AC electricity
on a boat.
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This page updated: March 2010

Genset (Generator)
Inverter (DC-to-AC)
Shore Power


Ways to get high-power AC:
  • Shore-power connection.
  • High-output modified AC alternator on main engine.
  • Genset (generator set).

Genset versus Using Main Engine:
Genset better:
  • Dedicated engine is smaller than main engine, so uses less fuel, gives less noise and vibration and heat, and runs at a more efficient load point.
  • Wear and tear occurs on an engine that should be cheaper to repair/replace than main engine.
  • Running main engine at low load typical of battery-charging is damaging to main engine.
  • Having two engines gives some redundancy.
Using Main Engine better:
  • Genset is very expensive.
  • Genset takes up additional space, and adds weight (probably in a bad place, too: lazarette).
  • Genset is yet another system to maintain, stock spares for, etc.
  • Genset usually gasoline-powered, causing safety issue and requiring separate fuel tank and additional weight.
From Gary Elder:
I have seen many people install gen-sets after setting up their 12 volt systems around a big inverter and high output alternator.

Fabco Belt-Driven Generators

From Arild Jensen on The Live-Aboard List:
> My new Iota 55A charger has started
> blowing polarity fuses.
> ...
> I enquired with the local Honda service facility,
> and they suggested that the inverter technology might
> be the reason for the open ground.

Inverters generally have a situation with "open grounds" unless they are wired according to ABYC standards. This is the big factor that distinguishes "marine" from other use inverters.

A normal non-marine inverter has a floating output; meaning neither line is connected to ground. Marine applications require the AC system to be "polarized" and the designated neutral must be tied to ground.

In the case of a portable Honda genset this is not feasible for obvious reasons. However as soon as you connect it to a boat system you end up with problems (one more reason why the use of portable gensets is discouraged on boats). Your IOTA charger evidently looks for a potential between the green ground lead and the negative output lead. I haven't seen a schematic so have to make an educated guess.

The solution is to have a ground connection from your white wire neutral on the genset to your vessel AC grounding bus.

However when you connect to shore you MUST disconnect this ground strap or risk accelerated corrosion due to galvanic or stray currents circulating through the shore power cord.

I do not know if connecting such a ground strap on your Honda EU generator wil create any effects or problems for the Honda safety circuits or self protection scheme.

If you never connect to shore power this may not be a problem.
From Lew Hodgett on The Live-Aboard List:
Another fine example of why an isolation transformer should be installed.

Genset (Generator)

From Karl Denninger on The Live-Aboard List 12/2002:
Re: Genset recommendations:

I went through this last year.

Gig had an old 8 kw Onan that had an electrical end go out - I could have had it rewound for about $3,000 or so, all-up, but then I'd still have a tired and loud engine. She was burning a good bit of oil and while it was able to produce full power, it was loud and just plain ill-mannered.

I looked at Westerbeke, Northern Lights, Onan's current line, Panda and Kohler.

The Kohler won.

A year later now I am completely happy. It's QUIET - in fact, much quieter without a sound-shield (I didn't buy one) than my old Onan was WITH the sound-box! I can BARELY hear it over the AC circulating fan in the master stateroom (adjacent to the engine room) and can't hear it at all from the guest (forward) berth.

It requires no preheat and starts instantly. Even when the outside air temperature is 40 F (I haven't tried in colder outside temps yet).

It is more fuel-efficient than the old Onan, burns almost zero oil between changes, and in fact doesn't even get the oil very dark - unlike the coal-black oil that used to come out of the Onan, and DOES come out of my mains. The oil analysis reports coming back on it is so clean I wonder if it's a gas engine down there sometimes!

The engine is a 3-cylinder Yanmar and sounds like a sewing machine when it's running from the cockpit.

The best part? It was no more expensive than the 'Beke or Northern Lights (in fact a bit cheaper than those two), was a LOT cheaper than the Panda (like less than HALF as much!) and has the best warranty (5 years or 2,000 hours in recreational service, INCLUDING labor to remove and replace) of any of them.

Panda claims to have the "best warranty in the business."

Horsecrap - Kohler beats them hands-down on that account.

If I was doing it over I'd buy the Kohler again in a second.

I am completely satisfied with my purchase, and have over 350 hours on its clock thus far.

From Margaret Pittelkow:
I have had 2 Kohler gen sets, both nothing but problems.

I am on my second Kohler 5.E generator. The original 1999 generator had numerous issues and was eventually replaced in January of 2001. Not by Kohler.

The second generator has followed the same path. Since its installation I have had numerous issues ranging from bad sensors, to having to replace the carburetor and starter. After logging more repair hours than running hours, the repair shop stated that it appeared that the generator was taking in water. They had found small amount of water in the oil. The Original generator had a siphon break; when the new Gen Set was installed a siphon break was not included as it should have been. The repair shop also found a faulty Factory Kohler fuel filter, As a result of these findings I had the Factory Kohler fuel filter replaced, added a second heavy-duty filter, and a siphon break. Kohler and TAW refused to cover these repairs although the installation repairs had been performed by the Kohler Certified shops and Techs they had specified. Kohler and TAW maintained that although they dictate the shops and techs that may install and repair the generator to maintain the warranty, they take no responsibility for the work these shops perform.

