Gasoline vs LP Fueled Generators

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #32
    Re: Gasoline vs LP Fueled Generators

    One thing to be aware of---Buried LP Tanks and fuel lines may not collect heat as well as in air (ignoring the issue of ~-40C temperatures).

    Even buried electrical power lines dissipate much less heat vs lines strung in air.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Mangas
    Mangas Solar Expert Posts: 547 ✭✭✭✭
    #33
    Re: Gasoline vs LP Fueled Generators

    Our ranch has a 500 gal LPG underground tank supplying the house and genset.

    We're about to add another one.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #34
    Re: Gasoline vs LP Fueled Generators
    ChrisOlson wrote: »
    ... That card has the information on it that tells the blending equipment what to blend in their load of fuel. ...

    ... The owner of the one gas station three blocks up has a pair of binoculars laying right on the counter and he looks down the street and sees Kwik Trip went up a few cents - so he rushes right outside with his long pole and changes his prices to match. ....

    Interesting info on the card. Must be used at the more modern depots. Still the only difference will be a few gallons of additive, the other 99.9% is the same base gasoline. Whatever the current mandated blend is for that season for that state.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #35
    Re: Gasoline vs LP Fueled Generators
    techntrek wrote: »
    Interesting info on the card. Must be used at the more modern depots. Still the only difference will be a few gallons of additive, the other 99.9% is the same base gasoline. Whatever the current mandated blend is for that season for that state.
    Same thing here in Nova Scotia. One refinery supplied all the brands in the area.
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #36
    Re: Gasoline vs LP Fueled Generators

    I think I'm going to make one final enhancement to my new generator installation - an automatic auto-throttle controller. When the generator starts it needs to come up to rated speed right away so the inverters can sync with it, and it has proper freq and voltage. But for load start it is typically running at full rated load, the load drops off so the inverter is done with it, and it just disconnects it and runs it for 2 minutes for cool-down, then shuts it off.

    I would like the engine to idle at 2,200 rpm for the two minute cool down so it doesn't flood the cylinder when the spark is suddenly shut off running at rated speed.

    I think I came up with a way - I installed a volt meter by the gen controller so I can monitor the voltage of the starting battery for the generator. I notice when it starts that the voltage is initially below 13.0 volts. But after it runs for 5 minutes or so the voltage gets up to 13.8 volts. The auto-throttle switch is just a simple SPST on/off. It is open for auto-throttle off and closed for auto-throttle on. A little ice cube relay can handle that part. I found an old Coleman air dump load controller board in a box of junk I had. I am going to set that up to monitor the genset battery voltage, and when it gets to 13.2 volts activate the "dump", which will engage the little ice cube relay and enable the auto-throttle.

    Just another use for some old stuff I had laying around ;)
    --
    Chris
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #37
    Re: Gasoline vs LP Fueled Generators

    I love shutting off the fuel and letting the engine run dry... Butt a couple people here worry about running lean during shutdown.

    Perhaps have load off and or at slow rpm would help.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #38
    Re: Gasoline vs LP Fueled Generators

    The inverter disconnects load and lets it run free for 2 minutes before it shuts it off. But that loads up the engine when it's running at 3600 rpm. If the auto-throttle is engaged, then it idles down when the inverter disconnects load. It also cools down better before it shuts off, and doesn't load up the cylinder.

    If a generator is to be stored for any length of time I think shutting off the fuel and letting the carb run dry is probably a good idea. Our generator is getting into the time of year when it will run every day for at least an hour at various times, so running the carb dry doesn't really pay.
    --
    Chris
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #39
    Re: Gasoline vs LP Fueled Generators

    I installed this new gizmo late this afternoon and it works!
    http://youtu.be/IzFUPKeNsiQ
    --
    Chris
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #40
    Re: Gasoline vs LP Fueled Generators

    Honda EM4000sx is rated at 0.61 gallons of gasoline at 3600 watt rated load. That is 69,500 btu's /hr. for 3.6 kWH's which is 17.7% efficiency.

