Surge protection for inverters

Discussion in 'Electrical Systems' started by missinginaction, Jun 13, 2009.

  1. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    As I work along on my 73 Silverton project I have time to think as I perform some of the mindless tasks (such as just spending about 10 hours over three days sanding multiple coats of who knows what kind of paint(s) off the cockpit floor and engine compartment cover. (and yes I wore a respirator!)

    I have the electrical system figured out and partially wired in at this point.

    When I get ready to launch this old boat next summer I'd like to install an inverter/charger (probably a Xantrax Freedom 1800). I've planned the inverter into my system, but I see a potential problem.

    Lightning.

    I'll be able to isolate the inverter when the boat is out on the water, so with any luck, if I'm struck I won't lose the inverter. The boat will spend a lot of time at the dock though. Since it will be connected to shore power I see the potential for voltage spikes and I'd hate to lose my inverter that way. I don't see any marine specific A/C surge supressors.

    Has anyone dealt with this issue. I suppose I could just go to Best Buy, pick something up there and configure it between the A/C main breaker and the inverter.

    I'm just fishin' for ideas on this issue.

    Thanks in Advance and Regards,

    MIA
     
  2. CDK
    Joined: Aug 2007
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    CDK retired engineer

    If lightning strikes, you'll loose the inverter, no matter what you buy or construct to protect your equipment.

    Against lightning nearby and spikes in general you can use protection circuits based on Metal-oxide-varistors, like GMOV from General Electric. They are wired across the AC input lead directly after fuses. In case of severe over-voltage they start to conduct, creating a short circuit to immediately blow the fuses. For a 115 volts grid, types are used which start conducting around 150 volts but you can also use lower values like 125 volts. In the latter case the fuses will blow more often, like for example when someone switches a large motor on or off or a welding transformer.
     
  3. jdarling
    Joined: Jun 2009
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    jdarling Junior Member

    Well, its not quite as simple as saying you will loose the inverter. A TVSS (transient voltage surge suppressor) of proper size will protect you from most strikes. Though, the price tag on the thing will make you wish you had never even heard of the thing.

    As CDK stated, an expensive (comparatively) solution would be MOV's, but will offer less protection in high load locations.

    Of course, considering you are on water (I'm going to guess salt) you might be able to get away with an indirect water ground. Since I don't know much about protection and water itself (outside what my code books tell me) I don't know if it would really work. But, in theory, running a copper plate down the hull across the water and tying it indirectly to your neutral should protect against far strikes (nothing direct or fairly close).

    If your feeling really lucky (or have a large boat that ISN'T METAL) you could run a strip of copper for the neutral and a strip of nickel for the hot line on opposing sides of the boat. Contrary to popular belief, most, water will not conduct electricity. In the case of a high voltage strike, the water would become conductive (due to ionization) and would surround the boat in a charged shield (don't touch the glowing boat kids).

    Then again, as I said, its only if you really REALLY feel lucky.

    Personally, don't worry about it much, get a small surge protection system and if you get a direct hit replace the inverter.

    - Jeremy
     
  4. missinginaction
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    missinginaction Senior Member

    Thanks for the replys. I had a feeling that a small surge protector was the best I'd do in this situation, but thought I'd put this one out there to see if anyone else had an idea.

    MIA
     
  5. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Having suffered a direct lightning strike on a 54' cruising boat the only thing I could imagine protecting the boat would be not owning it. The through hull fittings were blown out of the boat, parts of the hull had boiled, glass was crystalized, and our entire electrical system was shot. In short, the boat was totaled and had it not been for the quick action of the marina it would have sank where it was. Heck the lead plates in the batteries melted.

    For a nearby strike a high quality surge protector is probably your best bet, and carry a little more insurance.
     
  6. Frosty

    Frosty Previous Member

    There is strikes and there is spikes.

    You can not protect from a strike (lightening) thats boating.

    A spike ( surges) will usually be handled by a good charger.

    I would have thought you had a good suply in New york.

    Personally I would spllt the 2 and reduce the risk of blowing the whole thing. Chargers are easy to repair, inverters hardly ever repair.
     
  7. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Good point, I have had plenty a charger fried at a dock, Also had inverter/charger fried. Next time, I wont combine both units.

    I believe that power at many marinas is not up to Home quality.
     
  8. CDK
    Joined: Aug 2007
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    CDK retired engineer

    That's what I meant in the 1th line of post #2.
     
  9. missinginaction
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    missinginaction Senior Member

    Thanks to everyone for the input. I will give serious thought to splitting the functions (separate inverter and charger). This seems like the most reasonable approach.

    Best regards,

    MIA
     
  10. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Missing,
    After a very quick peek at pricing it looks like a seperate charger and inverter will also save you a lot of money. Though the instilation might be a bit more time consuming.
     

  11. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    MOV's

    MOV's are indeed good solutions. One just have to be carefull in selecting the correct tolerance and Voltage level. A MOV is made up of many little grains. If a large surge takes place, some grains may get shortcircuit. Not a problem. But if your AC is 110 Volt i.e. x 1,414 peak = 155 Volt and the tolerance of the MOV is -20% / + 20% , you could lend up with some headaches if you buy a 150 Volt Varistor. If you are lucky and the tolerance is plus 18%, then it is fine, but if you are unlucky and you have one with minus 15% you will destroy your MOV and fuse. The clipping of the tip of the AC will heat your MOV up and either a small fire will start (we had 3 insurance claims in my carrier) or the fuse blows. Moral of the story, look for MOV's with -10%/+10% and use at least a 175 Volt type one, preferable a 200 Volt one. The manufacturer normally specify 1 mA leakage at indicated Voltage rating of the MOV.
    BertKu
     
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