The generator has again ingested water. This time water was found in the oil and in the cylinders. Kohler and TAW stated that they will not look into the cause of the water entry to determine if they will cover it. In addition, they have taken the position that the water ingestion has voided my remaining warranty and no future repairs of any kind will be covered regardless of the cause.

Upon investigation of this issue I find that my case is not isolated. Another boater in our marina has recently experience the identical situation. In both cases our generators were running under load with no problems. Less than 24 hours later the boats having never left the slip, the generators had hydro locked and would not crank. In his case Kohler and TAW have taken the same position, they would not look into the cause and the water ingestion has voided any remaining warranty.

I am now trying to get whatever life I can out of the Gen Set before I have to replace it. I have removed the water begun repairs. In my search for parts I found several repair shops listed as Kohler certified shops that had also experienced problems.

One simply suggested I replace the Kohler system with another brand, stating he would never put a Kohler on his boat; another stated that due to problems he no longer carried Kohler products.

One shop went as far as responding to my inquiry by sending the following e-mail response:

"If everything you describe is correct, then the unit is installed correctly. The problem is probably in the genset. One of the reasons we dropped the line in the late 90s was they were having some problems with the small gas units and not telling the dealers about it. (I had to find out from my Westerbeke rep.) After being threatened by several customers of lawsuits due to their units not being operational and the Kohler rep telling me to let them sue, I decided I didn't need to be in that picture anymore."

Kohler's attitude expressed above, let them sue, is exactly what several others I've spoken with and I have experienced.

An offer was made to replace my engine, labor at my expense, with an engine having more hours on it than my existing engine. They would provide no explanation as to why it had been removed from another generator, nor warranty. In an earlier conversation I had asked them to cover a $200 invoice from a repair shop and they refused. I suspect the fact that they offered this engine, but refused to pay the $200 invoice is a true reflection of the engines value.

I was recently on a weekend outing, 4 boats with Kohler gen sets, by Sunday morning none of the 4 were running, 100% failure rate.

I was recently looking into a boat for sale at a nearby marina, again more stories of problems. The current owner stated that he has had problems with the generator and kohler has not been responsive.

I have found that Kohler Power Systems is neither willing to back up their product, or take responsibility for the certified shops and techs they dictate must be used to maintain the warranty.

From Norm on The Live-Aboard List:
Diesel generators:

The Panda is the quietest because they have the unit TOTALLY enclosed in a sound box. But they run seawater through the aluminum generator end to do it. The guys at the booth at Annapolis say it's all right, it will take a long time for the aluminum to corrode. I don't believe them. The corrosion will form a crusty heat-insulating barrier between the aluminum and the water and eventually plug up the passages. If they had used a heat exchanger they might have something.

I have a Northern Lights 8 KW which engine and generator are made in Japan. Alaska Diesel likes to brag a lot about their gear. Don't believe them. It is a good rig but needs work before it is satisfactory, such as: engine-side stop/start controls, output breaker, local outlets, engine-side oil pressure and temperature gauges, 120 deg shutdown "clixon" switch on rubber exhaust hose (available at HVAC store, it has saved me from replacing that hose a dozen times), shield (I use duct tape, but a stainless shroud would be nice) around seawater pump shaft area to prevent spraying seawater into alternator when pump seal fails, strainer on hose output of seawater pump (I used a little plastic one designed to protect the potable water pump) to catch rubber bits, indicating breakdown of impeller and to prevent fouling of heat exchanger, etc., and in my case at least, installation of pre-start lube oil pump. It would also be a good idea to junk the $165 toy alternator that comes with the machine and replace it with a run-of-the-mill $45 Delco. You would have to make a new bracket but you will get twice the output at a quarter of the cost and ready availability. Another thing, the cast iron exhaust elbow rotted out after a few years. I had to make a stainless one. Get a stainless one right away while it is easy to install. There is something that rattles inside the generator end when I shut the machine down sometimes. I don't have a clue and neither does my dealer. So far, the machine runs OK, but it does make me a little uncomfortable.

While some folks have had good experiences with Onan, most have not. They seem prone to breakdowns, especially when not run often, and the parts are extremely expensive.

While a genset is great to make lots to electricity, I recommend against relying on it for basic needs. There are some boats that are totally electric, electric galleys, heads, hot water, ventilation, windlass, etc. When the genset goes down, and it will sooner or later, the boat is unlivable.

From article by Ed Sherman in 10/2002 issue of Cruising World magazine:
Diesel gensets ranging from 5 to 6 KW, list prices range from $5K to $11K.

Portable gas generator:
From Jim McCorison on Latitudes and Attitudes Cruisers Forum:
I would strongly recommend against a portable gas generator on a boat. Yes, I know people use them. But friends of ours almost got killed by one. They kept it in the aft lazerette and when they used it they ran a flexible duct hose for the exhaust up and overboard leaving the lazerette cover open. Later in the evening the wind blew it closed pinching off the exhaust hose. Fortunately they couldn't figure out why their 8 year old granddaughter was acting drunk and went to investigate. Two people ok after a few hours in the hospital, the other was ok after a 24 hour stay in an oxygen tent.

The other major problem is that if you have diesels you probably aren't in the habit, or aren't equipped, to run bilge blowers. Therfore it shouldn't be kept or run below decks.

