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Buying a used generator

akjim | Posted in Tools for Home Building on July 5, 2009 04:34am

In the market for a used generator – approx. 5KW.  Will see light to medium use.

What is the best method to “test” a used generator?

 

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Replies

  1. junkhound | Jul 05, 2009 05:43pm | #1

    1. Does it start? Was it cols or already warm when you tested it?

    2. Take along a couple of 1.5 kW elec heaters, a 4 HP compressor, and a meter.  Meter that read frequency in addition to voltage the best - running no-load, turn on the heaters an check for how long the voltage droops.  Same thing with the compressor.

    Voltage and frequency should recover to 120 V, 58-60 Hz within  3-4 seconds.

    3. Leaks?

  2. frenchy | Jul 05, 2009 06:54pm | #2

    You are buying a pig in a poke..  Another words you really never will know what you're buying..

      Some of my contractors would clean everything up, change the oil for the first time in 3 years, and still get a really decent price for theirs..

     These were gen sets that had worked up to 12 hours a day for years.

     Do not buy any generator that does not have a Honda engine..   Manufacturers who used Brigss or other engines were really looking to cut costs by pennies simply to sell a price product..

     While they work OK for a while they are a price first product and thus not going to be as reliable as one with the Honda engine..

      The Honda engine starts well, runs relieably, vibrates less, and is quiete.r

     

    1. akjim | Jul 05, 2009 07:18pm | #3

      To check output, I understand using frequency to gauge condition of the generator.Probably makes the most sense to check frequency/change in frequency at 0 load, 50% load, and say 90% full load. Recovery to 60 hz the standard.Makes sense. Am I on the right track?Obviously leaks, how well it starts and runs/sounds, overall condition, etc. are big factors.What I am really trying to understand is judging a used generator's electrical output/quality.Jim

      1. brownbagg | Jul 05, 2009 07:38pm | #4

        problem with generators
        1) group sit in the garage for years with gas in the tank and then they run wide open, so oil gas problem.2) construction generator get beat and abuse in back of truck out in weather and rain, pulled off tailgate, used as saw house3) stolenbe safe go buy a brand new honda , baby it, keep it for years trouble free.

    2. VAVince | Jul 05, 2009 10:29pm | #5

      How many 5000 watt gensets have you sold??

      1. frenchy | Jul 06, 2009 01:03am | #9

        I helped several thousand contractors shut down as the housing market collasped  so I know what's going on..  I was one of the few vendors willing and able to work with contractors as they fell further and further behind in their payments.. The handful who remain in business worked closly with me to save their credit rating and retain value in their company..

      2. catfish | Jul 06, 2009 02:04am | #10

        As many as he could get.

  3. renosteinke | Jul 05, 2009 11:15pm | #6

    Alas, there's not really any good way to tell a 'good' genny from a 'bad' one, save price.

    That is .... not without an oscilliscope and load bank. I suppose another 'generator primer' is in order.

    The first rule is: don't buy more than you need, no matter the cheap price. Why westle a 125# beast off the tailgate, when you can easily hand-carry a lunch-box sized Panasonic to meet your needs?

    The second rule is: define your needs. If you're only using the genny to power motors and lights, you can tolerate a cheap genny with it's POS voltage regulator and crappy waveform. If you're putting anything electronic on that power, though - computer, TV set, even battery chargers - that crappy waveform and dancing voltage will kill you. The cheap genny will be the most expensive saving you ever made.

    Third is to fairly consider the ancillary issues: portability, how much space it takes in the truck, how much fuel it gobbles, how noisy is it, whether you can get parts.

    You want 'cheap at any price?' Go to the auto parts store and get their $200 roaring dragon. You want a proper genny for maybe one light and one tool? Look at the tiny $900 Panasonics and Hondas.

    Used generators are really one of those situations where you're buying someone else's problems.

    1. brownbagg | Jul 05, 2009 11:21pm | #7

      our company been buyinhg those lunchbox hondas, those puppies are great. not cheap but great. I bought a geeny , new before 2k, its been inthe garage since, dont know if they gas in it or not, dont even know if it runs.for hurricane everybody been getting those natural gas pernmant units that set outside on a slab. but they can burn $200 a week in fuel.

    2. junkhound | Jul 06, 2009 04:12am | #11

      auto parts store and get their $200 roaring dragon

      I got mine on sale for $99 at Schucks (after rebate), could not pass it up just to see how good or bad it was. Surprised me on the good side.

      Now, I've worked on everything from 6000HP/4MW  CAT/AVK 11kV gen sets on board ships down to chain drive homebuilt 12 kW driven by old Datsun engine and the 'roaring dragon', so was really interested in what $100 retail would get you.

      Surprisingly, the little 2 cycle (40:1 oil) is surprisingly quiet.  Drives enough to run a 12A sidewinder if you dont try to rip 4X material fast.  Easy one hand carry.

      However, it would not start my 1 HP/ 120V compressor even at no pressure. 

      Once you master the finicky choke, starts right off.

      Ran battery charger, TV and VCR at cabin last week with it, quieter than my old 1800W Techumsah gen set.  

      That little thing is so handy, have actually come to like it.  Gets used more already than the trailer mounted Wisconsin engine 20 kW setup.

