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Old 07-31-2021, 10:51 AM   #1
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Harbor Freight Inverter

Hello!
I have a 1998 Mainship Pilot 30 with no AC electric except shore power. We keep her in front of our house on a freshwater lake with very little likelihood of ever seeing salt on our watch. We have a reverse cycle air, two burner cooktop, and water heater (with an exchanger that uses engine heat) that are all AC. I would like to add an inverter but the cost of marine inverters are a little out off reach for now. Has anyone used a Harbor Freight inverter in their boat? (and yes, I am usually the one that nay-says non marine parts in boats) Any opinions?

Thanks in advance…
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Old 07-31-2021, 10:58 AM   #2
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A non marine inverter to run a TV or a blender is one thing. Wiring an inverter into the boat’s system is another. You should be well versed on fresh water electrocution first.
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Old 07-31-2021, 11:20 AM   #3
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Originally Posted by tiltrider1 View Post
A non marine inverter to run a TV or a blender is one thing. Wiring an inverter into the boat’s system is another. You should be well versed on fresh water electrocution first.
Good thought!
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Old 07-31-2021, 12:21 PM   #4
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It is never possible to remove the non marine equipment after the problem and before the insurance investigation if you want to make a claim.
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Old 07-31-2021, 02:41 PM   #5
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To do what? Just a small inverter to run a few things, or a full inverter charger to run the entire AC loads off the AC Panel?

Most inverters these days are made for RV and off grid solar matkets, not specifically marine which is a relatively small market. So no fear of marine upcharge (which I believe to be over stated, but another topic)

PSW inverters from GoPower and Wagan are reasonably priced and are rated to provide 100% of their states output continuously for 24 hours, an impressive test. Avoid Renogy products for anything as they have zero customer support and are difficult to work with if a return is needed

Finally, I'd add that there is considerable expense when installing an inverter the first time due to cabling, fittings, circuit protection, meter/control, etc. Costs as much to install a cheap Harbor Freight as it does a top quality Magnum, Victron, etc.

Good luck.

Peter
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Old 07-31-2021, 05:00 PM   #6
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Finally, I'd add that there is considerable expense when installing an inverter the first time due to cabling, fittings, circuit protection, meter/control, etc. Costs as much to install a cheap Harbor Freight as it does a top quality Magnum, Victron, etc.
I'll pile on to Peter's good points. When you start using the inverter you're likely going to quickly find that your storage (batteries) and OEM generator are not up to the task of providing all that power that you thought you'd get from the inverter.

Running the air, stove or water heater off an inverter is likely a non-starter without some serious spend.

Trying to be helpful here. I see people put in new 1500+ w inverters without considering the power needs and it usually doesn't end well. If you're just looking to power a laptop or small TV a high quality 300w unit is cheap to buy and cheap to properly wire to one or two dedicated receptacles, and won't run your batteries flat in an hour.
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Old 07-31-2021, 06:42 PM   #7
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All good points to ponder…

No onboard genset, it probably would cost what I paid for the boat to install


Thus the inverter question in the first place. 3000 watt Chineesium inverter is $350. I am a talented land electrician, and mechanic. I will have the aid of a first rate professional marine mechanic. I was considering wiring it to the shore power circuit. Would probably not need the water heater portion as no long anchorages are planned and the engine heat gets it HOT. Mostly I will need short runs on the stove top and my CPAP machine. Judicious power management should handle that. HOWEVER, the insurance question does give pause…

BTW… Thanks for the input!!!
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Old 07-31-2021, 06:59 PM   #8
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A. must have healthy batteries to support your inverter.
B. Check the capacity of engine alternator
C. 1800 to 2000 watt inverter (maybe less if you promise not to use the
microwave oven on the inverter.)
D. An extra amp meter located in the area of the greatest draw on the inverter
so you overload the turn to boat off.
E. Dont plan running the reverse cycle A/C on the inverter.
F. I doubt if you will be able to use the the electric stove, away from the dock
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Old 07-31-2021, 07:18 PM   #9
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3000 watts is 300 amps DC current at 10v. Start sizing the wiring requirements for that, and the battery bank you need to supply that current.