Of course you could always run it up on deck. But the damn things are so loud you'll probably have half the anchorage offering to perform a buoyancy test on it.

If you really need a generator it is best to bite the bullet and get a proper marine one with a proper installation. The alternative could wind up being far more expensive than you planned.

From Bob Bitchin on Latitudes and Attitudes Cruisers Forum:
... I always carry a small gas (usually a Honda) backup generator. I assume I will be smart enough to run it on deck, in the open, and won't suck on the exhaust pipe (except for an occasional high!). I have an 8KW Fischer-Panda diesel generator installed belowdecks, and I love the damn thing. Quiet, vibration free, but it cost a little more than the "standard" Northern Lights or Onan. Why? Because it is a new technology. I don't want to bore you with technical sh*t, but basicly, instead of having mass quantities of heavy copper wire spinning around, it uses a small stator, and the electrical end is water-cooled, cutting down vibration and heat. It only comes with a sound shield (not as an option) and, since it is water-cooled completely, it doesn't overheat, as others tend to do when enclosed. As for the price, I gotta be honest. I don't know. They advertise with me and gave me a hell of a discount. However, in all fairness, so do the other manufacturers, so I could have chosen any one of them (as can you). I think it runs about $10-11 grand.

Something to keep in mind when choosing a generator. If it's your primary, buy one that uses the same fuel as your engine. Diesel is best. Be sure you calculate all your needs (i.e. water heater, charger, vacuum, toaster, air conditioning (hey, it could happen!) and watermaker). Choose one that will fit the area that you will be installing it. If you are going cruising, ask the factory for a "spares kit" and be sure to take it with you.

From Greg the Great on Latitudes and Attitudes Cruisers Forum:
A lot of people carry a small backup generator not for running all night, but to use as a backup battery charger or for electric tools.

From Ed Kelly on The Live-Aboard List:
I would forget about any contractor-grade generators or the cheap noisy ones.

Your reference to the Honda generators is on the right track if you are interested in a portable that is quiet. They have 3 portable models that are certified as computer-friendly, as they filter through an inverter and have very low decible ratings. 67 dB which you quote must be another commercial unit and is not nearly as quiet as the portables I am referring to. (67 is just below the threshold of a vacuum cleaner which is around 70 dB).

I have considered them, only because they can be used on the hard and are so portable. I can forsee emergencies where one could be handy.

The three rated as having smooth sine waves and being computer friendly are:

EU1000iA2 1000 Watt max (900 W rated) 59 dB at full rated load - 30 lbs $780

EU2000i 2000 Watts (1600 W rated) 59 dB at full rated load - 48 lbs $1000

EU3000is 3000 Watt (2800 W rated) 58 dB at full rated load - 134 lbs $? (per our Northern Hydraulics store)

They can each be cabled together with a combiner to double their output.

Downside is the fact they use gasoline (but are very portable in a small unit). The output in the DC side on both is 12V, 96W (8A), but their AC is a lot higher.

From Troels Kirk on The Live-Aboard List:
We've owned a Honda Eu100 1000W for a year and a half. Size and weight is perfect for our smallish catamaran. It's mainly used for supplementing the solar panels when coping with grey/wintery skies.

It has proven to be totally reliable, relatively quiet at it's lower speed, and easy to maintain. If stored inside, it's easy to empty the tank, and there's a smart way provided to empty the carburetor as well. When on low power (under 500 W or so) it seems to run forever on a couple of liters of gasoline.

Highly recommended!

From Bob Austin on BoaterEd:
> I have heard great things about Honda's EU2000
> but see that the price is listed at over $1,000.
> Today at Home Depot I saw a Coleman 1,850 watt
> generator for $399. Is there really that much of
> a difference between Honda and the other generators?

There is a world of difference and the Honda is definitely worth the cost. The Honda is many magnitudes quieter and with less vibration. The components will last much longer (I have a smaller Honda which is 30 years old and still runs fine). The Honda is an alternator inveter which will synchronize with other Hondas, so that if necessary you can put two EU 2000's or with a 3000 or 1000 for more power. The Honda is lighter.

Do not anchor in a cove where I am with the Coleman!

From Flying Pig on list from
... my on-air seminar on the Honda eu2000i generators so popular among cruisers, but bedeviled by what I can only assume is a make-standard-parts-fit-non-standard-applications policy at Honda which has nearly every 2000 eventually break their starter pull-cord due to a non-fair exit in the rewind mechanism. Fixing that (well, making do on a relatively permanent basis - there's no fix without boring into the crankcase and relocating the mounting bolts) is very simple, but getting to the part isn't! As I'd done a great deal of phoning around to distributors, I eventually was able to find a service company who had a tech willing to walk me through the procedure, which I shared. It's tedious, but not difficult.

That on-air session also included many tweaks I'd learned from the Honda2000 mailing list on yahoogroups. Fortunately for those who came last year and took notes, even though they'd not yet had the problem, they (as several ashore had told me) were able to repair their broken cords successfully.

[S/V Freedom's "Replacing a Starting Cord in the Honda 2000i Generator".]

Someone suggested putting the gas genset in the dinghy and running it there, with the AC cable coming onto the boat and plugging into the shore power connector. That way, noise, vibration and exhaust are off the boat. Of course, an AC power cord over water is not a happy thing, a fire would kill both generator and dinghy, and a big wake could cause a problem.