      1. JulianTracy | Jul 06, 2009 05:34am | #12

        One gem of a genny to look at is the Honda EB3000c. It is a 300watt model, it'll run a small air compressor... but best of all, it weighs only 68lbs!Most of the 2900-3000 watt units weigh close to 115lbs empty.I had a Tursumi 2900 watt - their big selling point was crazy run time, but it wouldn't handle the air compressor startup. This little Honda will.Also - pretty huge feature is the clean power it generates. They're fuzzy on details, but the cyclocovertor technology seems similar to the EU series in that the power fluctuation is very low.Most other genny's fluctuate between 105-130volts or so, this unit stays consistent at 118-122 in my experience.But the weight is huge to me. 115lbs is ridiculous for loading in the truck, 68lbs is doable.Also - if you want a bit of flexibility and cross-usage, you can buy (2) 2000watt EU Hondas and run them in parallel as one 4000watt unit.I've had a Honda EX650 for 5 years now and my Grandfather had it since brand new, maybe 10 years before I got it. Still runs like a champ and starts up like a pro.Spend the money, buy a Honda, but I wouldn't be afraid of buying used, you got to trust your gut about the folks selling it...JT

        1. Scott | Jul 06, 2009 10:56am | #13

          I think the OP said he wanted something in the 5KW range.

          1. ANDYSZ2 | Jul 06, 2009 03:02pm | #14

            I think one of your best options is going to the big box stores in a storm struck area and looking for a reconditioned model.

            People bring back the generators they just bought .It is gone over by the repair shop returned, to the store and sold at least 25% off .

            I looked at a nice suburu motor 6500 watt for 650$ just yesterday.

            ANDYSZ2WHY DO I HAVE TO EXPLAIN TO FRIENDS AND FAMILY THAT BEING A SOLE PROPRIETOR IS A REAL JOB?

            REMODELER/PUNCHOUT SPECIALIST

             

          2. User avater
            IMERC | Jul 06, 2009 07:28pm | #15

            yeah but is that 5W nominal or surges to.... 

            Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

            WOW!!! What a Ride!

            Forget the primal scream, just ROAR!!!

             

            "Some days it's just not worth chewing through the restraints"

          3. Scott | Jul 06, 2009 08:25pm | #16

            >>>yeah but is that 5W nominal or surges to....Nominal; it says surges to 6250W, but I take that with a huge grain of salt. It has a hard time running our 3/4hp 240V well pump.Scott.

          4. User avater
            IMERC | Jul 06, 2009 08:34pm | #17

            yur 5kw has a hard time running yur well...

            is there other stuff on the generator too??? 

            Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

            WOW!!! What a Ride!

            Forget the primal scream, just ROAR!!!

             

            "Some days it's just not worth chewing through the restraints"

          5. Scott | Jul 07, 2009 06:13am | #19

            >>>is there other stuff on the generator too???No, I've got a transfer panel which lets me isolate loads.When the power goes out, I start by running lights and fridges. When the water runs out (the pressure tanks can't push any more) then I cut off the lights and fridges, and run the well pump to fill up the pressure tanks again. As the tanks near their capacity, the motor load grows and I can hear the generator struggling. The sound of the pump motor (225 ft. down) also changes, and sounds unhealthy. At that point I hit the pressure switch to kill the pump. I don't want to hurt that motor because I dread the day I have to pull it up.It only happens once or twice a year.Scott.

          6. User avater
            IMERC | Jul 07, 2009 06:20am | #20

            something's not right...

            1 hp is something like 750 watts and you have a 5,000 watt generator...

            yur well wants 560/565 watts or there abouts....

            240V or 120??? 

            Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

            WOW!!! What a Ride!

            Forget the primal scream, just ROAR!!!

             

            "Some days it's just not worth chewing through the restraints"

          7. Scott | Jul 07, 2009 07:07am | #21

            240VAnd it's 225 feet down the hole, so there's bound to be some line loss, in spite of (IIRC) #10 conductors.Scott.

          8. User avater
            IMERC | Jul 07, 2009 07:18am | #22

            not that much...

            best start loking at yur generator... 

            Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

            WOW!!! What a Ride!

            Forget the primal scream, just ROAR!!!

             

            "Some days it's just not worth chewing through the restraints"

  4. Scott | Jul 06, 2009 12:10am | #8

    The Honda's may be good, but you'll pay for it. FWIW, I've got a Coleman/Briggs unit that has been a great machine, but I take good care of it. I change the oil regularly and always drain the gas when not in use. If you can find one like this, you'll be fine with "light to medium use".

    I like Junkhound's suggestion about taking some loads along. And ask the guy some basic questions about how he maintained it. Check the air filter... that often gets forgotten, and can give you a sense of how careful the guy was.

    Scott.

  5. gb93433 | Jul 06, 2009 11:14pm | #18

    Check the play in the throttle shaft of the carburetor. That is a good indicator of its running time.

    Check the compression.

    Check to see if the valves leak by pulling the rope slowly and listen for noise of air going by the valves.

    When it is running put a full load on it to see how the machine responds.

  6. Roger6 | Jul 07, 2009 09:06pm | #23

    I just happen to have an Onan 6.3KW propane powered generator for sale. Unit is 10 years old with 25 hours on a total engine-generator rebuild. The unit was originally installed as a backup for a photo electric system. I sold the unit new and then bought it back when the original owner finally put in utility power (He got married and had two kids)   I have it mounted on dolly. Contact me directly if interested,  Asking $1500.00 with manuals and remote start kit. Owning and maintaining a stand by generator takes a little planning. The advatage of a propane powered unit is that you don't have to deal with fuel that goes bad sitting around. I periodically start this unit using a 20lb LP tank and external regulator. I usually plug in a couple of 1.5KW electric heaters and run my 2HP air compressor the powers my nail gun. Roger

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