Know enough about generators to answer this one?

This is a discussion on Know enough about generators to answer this one? within the Off Topic & Humor Discussion forums, part of the The Back Porch category; New generator just got here from generatorsales.com. Looks good, no shipping damage. Got to looking at it and I seem to have a problem. Well, ...

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Thread: Know enough about generators to answer this one?

  1. #1
    Senior Member Array madmike's Avatar
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    Know enough about generators to answer this one?

    New generator just got here from generatorsales.com. Looks good, no shipping damage.

    Got to looking at it and I seem to have a problem. Well, maybe I do, maybe I don't. You tell me.

    The website says it is rated a max output of 56.25 amps @ 240v and 33.3 amps @ 240v. But the thing has a 30 amp breaker in the 240v output.

    So, if my demand tries to pull a surge-load of more than 30 amps, won't that breaker trip?

    I might be missing something, but I don't see how it can supply the stated surge load with that breaker in there.

    It also has a pair of duplex 120v outlets, each duplex has a 20 breaker. I see the same problem with it supplying the stated surge load for it's 110v outlet, 112 amps, much less its continuous 110v output of 66.7 amps.

    I was thinking I could supply my existing electric service box, through a power transfer switch, 240v from the generator, just like the electric company does, and not have to use those 110 outlets on the generator.

    Anyone able to shed some light on this? Am I going to have to separate my 240v and 120v circuits?

    I have emailed the people I bought the generator from with my concerns, but I do have doubts they'll be much help. The electrical install will be done by an electrician, but I don't know if he really knows the "ins and outs" of generators, but he does know the local codes.

    mm
    Political Correctness has now "evolved" into Political Cowardice.

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  3. #2
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    Mike - if as it seems, it is rated 8K continuous then that is just above the breaker threshold but would probably get by.

    If the breaker is a surge compatible type then very possibly it will ''permit'' the peak surge load for a small time before tripping out - probably several msecs. I would suspect that is the case. As current exceeds the rated loading there is a temperature rise slow enough to buffer the surge before tripping.

    Once a start-up surge such as from a motor, compressor etc is satisfied then all being well draw will drop back to continuous running levels. If breakers were rated too high and actually permitted sustained excess loads over the gen'y limit - it would of course be self-defeating and the unit would probably burn out its windings!

    My new switching panel goes to outside where I would hook up the gen'y if needed - plug in emergency cable to gen'y 240v out- all I do then is disable the power Co main fuses to avoid any backfeed from the main distribution panel.
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  4. #3
    Senior Member Array madmike's Avatar
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    Perhaps no more dangerous words were ever spoken, second only to "Hey yall, watch this!" but I have to say, that make sense to me.

    I will continue to look into it, but I suspect you are right about how that works. At least, this is something I can try and risk only a tripped breaker.

    Thanks!

    Mike
    Political Correctness has now "evolved" into Political Cowardice.

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    VIP Member Array Bud White's Avatar
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    It will surge to that amps for a limited before it pops the breaker

  6. #5
    Senior Member Array madmike's Avatar
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    Thanks guys!

    This is making more sense to me now. It does give the continual run amperage as being 33.3, and the breaker in that circuit is a 30 amp.

    This is gonna' work, just fine.

    Interesting though, the guy that delivered it said that I should make certain I followed the instruction's advice and add the supplied oil before starting it up. He said is was "illegal" to ship engines by motor freight (boxed up and all) with oil in them.

    Nice of him.

    So, I checked the oil level, it was full! The two bottles of oil were still in the box, unopened. I also took a look in the gas can and found about a half-gallon in there!

    So much for shipping regulations.

    Anywho, I read the book and fired it up, the thing runs smooth and quiet. The only load I put on it to make sure it worked was an electric drill and then a 2hp electric air compressor. Both worked and the generator didn't seem to notice.

    I'll get with my electric guy, then contact the propane people so they can install the 250 gallon system.

    Looking GOOD!

    mm
    Political Correctness has now "evolved" into Political Cowardice.