From Laurie on Cruising World message board:
Don't buy an AC generator. Get a diesel driven alternator and inverter. It's much more efficient to charge batteries with an alternator and use an inverter, than to have half of your A/C KW rating just rattling around doing nothing (or being 50% efficient running a charger).

Ample makes a 150 amp alternators driven by small Kubota diesels. IMO they're the best on the market and go for about $4,000. With a thousand watt inverter and installation you're looking close to $6,000.

But it's the best way to go by far. You'll be glad you did for more reasons than I can explain right now. ...

I can sell you one at a great deal.
More from Laurie on Cruising World message board 12/2000:
... DC generation has always been much better for battery charging, and inverters now can easily handle any large load. Couple this with a larger battery bank and you get the easiest to manage power utility that you can operate.

When you expect high loads, run the alternator gen-set. It will carry the entire inverter load, then shunt all extra amps into the batteries. When the inverter load drops, the alternator stays running, but more amps go to batteries. Very efficient. When you expect light loads or value silence just use the batteries.

The clincher here is convenience. Once you live with the system you would see it's much easier to run than adding an entire new power generation scheme into your utility, with complicated switching for startup use, relying on separate AC chargers/regulators for battery charging, etc.

Inverters give their full-rated power whenever you need it instantly and silently -- with much more ready at the flick of a switch by starting the diesel alternator. And by upgrading batteries, you'll get more efficiency and more generator "off time" with AC still available.

IMO Ample Power has got the best diesel driven alternators on the market. You can get a macho 180 amp alternator matched to a Kubota diesel with a high performance regulator for about $4,000. Better yet, each component is feasibly field replaceable (not so with many ac gensets), so if you have trouble Ample can send new regulator, or a new alternator (and the Kubota is reliable). Basically, it's a three-component plug and play system that's easy to service with spare parts that are easily stocked (like a spare alternator that fits both the boat and the DC genset).

I was so impressed with the numbers and Ample Power's experience on this I became a dealer. ...

From Matt on Cruising World message board:
Check out the Balmar DC genset. Interesting combo with the 250 amp DC alternator, 3000 watt inverter, water maker and dive compressor unit, a lot of bang for the buck.

From Norm on The Live-Aboard List:
I have a Northern Lights genset. Some things I did to it when I installed it:

Local pushbuttons to prime, start, and stop the unit from engine-side.

Local oil pressure and temperature gauges on the engine.

An ammeter to check on the starting battery charging alternator.

A freq meter to adjust the governor.

An engine hour meter to know when to change the oil (a MUST!).

Circuit Breaker on the output line. There were already circuit breakers on the field and 12 VDC circuits.

120 and 240 vac outlets on the unit itself so I could have power even if the ship's distribution system was compromised.

The above electrical items were all mounted on the control box that houses the control relays and voltage regulator.

A 120 deg F, Klixon, normally open thermoswitch (available at Grainger) on the exhaust hose (held on with a spring around the hose) wired to shut down the unit if the hose gets hot above 120 deg F (indicating a seawater flow failure). The engine block will not get hot enough fast enough to shut down the unit before damage to the exhaust hose happens if seawater is suddenly cut off as by a plastic bag, etc. This has saved me several times.

A pre-start lube oil pressure pump to pump up the lube oil pressure in the engine when you press the "prime" button. This is a 12 VDC gear pump I bought from Depco. "They say" 80% of the wear happens in the first few seconds of operation due to dry bearings.

A ball valve and piping to drain the oil easily for oil changes (every 200 hours).

A compound fuel pressure gauge downstream of the secondary (engine mounted) filter to tell how plugged the secondary filter is.

I would like to have:

The oil filter to screw "up" instead of "sideways" so the oil wouldn't make such a mess when I change the filter.

A little funnel and tube to carry away to the bilge the seawater leakage from the mechanical seal on the seawater pump. These seals, on the main engine too, always seem to leak somewhat. Even when I replace them, sooner or later they leak again, but small leaks. Until they get substantial, I prefer to let them leak but carry the drippings away with a funnel and tube to keep the nearby metal from rusting.

As for your relay. This is common in stand-by power systems ashore and is called a "transfer relay" to transfer the load from the mains to the generator. Personally, except for protective devices, I shy away from automatic things in general because I want to be fully aware of what is going on. I have is a rotary manual transfer switch with "shore power", "25 KW", "8 KW", and "grounded" positions. Before I move the switch I strip all loads via the circuit breaker panel. This protects the transfer switch from arcing and also starts the new power source with no loads. I then re-apply the loads.

Another consideration comes into play if you have an inverter. My Trace synchronizes itself to the external power source when one is available and actually aids the external source for short heavy loads such as motor starting. I quote:

"External Transfer Relays"

It is not acceptable to switch the AC input from one AC source to another while the inverter is connected. This applies whether the inverter is in battery charging mode or inverter mode. Switching the AC input from one source to another can result in a loss of synchronization that can cause a severe overcurrent condition that is far worse than short circuiting the inverter. Two separate AC inputs are provided to eliminate the need for use of external transfer relays. If a transfer relay is used, it must provide a center "off" position that causes a loss of input power to the inverter for a period of at least 100 milliseconds. This will allow the inverter to disconnect from the original AC input and then re-synchronize to the new AC source even thought the same AC input terminal is being used. During the transition period, the inverter will have to operate the load while it re-synchronizes to the new AC source (about a thirty-second period at the minimum). Most transfer relays will switch too fast for the inverter to detect - and will cause the inverter to lose synchronization with the AC source. This is indicated by the inverter shutting down upon transfer and the red overcurrent LED indicator flashing or turning on.