Most folks who want a cheap easy solution get a portable gas generator and run it on the swim platform or in the dinghy. Or in my parts they run them in the bushes next to the dock with a long cord.
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Old 07-31-2021, 08:20 PM   #10
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Read your insurance policy or call them.

Never had a policy that said all appliances needed to be marine grade.

The wiring should meet ABYC for a few reasons if you care... even then, policies cover you for a lot of things they probably wish they didn't have to.
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Old 07-31-2021, 08:43 PM   #11
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Originally Posted by Fr8dog61 View Post
All good points to ponder…

No onboard genset, it probably would cost what I paid for the boat to install


Thus the inverter question in the first place. 3000 watt Chineesium inverter is $350. I am a talented land electrician, and mechanic. I will have the aid of a first rate professional marine mechanic. I was considering wiring it to the shore power circuit. Would probably not need the water heater portion as no long anchorages are planned and the engine heat gets it HOT. Mostly I will need short runs on the stove top and my CPAP machine. Judicious power management should handle that. HOWEVER, the insurance question does give pause…

BTW… Thanks for the input!!!
\
I went the exact same route as you are thinking about taking and bought a $300 Chinese 3kw sinewave inverter. First, I had it wired into my ships AC system to power the whole boat. No matter what I did, it wouldn't correctly feed the circuits. Even with the breakers off, it would backfeed and light the indicators on the breakers. The battery charger would come on with the breaker off while the inverter was on. I gave up trying to feed the ships panel with the inverter and simply ran a line directly to a designated receptacle for the microwave. It does ok but it's is definitely NOT a sinewave inverter. The microwave sounds like it's being smacked with a hammer 60 times per second and after running it for 3 minutes, it get's hot and shuts off (the microwave while on inverter power). I'm going to pull the POS inverter out before we head South this fall and replace it with a true sinewave Samlex 2000W.
If you want my 3kW POS inverter, you can have it for free. That's how serious I am when I ask you to not waste your time & money on a cheap inverter and to go with a better quality sinewave unit. You'll be much happier.
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Old 07-31-2021, 09:18 PM   #12
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In the past I have purchased some tools from Harbor Freight that I considered one time use tools. For the most part they sell a lot of cheaply made Chinese quality stuff. Any inverter they sell will not be the quality I would buy for a boat.
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Old 07-31-2021, 09:25 PM   #13
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In the past I have purchased some tools from Harbor Freight that I considered one time use tools. For the most part they sell a lot of cheaply made Chinese quality stuff. Any inverter they sell will not be the quality I would buy for a boat.

Agreed, very true. Harbor Freight is the place to go if you need a dolly or such, not for electronics.
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Old 07-31-2021, 09:47 PM   #14
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I'd just like to reinforce a point made earlier. For many low draw things a point-of-use inverter may be fine. Or, maybe a one-circuit/one-outlet solution.

A good number of people use a point-of-use inverter for their refrigerator vs buying a marine unit.

I have a kiosk touchscreen attached to a mini-PC to run OpenCPN on the flybridge. The screen is 12v. The PC runs off of a point of use inverter that gets power off of its own 12v circuit right there.

I do have a proper 2000w marine inverter and house bank, and proper marine 50A genset. And, for my style of boating, I wouldn't be without them. But a lot of folks don't need or want that.

And, even with that, sometimes people want something to be 12v. I wanted that plotter to be off the 12v circuit so it works even without the genset or inverter. I do have a simrad up there, too. But in the event I lose 120v, I'd like to keep both of the plotters running as it gives me my preferred presentation of navigation information.
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Old 07-31-2021, 09:55 PM   #15
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Many additional thoughts here.

First, don't be seduced by 3kw number. Without sufficient battery capacity, you can't draw that without issues. And most inverters have surge capacity of 50%-100% over. You really should size cables to surge capacity, which would be massive at that power. There's a good chance a higher quality 1kw PSW inverter will perform much better snd handle your loads much better than a PoS 3kw inverter, even if it claims PSW.

