopters back during the Vietnam war) and are cheap, as Jeff mentions. You can get a 3KW inverter for $200, see ebay item # 120306810733. You can get a 3KW inverter/charger for less than $900, see ebay item # 220341088087.

Sine Wave inverters are newer and more expensive. A good 3kw inverter/charger, Xantrex's newest, can be had for $1700 or so, see ebay item # 270228321887, and an AIMS brand inverter-only for less than $900.

Fastjeff seems happy with a modified sinewave unit, and I don't think I would spend the money on pure sine wave unless you needed to run a plasma TV or some other fussy load. Even electric burners with electronic control seem to be happy with the modified sine wave.

Robert,

The system they have for load management is neat, but there are other ways to skin that cat.

If you look at the schematics for my 32', you will see that I have a dc generator that charges the batteries using a small diesel. There is no current regulation, except by adjusting the fuel lever to give approximately the correct charging current. The unit cycles on and off according to the battery voltage. At 100 amps or so output, there is nowhere near enough to drive a 3kw inverter, so any shortfall comes from the battery automatically.

I have used this concept in a number of home power installations and it works well. It is a lot easier than trying to regulate the voltage and current out of a generator, and is particularly suited to multiple sources of dc power.

A 3kw inverter would be good on a Marinette because that is nearly what you get from shore power. You wouldn't have to change much, but it would make sense to turn off the hot water heater since it will drain a battery in no time.

The load management system for limiting shore power is neat, but do you really need more than 30 amps? When I am using both burners on the stove (a kw each) AND the microwave, I turn off the water heater to prevent pulling a breaker. My peak use, meals, is so brief that it doesn't matter.

Without air conditioning, it is kind of hard to use up the 30 amps. My place in Florida was wired back before WWII and it had only 60 amp service, which ran my shop too.....

Doug

Jimski, The size (output) of the inverter depends on how much load you are going to run on it. Different TV's or computers will need different amounts of wattage.

I use this...

http://www.denlorstools....r_inverter_-_dc_to.html
I didnt buy it from here, I got mine at WALMART but this is the same one that I have and I paid less than $60 for it, so look around.

This will power my TV (19 inch Toshiba LCD Flatscreen with a DVD player built in) for several evenings in a row with a DVD playing no problem. Gotta keep the kids happy. It has powered my Laptop (17 inch HP Pavilion Widescreen) for several hours with no problem. I have done this with a dedicated battery for the inverter without any charger or engine running. I have even had it power my fridge (OLD MONTGOMERY WARD Apartment size) my toaster and or the coffee maker (one at a time) but I did have the engine running for all of those. My boat does have a generator but it has some serious issues and this was my work around so that I could enjoy the season while I FIX the genny.

Hope this helps you decide what to do.

Bill

My inverter will successfully run the TV, VCR, microwave, and power tools. But it will not run this weirdo fan the wife bought that has a t-stat built in. It just buzzes.

Jeff

Very interesting. It is good to know that all that stuff works on modified sine wave.

For a much better explanation of waveforms and such try the AIMS website at http://www.aimscorp.net/products.htm

My on-board TV is a radio shuck dc model with a tiny screen - good for watching the news but that's about it. I also can play movies on the laptop, but it doesn't work for a group. The stereo is a dc unit designed for cars and boats. And I have a propane grill off the transom. What I really need to run is the microwave (when I get one) and my Origo double-burner electric stove.

I have talked to Origo and they don't know a thing about inverters but tell me that their stoves are often used in RVs and so I assume it will work ok with one.

This time, I don't believe I will buy a microwave unless they tell me that it works on an inverter.

Perhaps I should just get a cheap microwave - I have seen them for $40. Not much lost if it blows up.

What I would really like to get is a microwave/oven, so that I could bake bread (at the dock only possibly because of the load) without having a separate electric oven. These are available but are not cheap yet.

"under a cabinet"? What cabinet? it seems that the last place that I have any room is the galley. I had the microwave on the counter all the way forward, but it used up most of my cooking area. My settee is a little longer than the original one, and so there is little room to put a cabinet between it and the galley. Drives me nuts.

On my last boat I simply used electric frypans and a toaster oven in place of a stovetop, and put them away when not in use. But I can't do that easily with a microwave, and even less so with the microwave/toaster/convection oven that I really want.

I agree that resistance loads will draw the same power from a modified sine wave as from a true sine wave. But my Origo E200 electric stove has some sort of electronic control and radiant heat coming up thru the glass. I still don't know for sure that it is ok, and it is pretty expensive to replace.

I don't remember the make and model of the microwave, since I had used it at home for several years before taking it to the boat. I might have logged it, but the log is on board and I'm up here in dc. Given the good experience others have had, I should perhaps just get another one. I believe it uses less power to heat water in the microwave than on the stove, although I am not sure. The radiant heat thing is pretty good about heating just the pan.

Doug,
Here is a picture of CJ in the galley, also shows what I'm calling a toaster oven & it's location. We also have the glass stove top, might be a little of it showing in lower left of picture.

Roger