Manual, hand operated transfer switches may be acceptable since the transfer time can be slow enough for the inverter to detect. The switch must go through a center "off" position. They are often used to switch from one generator to another. Since the inverter has a separate AC input for a utility grid, a transfer switch is not required to switch from the utility grid to a back-up generator. The inverter will not allow the generator to be connected to the utility - if both are available, the generator will be disconnected and the inverter will be connect to the utility on AC INPUT 1."

I cannot find it right now but I remember a passage in the manual that cautions against connecting the output of the inverter to the AC mains. I recall that it said the damage resulting from such a connection is "massive and obvious and NOT covered under the warranty". I have a friend who did just that twice and the damage was "massive and obvious and NOT covered under the warranty".
From John / Truelove on The Live-Aboard List:
> "They say" 80% of the wear happens in the first
> few seconds of operation due to dry bearings.

Yes, they do, and yes it does. But it isn't due to "dry bearings." It's due to metal-to-metal contact between bearing surfaces before the hydrodynamic "wedge" develops. The wedge is developed by virtue of the bearing surfaces moving in relation to each other. It is not developed by pressurizing the lubeoil system prior to start, and the same amount of wear will occur during starting whether there is pressurized oil at the bearing journals or not. Prelube pumps are a good idea on large engines which require a lot of time to fill their oil distribution and filtration systems, and also on infrequently-run engines such as those powering standby generators. They are a waste of money on small, frequently-operated Diesels.

Inverter (DC-to-AC)

SailNet - Tom Wood's "110 Volts On Board"
SailNet - Don Casey's "Inverter Realities"
West Marine's "Selecting a Power Inverter"
BoatU.S.'s "Inverters"
Inverters articles in 5/2001 and 6/2001 issues of Southwinds magazine

Types of AC output:
  • Square wave.
  • True sine wave.
  • Modified sine wave. (More like a square wave.)
Conversion to true sine wave is 5% to 10% less efficient than conversion to modified sine wave.

Want true sine wave; modified sine wave affects some clocks and radios and a few rechargable battery chargers, and "contains harmonics that cause additional heating in motors and transformers".

Laser printers require true sine wave power.

From BobG on Cruising World message board:
Don't overlook the sine wave. We made that mistake when we bought a 1500 watt inverter. Later we discovered that so many electrical things require a full sine wave. Anything that uses an electronic chip for timing requires a full sine wave. IMHO the larger unit with full sine wave is a better choice, if you can afford it.

From Norm on The Live-Aboard List:
The term "modified sine wave" is a salesman's lie. The output is a square wave. Many loads don't mind, but some do and the output tends to be noisy because of the abrupt changes in voltage.

The term "pure sine wave" is also a salesman's lie. The actual output is a stepped waveform resembling a stepped pyramid. The number of steps depends on the design and the load. That being said, the resemblance to a sine wave is enough for almost all loads to act as if is were actually a sine wave.

As far as I know only a very expensive style of inverter will output a true sine wave. Also a motor/generator set will. Both of these have poor efficiency and are not useful to us.
From Arild on The Live-Aboard List:
Norm is right about "modified sine wave":
MSW originally meant Modified Square Wave because the second generation had a couple of steps in the square wave output.

About "pure sine wave":
We used an oscilloscope to compare the Trace and Statpower inverters. The Trace SW2512 had 72 discernible steps in each cycle. The high-frequency switch-mode designs from Statpower had 4000 steps in each waveform. We could not actually see individual steps but Engineering assured us that based on the switching frequency there should be 4000. On the scope the output looked as good as the pure sine wave coming from utility power.

From Pascal on BoaterEd:
You don't need a true sine inverter for TVs. The only things which do not work (and burn up) on MSW are tool chargers. Cell phone, MP3, computer chargers work just fine ...

Types of inverter construction:
  • Line-frequency switching (older; 4x heavier; hum and noise increase as battery voltage declines).
  • High-frequency switching (newer; lighter; more complex; high-frequency noise may affect SSB and weatherfax).

Inverter specifications:
  • Waveform type (square, modified-sine, pure sine).
  • Idle current (current drawn from batteries when no AC load is applied).
  • Efficiency (output power / input power; varies with load).
  • Automatic transfer switch (detects presence/absence of shore power) ?
  • Includes battery-charger ?
  • Charging modes (sophistication of the battery-charging part).
  • Controls and meters.

See inverter reviews in Practical Sailor's 1999 Gear-Buying Guide.

Statpower, Trace, Heart all made by Xantrex.