Second, cheap inverters often include cables but they are woefully undersized at the higher power levels. Do NOT assume that the cables included are sufficient.

Third, when cabling, use something like the BSS chart attached. Since you're a seasoned electrician, you know it's measured as a round trip meaning if your inverter is 10 feet of cables from battery connection, you size for 20 foot circuit.

Fourth, you need to size for lower end of voltage drop (3%). There are two places where you will experience voltage drop. Cables (e.g. 3%); and at the battery posts which is not easily calculated as it varies by battery type (FLA drop a lot) and size of bank.

Fifth, if your plan is go wire into your main panel, some sort of transfer switch is needed. BSS makes a barrel switch that is made for thr purpose.

Finally, it's tempting to purchase cheap Chinese components instead of Blue Sea. Don't do it. Bad place to save a few bucks.

https://www.hodgesmarine.com/blu9009...gaAjaBEALw_wcB

3000w is a lot of power. Managing it requires some serious components. Inverter may be cheap, everything else isn't.

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Old 07-31-2021, 10:28 PM   #16
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Fresh water boat and a non-marine inverter or inverter/charger can be a deadly combination As a professional matine electrician; I would not do this job.
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Old 07-31-2021, 11:21 PM   #17
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I guess I'd like to explain some of the key concerns with non-marine inverter-chargers so that this doesn't seem like a religious issue when it is a real, physical one. And also so that one can reason about it vs treating it as superstition, which it is not.

When passing through shore power, a proper (marine) inverter should maintain neutral and ground entirely separately through the inverter (the bonding between the two is on shore), but the inverter should bond them together when it is inverting and is the source of the AC. So the inverter's transfer switch needs to make and break this bond.

Many non-marine inverters don't do this. Some even do whacky things like form the AC wave by driving both hot and neutral.
This is a real problem because it disables the safety grounding conductor and can let any metal connected to it or the chassis become hot or a current-carrying return path. That includes parts of the boat connected to the water, which means one can put current into the water, among other things.

Another problem that comes up involves the grounding. An inverter has both 12v and 120v in it. For the same amount of work, the current is 10x higher at 12v than 120v, so the wire needs to be much thicker for 12v. Unless the inverter is properly grounded, should something go wrong, DC currents can travel through thin 120v wiring. That is a big fire hazard that often is hard to get right when installing a non-marine inverter.

And, of course, non-marine devices may be more likely to corrode or otherwise fail in the moist, salty, vibration and shock-filled environment of a boat, which is bad -- and makes the problems above worse.

If the inverter is point-of use, without a transfer switch, and in no way connected to the boat's normal AC system, the risks go down a lot. Then the 120v load is just another form of work being done by the boat's DC system, not connecting to, or altering, or reconfiguring, or loading, the boat's or shore's AC wiring in any way. It is basically like a car inverter running a laptop from a cigarette lighter.

I don't want to advocate for anything here. But I do think that one can draw some distinction between a supply and distribution system and a simple load connected to one. Doing that may, or may not, lead one to think about some things differently than if that distinction is not made.
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Old 07-31-2021, 11:34 PM   #18
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Amy time you want to have a permanent install for any heating appliances (hot water, kettle, microwave, AC etc) you really don't want to be doing that off 12v and will need sizable cabling and battery bank.

Wth respect, if these are out of the budget then a cheap portable genset is the best solution. It will work the first time, no installation costs, you won't burn you boat down nor electrocute anyone.
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Old 07-31-2021, 11:48 PM   #19
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I am going to repeat what I said in post #2. Before you wire in a non marine inverter, Google fresh water electrocution. You do not want to be on the wrong side of a wrongful death lawsuit.
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Old 08-01-2021, 04:01 AM   #20
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I am going to repeat what I said in post #2. Before you wire in a non marine inverter, Google fresh water electrocution. You do not want to be on the wrong side of a wrongful death lawsuit.
Any further xomment on difference between a marine inverter and a non-marine inverter? Recommendations?
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