    Running on propane it will consume more gallons per hour or about 0.8 gallons per hour at 3.6 kW rated load.

    Even a large generator will barely approach 25% efficiency. For a 4-5 kW generator, about 17% is typical for full rated load. It will average about 12% efficiency at mid-range loading. Propane is clean, good long term storage, and the most expensive fuel for a generator.
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #41
    Re: Gasoline vs LP Fueled Generators
    RCinFLA wrote: »
    Honda EM4000sx is rated at 0.61 gallons of gasoline at 3600 watt rated load.

    Where does this "rating" come from? I never seen no BSFC tests done on one before. Is this more "data" based on Honda's advertised run time vs fuel tank capacity off their website?

    Yesterday we had a bad day so I ran the generator for 2.5 hours to bulk the bank towards evening and did another measured fuel consumption test on it. It developed 7.6 kWh on my meter in 2.5 hours, which is an average output of 3.04 kVA for the run time. It's fuel consumption was 141 ounces on that run. That figures out to 20.6% efficiency on a real world battery charging job.

    After it gets a few hours on it I'm going to do another measured fuel consumption test using 10% ethanol blend to see if there's any difference.
    --
    Chris
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #42
    Re: Gasoline vs LP Fueled Generators

    You will not likely fine BSFC tests for a generator.

    Two sources.

    http://www.honda-engines-eu.com/en/images/111071.pdf on page 4 list 2.4 liters per hour at rated output which translates to about 0.63 gallons per hour.

    http://powerequipment.honda.com/pdf/Brochures/generator_brochure.pdf page 21 list 10.1 hours run time on 6.2 gallon tank at rated output translates to about 0.61 gallons per hour.

    Manufacturers usually stack the deck to optimize on their fuel consumption claims, starting with sea level base and optimum environmental temp for best fuel vaporization.
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #43
    Re: Gasoline vs LP Fueled Generators

    Well, something is a little wrong with their data that tells me it's not actual test data on the EM4000SX. The engine develops 6.8 hp @ 3,600 rpm @ sea level. The engine never reaches full rated output on the EM4000SX generator unless it goes into "iAVR mode" where the generator produces 5.0 kVA for 10 seconds. Rated continuous generator output only operates the engine at 70% of its peak rated power output.

    Therefore I'm sticking with my test numbers, because I have real world numbers from a real world installation.
    --
    Chris
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #44
    Re: Gasoline vs LP Fueled Generators

    I like Chris' measurements.

    I think generator companies look footer plausible deniability.

    I remember the old Honda eu2000i 1/4 power specification of 15 hours on 1.1 gallons of gasoline. Now it is 9.x hours per tankful.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #45
    Re: Gasoline vs LP Fueled Generators

    What Honda supplies for run time per tankful is a general guideline. It's not actual test numbers. The only real way to know what to expect from your generator is to test it on your own system. And no two systems are alike - some folks might like to limit their charging amps in the inverter menu so the generator runs at less load than it could. When I hooked up the new generator I run it until it got good and hot, then increase the max input amps until it popped the breaker on the generator. Then back it off two amps and that's what I use for max input. I set the charger amps to same as max input amps and let the inverter sort it out, depending on load.

    Turns out the breaker on the generator will handle more than what it says on it for quite awhile before it trips.

    This generally works the generator right to its raw limits and gets better efficiency from it. Other folks who don't like to work their generator as hard might not get the same efficiency.
    --
    Chris
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #46
    Re: Gasoline vs LP Fueled Generators

    It's always good to have real world test results. However, it's hard to understand why Honda would so massively underestimate the efficiency. :confused:

    Makes me tempted to test my EU2000s to see what their real world efficiency is when battery charging.
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  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    #47
    Re: Gasoline vs LP Fueled Generators
    mtdoc wrote: »
    It's always good to have real world test results. However, it's hard to understand why Honda would so massively underestimate the efficiency. :confused:

    It's called "CYA advertising". If it outperforms the claims, everybody is happy. If it under-performs people start complaining and asking questions.
    --
    Chris
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