From Larry DeMers on The Live-Aboard List:
I installed a Heart Marine Combi 12-15 (1500 Inverter capability) this past summer [2000]. Heart has some problems with EMI/RFI in their gear (all of their gear that has an oscillator), and the charger/inverter is no exception. You may be bothered by the 60 hz. growl radiated from the ac wiring in the boat. They do have a fix for it ... at your expense, you need to add a Corcom filter to the AC output lines, as it leaves the charger/inverter. This is a rather large device that would be better suited to be installed inside the cabinet of the charger/inverter in my opinion. It sure would make the AC wiring neater and easier to route etc.

From Norm on The Live-Aboard List:
I have a Trace SW2512: 12 VDC, 2.5 KW, $2000, "sine wave" unit. Aside from two warts (2 relay auto generator start instead of three, and volatile parameters requiring reprogramming after a 12 VDC interruption) it is a fine unit.

Be aware that the manufacturers lie about the wave form of their outputs.

"Modified Sine Wave" is the more blatant lie. The output is in fact a square wave with some off time between the pulses. Nothing remotely resembling a sine wave.

The "Sine Wave" output claimed for my Trace is in fact a stepped waveshape resembling a Mayan pyramid. The number of steps vary with the load.

The square wave output inverters are a bit more efficient than the stepped wave inverters. However, the biggest effect on efficiency is the relative size of the load.

For example, according to the graph in the manual my 2,500 watt Trace is the most efficient (about 92%) at a load of 300 watts. At very low loads the "overhead", or the power required just to run the machine, is a relatively large percentage of the power draw so the efficiency approaches zero as the load decreases. At higher loads "I squared R" losses gradually rise as the current levels increase until efficiency is about 80% at 2,500 watts, maximum rated continuous load.

From Arild Jensen on The Live-Aboard List:
Inverter manufacturers do know that "modified sine wave" inverters cause problems. This is attested to by numerous customer complaints over the years. However, customers, American customers in particular, will almost always choose price over quality. They percieve consumer products as disposable so what if it quits a little early. Toss it and get another! Time for a style change anyways, or sentiments to that effect.

Induction motors run hotter and do not last as long. Electronic controllers struggle with the steeply ramped-up voltage and soometimes fail as a result. They tend to overheat or quit altogether with what they perceive as voltage spikes.

A toaster doesn't care, so it works fine. A DC drill (universal motors) doesn't care much since it chops up the clean sine wave with its commutator. But if you pay attention, you will find that a Skilsaw or any other power tool does work faster, smoother and with more power at part speed range when run off pure sine compared to a MSW.

Switch-mode power supplies such as you see in many AC-powered electronic equipment like TV and computers do not really care either since they make hash of the sine wave.

BUT!! ... the newer generation of universal power blocks, smart fast chargers and other sophisticated products designed for a global market with varying voltages and frequencies get confused by MSW power. Result; pissed-off customers and sometimes burned equipment.

How do I know this? Because for two and a half years I was a marine applications engineer for Xantrex during the corporate merger period when Statpower, Trace and Heart got rolled into one. After the merger a lot of notes wer compared amongst the staff and all the sales bluff was swept away.

Even they realize that MSW is a dinosaur design and corporate plans are to eliminate all MSW products in about two years when the next generation of pure sine wave products are slated to hit the marketplace. They have already been all but shut out of the European market because MSW simply doesn't meet current European EMI pollution standards. Companies like Mastervolt are grabbing market share in all parts of the world becauss they already have more sine wave products and their few remaining MSW products are better filtered and shielded.

As cruising folks who live off a battery away from shore power you should care about the difference in sine wave vesus MSW. Lab tests have demonstrated that the same equipment uses less power and thus runs longer on the same battery charge when fed clean sine wave instead of MSW power. These tests were done by the equipment manufacturers, not by Xantrex, by the way.

Audiophiles who enjoy clean sound also prefer the cleaner sound in quality home entertainment equipment when fed by pure sine. Ham operators will attest to the amount of radiated hash in their equipment and SSB radios. The downside of MSW is considerable.
From Jim and Tom on The Live-Aboard List:
We have run extensive tests of modified sine wave vs pure sine wave inverters -- specifically the Prosine. There is no question that the PURE sine wave inverter is far superior. Just the interference to radio on the SSB VHF frequencies generated by the modified sine wave inverters is reason enough to go with the pure sine wave version. Lab tests we have conducted show a serious potential safety problem with the modified sine wave. Don't take the chance!
From Arild Jensen on The Live-Aboard List:
It isn't just inverters that produce poor quality waveforms. The new generation of small gensets have opted for a hybrid design in order to save weight.

Instead of having a massive iron core and copper-wound alternator, they employ a variety of designs including a cheap two-pole generator which then feeds power into a solid state inverter. Saving on copper and iron saves weight, reduces power requirements, and makes it easier to vibration-mount the unit. But the trade-off is poor waveform control. One of the drawbacks of some older designs was the voltage regulation. SCR controllers were notorious for generating spikes. Although the frequency was fairly close, the voltage would sag as the loading increased. Sometimes it sagged too much during a high-current start.

Cost is everything so many gensets designed for a price instead of quality, use cheap methods to regulate and control their gensets. You the consumer, pay the eventual cost, but by then the warranty has long expired, and hopefully no one realizes why appliances do not last as long.

