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  1. #1
    Join Date
    Aug 2007
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    720

    Default Generator Question

    I have a Coleman 5000 watt generator that I use occasionally. The salesman at a local lawn and garden equipment sales store told me that my generator will only put out 1/2 of it's claimed output after running for thirty minutes. Is this true or is he just trying to sell me a new generator?
    Thanks,
    Nick

  2. #2
    Join Date
    May 2007
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    224

    Default

    Did he load test it, to come up with that conclusion? Sounds like he's working on commission, and needs sales.
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  3. #3
    Join Date
    Dec 2007
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    Los Angeles
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    Default

    Never heard of that before- maybe he misread the specs about fuel consumption

    "Runs up to 11 hours @ 50% load"

  4. #4
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    Aug 2006
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    Default

    I've heard of this before, it's called crapola.......something to do with science
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  5. #5
    Join Date
    Aug 2006
    Location
    Plainview, TX
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    334

    Default

    Most generators such as the Coleman Powermate that you have, have a Max Load and Continuous Load. Also, if you are wanting to get the most Fuel Efficient and longest run time, there is another load, generally around 50% of Rated Continuous Load.

    The Max Load, generally related to Inrush Current and Max Amp Draw of the load being run, is listed for a short time interval, such as the 30 Minutes mentioned by the lawn equipment guy. The Continuous Load is generally the load that can be sustained for an extended period of time. However, for MAX RUN TIME, it is generally recommended to only run at 50% of Rated Continuous Load.

    An Example I have seen, 5000 Watt Generator. Max (Peak) Load (30 Minutes) 5500 to 6250 Watts, depending on the power windings. Max Continuous Load, 4000 to 5000 Watts, depending on windings. Max Run Time Load, 2000 to 2500 Watts, also depending on winding.

    For what your generator is actually rated at, consult the Owners Manual or the Manufacturers Website for your particular model. But it also sounds like the sales guy, doesn't know what he is talking about.

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  6. #6
    Join Date
    Aug 2007
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    720

    Default

    The saleman actually said that the Honda generators loose about 10% after thirty minutes and the Coleman looses 50% after thirty minutes. Without trying to sound biased, they are a Honda dealer.

  7. #7

    Default

    Tell him to show you proof. I have an old 4000 watt Coleman that I initially bought to hook to an old buzzbox to weld with. I can tell you that it ran near at or over rating for well over 30 minutes. Ask the guy why this is the case.

    Max Continuous rating is just what it say Max Continuous, it should run at those watts until it doesn't run any longer. Generators are just like any other mechanical thing, run them at redline and they won't last quite as long.

  8. #8
    Join Date
    Oct 2008
    Posts
    28

    Default

    We design and build larger generators. 20 - 150 kW models. The basic principles are the same though.

    You sales man is correct. I do not know the specs on the Coleman's engine, however ALL power units have two ratings. Continuous and Standby (intermittent). For various reasons that would take a book to explain, engines cannot run forever at a given horsepower. A Corvette may have "550 hp" but that is basically an intermitent load. If you were were to evaluate it on a "continous" basis it would be MUCH less. Perhaps 200 hp. Gasoline engines lose alot more horsepower between intermittent duty and continous duty compared to a diesel.

    Since your generator is engine driven, it has a subsequent Prime and Standby rating. Normally, prime is about 75%-85% of standby rating. This is basically the same reason welders have duty cycles. When Coleman and most other people advertise or rate their gensets, they almost always give you the higher kW rating (standby) because it sounds like you are getting more for your money.

    You also should consider what you will be running with the genset. If you will be running electric motors alot as opposed to lights, etc, I would recommend buying up to 50% more kW than you think you will need. Motors take more wattage than they are rated for during hte startup and if you dont have the wattage, you will burn up starter windings in the electric motors. Another thing is that ideally, you want to run your generator around 75% of capacity for longer life.

    I know this is an old thread but thought I would pipe in my 2 cents.
    Last edited by ChiliDog; 11-02-2008 at 10:39 AM.
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  9. #9
    Join Date
    Feb 2006
    Location
    Northern CA, Shasta CO.
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    144

    Default

    You sales man is correct. I do not know the specs on the Coleman's engine, however ALL power units have two ratings. Continuous and Standby (intermittent). For various reasons that would take a book to explain, engines cannot run forever at a given horsepower. A Corvette may have "550 hp" but that is basically an intermitent load. If you were were to evaluate it on a "continous" basis it would be MUCH less. Perhaps 200 hp. Gasoline engines lose alot more horsepower between intermittent duty and continous duty compared to a diesel.

    Since your generator is engine driven, it has a subsequent Prime and Standby rating. Normally, prime is about 75%-85% of standby rating. This is basically the same reason welders have duty cycles. When Coleman and most other people advertise or rate their gensets, they almost always give you the higher kW rating (standby) because it sounds like you are getting more for your money.
    Fill me in here tho. What you describe isn't so much of an 'ouput' issue as it is an 'engine life' issue. From what I'm getting here is that the engine isn't designed for extended full load duty, not that the genset will start putting out less, ie shortened life expectancy of the engine and not reduced output??

    I visualize full load for whatever length of time I choose to demand it until 1) the engine pukes whether that's three hours or three years, 2) some thermal device on the engine shuts it down, 3) some thermal device on the generator/alternator shuts things down. What I can't visualize is reduced output after thirty minutes.

    Sounds to me like either a misunderstanding on the salesmens part or, still, a marketing style play on words??

  10. #10
    Join Date
    Dec 2007
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    Los Angeles
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    Default

    It is poor wording by the sales dood.

    This from my Honda EU200i genset

    " Limit operation requiring maximum power to 30 minutes. Maximum power is 2,000va"

    " For continuous operation, do not exceed the rated power. Rated power is 1,600 va"
    Last edited by Broccoli1; 11-02-2008 at 01:24 PM.
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