  7. #6
    VIP Member Array Bud White's Avatar
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    the guy is right it is illegal to ship them full of oil

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    VIP Member Array Sheldon J's Avatar
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    The website says it is rated a max output of 56.25 amps @ 240v and 33.3 amps @ 240v. But the thing has a 30 amp breaker in the 240v output.
    Typo? Do you mean 56.25 amps at 110 which is the combined total output current of both legs which is about 6 KW or only about 28 amps per leg well under the 30 max load.
    It also has a pair of duplex 120v outlets, each duplex has a 20 breaker. I see the same problem with it supplying the stated surge load for it's 110v outlet, 112 amps, much less its continuous 110v output of 66.7 amps.
    We need to do a little more math here, the 30 amp's is per leg you have a 6.2KW generator with a 7.9KW surge propably called it a 6 KW with a 8 KW surge, short druation burst such as when a motor is starting will not normally kick out a braker it'll run the fridge and TV with no problem.
    "The sword dose not cause the murder, and the maker of the sword dose not bear sin" Rabbi Solomon ben Isaac 11th century

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    your average breaker will tolerate a slight overload for about 5 seconds. this is for motor starting. a/c, pump, refridge, etc.


    if you're using the 240 output, you can still use the 120 outlets, but you run the risk of overloading the unit.

    all the 240 is, is both 120 outputs combined.

    calculate your total expected loads and make sure it doesn't exceed 80% of the continuous output.

    going over 80% except for motor starting and short times beats the gennie to death. they will burn out without tripping a breaker if run to close to max output all the time.

  10. #9
    Senior Member Array madmike's Avatar
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    Thanks for the input More is better!

    Not a typo, I'm just quoting the numbers given on the web site.

    They sell this one as an 8kW model, with a 13.5kW surge capacity. To see exactly what I'm talking about, go to www.generatorsales.com and use the "lookup model" feature in the upper left corner of the page. The model # is 04364.

    I don't plan on running things thru extension cords, that would really complicate things, such as figuring a way to hook my well pump up to the 240v outlet and then run several other extension cords for the 120v. I know that can be done, but I'd not like to do it that way, since a hurricane power outage can go several weeks.

    I'll be using a power transfer switch to put the 240 into the existing electric service box. Once I've mapped-out all the switches, I'll then turn off all but the essential breakers.

    mm
    Political Correctness has now "evolved" into Political Cowardice.

  11. #10
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    using your existing box is the way to go. that way you only need a big 240 volt cord.

    if your well pump is running through your existing box, running a separate cord for it is not neccessary.

    i had to use romex for what i needed after andrew because most of my conduit was full of water.

    if you have to use your gennie after a storm, make sure your wiring/conduit (if used) is dry and tight, otherwise you'll be calling the f.d. or ambulance service.

    also, start the biggest loads first, then apply the smaller ones.

    it wouldn't hurt to run it for a few hours with a light load to break it in. after running about 5 to 10 hours, change the oil and filter.

    as for most of the surge ratings i've seen, they're a little optomistic. it takes approx. 2 hp. to generate 1000 watts.

  12. #11
    Senior Member Array madmike's Avatar
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    The only reason I thought I might have to run the well on its own separate circuit was because I wasn't certain that I would be able to get the full power available from the genny thru that single 240 outlet.

    Now, I'm pretty sure I can, so I will feed it thru the exiting service box, and of course, using a power transfer switch.

    That "big 240v" cord will be a nice, short one, as I'll be putting the genny right next to the power meter, outside the house.

    First, I don't trust the labels on the breaker switches, since there's been changes made over the years. So I will be going thru the house and mapping every outlet to each individual breaker.

    The ones I want to keep "hot," will be clearly marked in red. When I need the genny, I'll first turn off ALL the breakers, throw the transfer switch to "emergency power," and start the genny. After a few minutes of running without any load, I'll turn the power switch on the generator itself ON. (Until then, the genny motor is running, but it it's power outlet panel is not hot.)

    At that point, I can start turning on the "essential circuits." The well would come on last, and I will probably restrict water use and only turn the well on, when actually needed.

    As far as working with voltage and amps, I've done that for a living in the past. I do have a healthy respect for electricity and am very familiar with what it can do to you, as well as for you. But I do appreciate the cautions offered! That sort of thing you cannot hear enough.