It takes a sophisticated power-factor-corrected charger to make best use of such poor quality power. Lacking a power-factor-corrected charger, your genset run time will be longer to charge the battery up. A basic transformer-type charger will not do this. It takes the sophisticated technology of switch-mode regulators to do this. The latest designs of inverters that produce pure sine waves possess this technology. So not only do you get superior inverter power but in the case of a combination inverter/charger you get faster, more efficient battery re-charging.

Manufacturers of the old traditional designs are dropping prices in order to clear inventories and cash in on what they perceive as the last chance to capitalize on this old technology. The leaders have already switched over. The copycats and also-rans are lagging behind. Without a solid engineering base to develop their own technology they have to wait for the next wave of products to emerge before they can copy it.

The low price of the MSW products you see in the stores right now is a clear indication that this is the end of the line for the old technology.

From Maroth de Marothy on World-Cruising mailing list:
Microwave oven ... a WARNING: if you plan to buy a new one, make sure your inverter puts out a pure sine wave, otherwise your new DIGITAL microwave won't work.

We found this out the hard way: When in Panama, we got rid of an old, non-digital microwave and bought a nice new one. Worked fine under shore power but not with inverter. This drove me nuts until someone explained the problem to me. Since I can't afford a new inverter that would create pure sine wave, the microwave is only usable when in a marina ... something we try to avoid!

From Phil Rosch on The Live-Aboard List:
[Heart Freedom] Inverter Gremlins:

It's another 90-degree day at Block Island and my Freedom 25 stopped charging and inverting. Nightmare scenario? Not so, because I learned (the hard way) the magic secret about these inverters and I'm going to share it.

1. If your symptoms include charger amps starting at 125, but then dropping to zero and starting up again over and over ...
2. If the charger and/or inverter blink off at the control panel, then resume a few seconds later ...
3. If the lights on the panel go out and stay out ...

The problem is your grounds. The may look tight, but they aren't. If you have thumbscrews holding down your negative cables, float-test them and replace them with nuts and lock washers. Clean the terminals and cable ends until they shine, then bolt them down and hose them down with corrosion-blocker.

At the first sign of any problems with your inverter, repeat this process.


There's one other measure you can take when faced with desperation, short of float-testing the entire unit. If the inverter/charger is acting strangely but doesn't have a foul smell or the look of the proverbial "smoking gun", the problem may be the microprocessor equivalent of Alzheimer's.

One example is when the control panel indicates the charger can't make up its mind what phase it is in. You might be sure you should be in the bulk phase, but the charger drives up to 125 amps, then down to zero as if it had finished the float phase. Doing this repeatedly at 3-4 minute intervals is a sure sign of corrupt memory in the unit's "confuser".

Technical bulletin issue #19 says these "brain-farts" can be caused by nearby lightning strikes, voltage surges from shore power or generators, engine starter motor related spikes and dips, or high-voltage propane igniters.

The recommended "re-boot" procedure is to remove all A/C power (un-plug and/or turn off the genset), disconnect the phone jack powering your control panel from the unit, turn off the inverter power switch if you have one, and then disconnect the negative battery terminal for a full 5 minutes. This will allow the micro-confuser to be "refreshed" at the next power-up.

Reconnect the negative cable and expect a pretty good spark as the filter capacitor charges up inside the unit, then plug in your control panel, apply power to check the charger, and then remove it to check the inverter function. If this works, pour yourself a "Dark and Stormy" and declare success.

From Arild Jensen on The Live-Aboard List:
Many Asian built-boats have the neutral white wire connected to multiple branch circuits. I have found this out the hard way. By ringing out the individual circuits at the main panel I discovered there are more black wires leaving that there are white wires returning. The reason being that the electricians tied two or more outlets together on a single common white wire. This practice can produce more electrical noise and allow any spikes to cross into multiple circuits.

While the old Heart models didn't seem to mind this too much, the new Prosine shuts down every time. The fault detection circuitry is too sophisticated and rejects the odd wiring configuration as a fault.

Another practice which can contribute to electrical noise that causes inverter memory problems, not to mention actual metering problems, has to do with separating the neutrals for the input and output circuits.

When the whole boat is wired through the inverter there is no problem. The shore power input line connects directly to the AC IN terminals. All the boats electrical panel connects to the AC OUT terminal. However, it is not a good idea to run high loads like water heaters, baseboard heaters and air conditioning through the inverter since these drastically reduce battery run time.

For such installations you should run what is called a split bus. The high draw equipment is wired to the main panel along with the inverter. The remaining loads are fed from a separate bus that is connected only to the AC OUT of the inverter. Many installers fail to separate the white neutrals as well. They leave all the neutral wires connected on the same bus bar. This forms a feedback loop where noise and voltage spikes can loop back to the input where the inverter's sensing circuits can get confused.

If the boat has been wired with multiple circuits to a single white common wire, the problems multiply. Last week I came across a boat that had been upgraded from an old Heart inverter to a new Prosine. All of the above conditions existed and naturally the inverter kept shutting down and refusing to work. While the inverter would usually work on shore power it flatly refused to work with the genset.

Careful investigation revealed that the genset had never been properly wired so the white wire was bonded to the green wire. The manufacturers do not necessarily tie the green and white wire together since many applications in metal hulls require them to be kept separate. Evidently the original installers failed to do this necessary step. The old Heart model inverter was not sophisticated enough to detect the problem. The new Prosine did and shut down. It was only a matter of luck that no one ever received a shock from this poor wiring setup.

