Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)

TorontoTim
TorontoTim Registered Users Posts: 11 ✭
in Solar Beginners Corner #1
So - I've got this off-grid cabin that's fully wired for 120v AC power. Breaker panel, the works. Currently it plugs into a 4000w generator for power (I picked up a 1000w Honda genny for more efficient use when I just need some lights etc).

Anyhow - while I sort out a small solar package, I've been playing with a 12v deep cycle boat battery I have laying about. Running some tests on it with a 200w inverter from the local auto store.

Seems plenty of juice to run a few 10w LED 120v lights in the cabin and charge cell phones for a weekend. Few hours for a couple of nights then bring the battery back to the city to charge it up for the next weekend trip.

Figured I'd just plug the whole cabin into the 200w inverter, and of course just flick on a couple lights and plug in a phone charger etc. into the wall. But even with nothing turned on, the inverter immediately registered an overload or some other fault. Red light.

I can only assume it has something to do with the sheer amount of copper wire being plugged into the inverter given it's the entire 800 sq ft cottage and breaker panel. Even though my brain tells me if there's no load on it, why would it matter, it's the only thing that changes vs. plugging a power bar into the inverter and a few items into it.

Just pulled the battery into the cottage and did that instead, plugging a floor lamp with a 10w LED bulb in it and my phone, laptop etc.

Anybody have an idea why plugging the cottage into the inverter wouldn't work? My plan was to just have a small system with a couple panels, a couple 6v batteries and maybe a 500w or so pure-sine inverter, but if it won't work with a 200w inverter, why would it work with a larger one?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    Re: Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)

    Likely a ground at the breaker box, which is normal, conflicting with the internal grounding of the inverter. You could disable the ground to check this out, or possibly use a 'cheater' to switch from a 3 prong connection to a 2 prong connection at the inverter.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    #3
    Re: Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)

    Msw inverters has a internal floating ground. If connected to a external ground (housr) it will not like it.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    Re: Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)
    Slappy wrote: »
    Msw inverters has a internal floating ground. If connected to a external ground (housr) it will not like it.

    Ditto. If you get a 300w pure sine inverter (Morningstar SureSine) that should wire into a transfer switch and your panel just fine. But the mod sine inverters
    have a "floating" output, which is usually fried with a code required grounded neutral.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #5
    Re: Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)

    Is the inverter able to run loads from the battery if they are plugged directly into the inverter? Using a set of battery clips can be unreliable... An inverter running on 12 VDC needs a fair amount of DC power--And really needs "bolted up connections" for reliable current transfer.

    Another possibility--Is the read light a Ground fault light? Some have GFI outlets already installed in the inverter.

    Is the grounded neutral at the cabin+green wire ground back to the inverter?

    And, the genset is still not plugged into the cabin when the inverter is plugged in (one pigtail to genset or AC inverter)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)

    "But even with nothing turned on, the inverter immediately registered an overload or some other fault. Red light."

    most likely, for the reasons already stated, the inverter is probably already blown out as indicated by the fault light. hope not, but the inverter may also blow out some items on charge too as some don't like a modified sine waveform, but this is becoming a more rare occurrence. even some sine wave inverters out there have the bond between neutral and ground in place already as some of these inverters weren't meant to be connected to a whole house electrical system. the ones that can often have a higher price tag too.
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  • South Africa
    South Africa Solar Expert Posts: 295 ✭✭✭
    #7
    Re: Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)

    Try this next. :-)

    Have a electrician move all the light circuits out of the distribution board onto a a plug or two, with all the safety requirements in place.

    Then connected the plug/s to a pure sine wave inverter running off batteries charged by solar array.

    Taking lights off the grid is probably the easiest thing to do, even more so if all of them are LED's.
    5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • TorontoTim
    TorontoTim Registered Users Posts: 11 ✭
    #8
    Re: Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)

    I will definitely check the whole ground thing out. It's an area that still mystifies me a bit to be honest.

    Under the cabin I see a ground wire clamped to the copper plumbing (which in itself is kind of funny given the water supply is from the lake through a PVC pipe so the copper doesn't connect to anything in the ground / city supplies). I suppose the overall mass of the copper is enough to act as a ground?

    It was something I gave some thought to but wasn't sure how this all worked and it's been on generator for 20 years working like this. The generator itself is not externally grounded - Yamaha EF4000DX and my Honda EX1000 also worked fine as-is.

    I was just trying to see if at night I could get away with plugging the entire cabin into this small battery to just run a few 10w LED bulbs in the light fixtures and keep my phones charged. After my little experiment I pulled the battery inside, clamped on the inverter and plugged a powerbar into it - worked like a charm. So the inverter isn't dead yet. It's a cheap $40 inverter - nothing special.

    So in a nutshell, in a typical smallish solar panel setup (let's say a 1000w inverter running off 2 6v Trojan T-105's with 500w of PV panels as an example), the modified sine wave inverter has the ground handled and the house it's connecting to should not have a ground wire running from the neutral of the breaker panel into the 'ground' or connected to the plumbing etc?

    And pure-sine inverters don't have this floating ground issue that MSW inverters do so they work fine? Is that a universal difference between pure and modified sine wave inverters?

    All of this was just an experiment to see how long I could last in the evenings on a single 12v boat battery, just because I had the battery handy and the inverter was $40. Bring the battery home, charge it up and take it to the cabin for the weekend sort of thing. But it's a precursor to setting up the basic solar system I described above, again mainly to handle just lights, charge phones, maybe watch a couple hours of TV on my 65w LCD tv once or twice a week - that sort of thing.

    I have no illusions of being able to run my 1/2 HP 120v water pump off solar/battery without spending a fortune. Instead for now at least I'm adding a couple pressure tanks to increase my drawdown to 30-40 gallons between pumps, allowing for most of a normal day's water use at the cottage for the three of us. So I just run the big generator once or twice a day to fill the pressure tanks and likely have showers/vacuum the cabin while it's running.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #9
    Re: Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)
    TorontoTim wrote: »
    And pure-sine inverters don't have this floating ground issue that MSW inverters do so they work fine? Is that a universal difference between pure and modified sine wave inverters?

    Almost all MSW inverters do not have an Isolated Output... Basically, if you have a ground bonded neutral on the AC output, and and a ground bonded Battery negative (or positive) bus on the DC input--It creates a short circuit across the switching transistor inside the MSW inverter.

    For TSW, almost all (all?) have an isolation transformer between the DC input and the AC output which allows you to have a ground bonded output neutral and a ground bonded DC battery bus (typically negative) and the inverter does not care.

    You need to read the manual for the inverter to be sure (or do some careful testing). If you have a MSW inverter that has been "shorted" between input and output, they appear to be just as like to smoke the MSW inverter as blowing any protective fuse/breaker.

    There are a few MSW inverters that (in their manual) do have an isolated output.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #10
    Re: Plugged off-grid cabin into small 200w inverter for fun - didn't work ;)

    A side note that its nice to see you are already using the "right tool for the job". I (and others) have been pushing the idea on this forum of using multiple gensets (and/or inverters) based on the current need. Most people just think they'll get one big genset to cover all their loads and they are done, but then wonder why it costs them $200 a day in gas. This is how Generac stays in business - sell big, or sell bigger, period. I got caught in the same trap. Thing is, you only need a few hundred watts 2/3 of the time so you end up running a big genset at its very worst efficiency for most of the time!

    By only using your smaller genset or the inverter when you don't need to run your well pump, you are way ahead of the game, congrats.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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