    I'm of the opinion that it isn't "pride" so much that "goeth before a fall," its actually "complacency."

    mm
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    that's a good idea. i got all my breakers marked. before i bail to my shelter i turn off everyone but the fridge. turn off the gas and water too.

    the 240 outlet gives you all the output of the gennie, so no problems there.

    you might want to start the well first. those things pull some amps starting depending on size. then you can turn it off and on and juggle loads as needed. pain in the butt, but better than no juice.

    be sure to ground the gennie. they have ground lugs on them. i use a piece of wire attached to a metal rod and drive the rod 2 feet in the ground.

    on tri fuel gennies, most rate their output on gasoline.
    deduct 10% for lp, and 20% for n.g.

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    Senior Member Array madmike's Avatar
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    Good idea on the ground, probably won't do to just tie it in to the house ground. And I'm sure there's some "code" involved as well.

    I'll probably pick up a ground rod, around here, you really have to sink them quite a ways to be effective due to the rather dry, sandy soil. Whatever the code is, I'll do that, maybe more.

    mm
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    VIP Member Array Sheldon J's Avatar
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    What fuel are you going to use, tri fuel is a good idea however you need to know that you loose a certain % of capacity for fuel other than gasoline, and I believe it is around 15% for natural gas and 20% for propane.

    I'm running a 10kw cont with a 13 kW surge gasoline and have no issues on a mostly electric house. I looked at a very similar model prior to buying mine, but with an electric hot water heater I needed the capacity.

    If you go to the printable page you will see that they have a typo on the main page it is 66.7 @ 112.5 also they are being a bit deceptive here the model 7500 represents the actual rating of the unit.

    Their figures of a 13.5kw surge for a 7.5 kW continuous seems a bit out of spec for what it should be rated at.

    Someone said you can use the 110 while using the 240, they said it was a bad idea, well it is a real bad idea, two words unbalanced load. Wiring a feed into your house, as long as you have a method to isolate from the local power grid is the way to go. You do not want to back feed the mains, it could kill someone.

    They are using a 30A twist loc recpt. Like the breaker it too can handle short burst above rated. If you are not experienced at this I would recommend you hire an electrician to complete the hook up.
    "The sword dose not cause the murder, and the maker of the sword dose not bear sin" Rabbi Solomon ben Isaac 11th century

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    Senior Member Array madmike's Avatar
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    I am having a licensed electrician do the hook up, but again, thanks for the caution.

    I will be using the 240 outlet from the genny, to supply power to the service box, in conjunction with a power transfer switch.

    I understand how back-feeding the grid could well be dangerous, but more than likely, it would simply trip the breaker in the generator, long before anyone is out working on any thing. After all, this one will not run my house completely, let alone the neighbor's on the grid.

    The reason I'm going with propane is that I already have it for my stove and oven, hot water heater, and clothes dryer. Now, to my way of thinking, the last two of those three are hardly what I'd call "necessities." More like "nice-ities." Have to say though, a shower with water straight of that well can be pretty invigorating, if not actually heart-stopping.

    I want to be able to keep things going for more than just a day or so. Keeping enough gasoline on hand to do that is problematical. I'm not real sure just what obstacles the local codes might throw up. Keeping a large supply of gasoline when I normally wouldn't have much of a need for it means stockpiling and stabilizing, maybe trying to use it in the "off season" and rebuild the supply when the time comes. Besides, all that transferring gas around sounds like a pain in the backside.

    Propane, for me anyway, solves a lot of that. It does not need to be "stabilized," and I already know the local codes and they are no problem.

    The cost involved are minimal, just trade in my current 125 gal. tank, for a 250 gal. Pay the difference for the complete fill, then the gas company will keep it topped off, as they do now.

    As it is, the tank gets a top-off that only involves 40 gallons on the average. My use will not see much of an increase, except that which I'll burn off running the genny once a week to keep it ready.

    If I get nervous about it, the local code will allow me to add additional 125 gallon tanks, without moving them further from the house.

    I'll be getting back with the gas guys as soon as my work schedule permits.

    mm
    Political Correctness has now "evolved" into Political Cowardice.

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