From Ben Okopnik on The Live-Aboard List:
My 2kW inverter cost less than $90 brand new (Whistler 2000, on sale at Harbor Freight).

Just for general info, I've owned Whistler inverters of all sorts over the years, and for a dirt-cheap off-brand, I'm very impressed with them. I've only ever had one blow out - at which point, I replaced the easily accessible transistor and was powered up again within 20 minutes (something you _won't_ be able to do on a number of the high-end units.) The thing that I find really good about them is that they work *way* beyond their rated capacity, especially the small ones. I had a 600W unit on my previous boat, and it ran my little Shop-Vac vaccuum cleaner just fine; I didn't realize how amazing this was until I tried using it on several much larger inverters (up to twice that size), and none of them could handle the startup load.

The only annoying thing about them is that you "pay" about 1A @ 12VDC in standby current. I just shut mine off when I'm not using it.

Shore Power

AC outlets from different countries

West Marine's "Shore Power"
Steve Dashew's "AC Shore Power Adaptors"
120/240 shore power article in 10/1/2000 issue of Practical Sailor.
Two articles in 4/2003 issue of Cruising World magazine

From Loren Beach on Yacht-L mailing list:
This last winter we had a local surveyor give a presentation to our club members. She brought in her box of blackened shorepower connectors and blackened plugs as a sort of traveling horror show. We had heard this from another surveyor before, as well. Evidently it is common for the plug to work a little in the connector on the boat and finally start arcing over as it moves with boat movements.

I have no trouble believing this as the shorepower inlet was one of the things the surveyor found, in '94, when our '88 boat was surveyed for purchase -- it was a little blackened around where the prongs went in. It was replaced.

Definitely something to check on often any boat connected to shorepower -- just a teeny tiny bit of movement, a zillion times a day ...

From John Gill on Great-loop mailing list:
Make sure your power cord connections are clean and not worn, and inspect the dock electric station receptacles when plugging in - some are corroded and/or worn and in very bad shape. Put a can of electrical contact cleaner and an old tooth brush in your tool kit to clean them. If you can't make a good firm mechanical contact, think twice about plugging in, because you will not have a good electrical contact either!

We also learned from other boaters to take a length of 3/8 inch line about 6 feet long, make a knot around each of your power cords and then tie the cords tight against the dockside power station. This prevents accidental, vandalism or other removal of the power cord that is not intentional. More than once, we had someone try to remove one of our power cords in order to hook up theirs!

From Jeff Smith on The Live-Aboard List:
One of the most common causes of boat fires is the shore power inlet.

The connections are made with setscrews and over time they seem to loosen. I really don't know why.

As they loosen, the resistance at the connections increases, resulting in heat at the connection points. Left unchecked, a fire can result. This is especially a problem for winter liveaboards who run electric heaters and draw a lot of current.

From Lew Hodgett on the IRBS live-aboard mailing list:
[Re: Low voltage at marinas. Stimulated by a quote from ABYC:

"Marina dockside power systems may be causing problems on boats such as overheating motors and reducing the life expectancy of appliances and equipment. These problems can exist in spite of the latest and best power outlets and oversized wiring on the piers. The problems are not generally caused by the equipment on the boat or on the piers, but are due to dock receptacles being supplied with 208 volts AC power instead of 240 volts AC power."]

208Y/120/3Ph/4W/60Hz is a very efficient way of distributing 3 phase power which then can be utilized as single phase power.

The "Y" above denotes a 3 phase transformer connected in a "Y" configuration.

The 4W above describes 4 wires as follows: Phase "A", Phase "B", Phase "C", and "N" for neutral.

The voltage between any phase and neutral such as A-N is 120V/1Ph/60Hz.

The voltage between any two phases such as A-B is 208V/1Ph/60Hz.

There is no inherent phase unbalance in the above.

The problem occurs when 208V/1Ph/60Hz is used to attempt to start a 240V/1Ph/60Hz load such as an induction motor.

If you find yourself is such a situation, usually the only solution is the installation of a buck-boost transformer.

NEMA defines very specific plug and receptacle configurations for both 208V and 240V services.

If the installing contractor installs the wrong receptacles or the wrong receptacles have been specified by the system designer, that's not the problem of the distribution system.

The basic reason to use 208Y/120/3Ph/4W/60Hz distribution rather than 120/240V/1Ph/3W/60Hz is economics.

You need a lot less equipment and it is easier to balance system loading using the 208Y/120/3Ph/4W/60Hz approach.

My suggestion would be that if you have shore power installed on your boat, even if it is only a 120V/1Ph/60Hz system, include a voltmeter in your tool kit, and use it before plugging into any shore power receptacle.
From Nelson Bailey on the IRBS live-aboard mailing list:
Lew, You are dead on with the exception of the transformer being the only solution. This is a very common problem that I have found in commercial buildings that are wired with 3 phase and then had equipment installed that was wired for 240V. A large percentage of motors (such as airconditioning/refrigeration compressors) rated for 240V are also rated for 208V. It usually states on the rating plate "240/208V". It is a very simple matter of changing jumpers or connecting to a different pigtail in the endcap of the motor to change from one to the other. On a boat you just have to remember to change it back when you move to a different marina.