Parallel generators

Discussion in 'Home Power and Microgeneration' started by Sudy Nim, Sep 1, 2007.

  1. Sudy Nim

    Sudy Nim Guest

    Is it possible to run two portable generators in parallel?
    Sudy Nim, Sep 1, 2007
    #1
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  2. In article
    <ypfCi.481194$>,
    "Sudy Nim" <> wrote:

    > Is it possible to run two portable generators in parallel?
    >
    >


    Yep, we do it ALL the time. All it takes is a BIG Pile of Money
    to modify the gensets with Electronic Governers, and install
    the REQUIRED SwitchGear, and your all set......

    or you could buy yourself a couple of Honda Inverter/Gensets
    and the Parallel Cable Kit and do it that way with those
    specific Gensets.....

    Bruce in alaska
    --
    add a <2> before @
    Bruce in Alaska, Sep 1, 2007
    #2
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  3. Sudy Nim

    Sudy Nim Guest

    <snip>

    Thanks Bruce in Alaska & Ulysses for your replies. I chased electrons in TVs
    and other stuff until I (forcedly) retired 15 years ago. House wiring I know
    that the white wire connects to white and black to black. In general I
    understand what you are saying but have no experience in it so I'm lost.
    Could you point me to someplace to get a little info? I realize that two
    generators need to be timed together and of equal output and balanced in
    some way. If it were too expensive or complicated I would just take a pass
    to something simpler.

    I live in a rural area (way) outside Chicago and have a private well for my
    water source. Being a stepchild to any town, I experience power outages
    randomly several times a year and purchased a Generac 4000exl, which serves
    all my needs except for air conditioning on occasional hot humid summer
    nights. So I'm pondering to either buy a larger generator, an additional one
    or live with what I got.
    Sudy Nim, Sep 1, 2007
    #3
  4. On Sat, 01 Sep 2007 21:45:56 GMT, Sudy Nim <> wrote:
    > Could you point me to someplace to get a little info? I realize that two
    > generators need to be timed together and of equal output and balanced in
    > some way. If it were too expensive or complicated I would just take a pass
    > to something simpler.


    It's not hugely complicated, but very easy to screw it up.

    First off, as someone else mentioned, you either need to buy the right
    generators (that are designed to be run in parallel) or strike out on
    your own.

    To do it manually, you need to be able to control the speed of at least
    one generator, preferably both. (I don't think you easily can with the
    4000exl.) Also, both generators need to have governors that will keep
    them at speed. Being able to maintain speed will help them properly
    share the load.

    If memory serves the following might be correct...

    a) Disconnect all loads from both generators.

    b) Connect ground and neutral between both.

    c) Call the two hots "high" and "low" on both generators. Make
    certain the polarity or phase is correct -- both high the same, both
    low the same.

    d) Wire double-pole switch (rated for full generator current) to
    simultaneously connect high to high and low to low.

    e) Connect light bulb between the two highs on the generator side of
    the switch.

    f) Make certain the switch is off (generators separate).

    g) Start both generators.

    h) With both at speed, adjust the speed so the light bulb stays dark.

    i) Close the switch (paralleling the generators).

    j) If it doesn't blow up one (or both) of them, you succeeded.

    k) Connect the loads.

    Shutdown is reverse:

    k) Disconnect the loads

    i) Open the switch

    g) Stop both generators

    (All that may be correct, but you are on your own!)

    > I live in a rural area (way) outside Chicago and have a private well for my
    > water source. Being a stepchild to any town, I experience power outages
    > randomly several times a year and purchased a Generac 4000exl, which serves
    > all my needs except for air conditioning on occasional hot humid summer
    > nights. So I'm pondering to either buy a larger generator, an additional one
    > or live with what I got.


    I have a 4000xl (from the pre-Briggs days). It's a nice unit. The only
    way I'd try to parallel it with another generator is if I was resigned
    to replacing the two generators anyway. I use it in parallel with a
    Trace (ne Xantrex) SW inverter to power larger loads. (See "generator
    assist.")

    sdb

    --
    What's seen on your screen? http://PcScreenWatch.com
    sdbuse1 on mailhost bigfoot.com
    sylvan butler, Sep 2, 2007
    #4
  5. Per Bruce in Alaska:
    >or you could buy yourself a couple of Honda Inverter/Gensets
    >and the Parallel Cable Kit and do it that way with those


    Tangential question: Can Honda inverter-based generators of
    different sizes be paralleled? e.g. Can an EU2000 be hooked up
    in parallel with an EU3000is?
    --
    PeteCresswell
    (PeteCresswell), Sep 2, 2007
    #5
  6. The message <>
    from Dale E <> contains these words:



    > sylvan butler wrote:


    > > On Sat, 01 Sep 2007 21:45:56 GMT, Sudy Nim <> wrote:
    > >
    > >>Could you point me to someplace to get a little info? I realize that two
    > >>generators need to be timed together and of equal output and balanced in
    > >>some way. If it were too expensive or complicated I would just take a pass
    > >>to something simpler.

    > >
    > >
    > > It's not hugely complicated, but very easy to screw it up.
    > >
    > > First off, as someone else mentioned, you either need to buy the right
    > > generators (that are designed to be run in parallel) or strike out on
    > > your own.
    > >
    > > To do it manually, you need to be able to control the speed of at least
    > > one generator, preferably both. (I don't think you easily can with the
    > > 4000exl.) Also, both generators need to have governors that will keep
    > > them at speed. Being able to maintain speed will help them properly
    > > share the load.
    > >
    > > If memory serves the following might be correct...
    > >
    > > a) Disconnect all loads from both generators.
    > >
    > > b) Connect ground and neutral between both.
    > >
    > > c) Call the two hots "high" and "low" on both generators. Make
    > > certain the polarity or phase is correct -- both high the same, both
    > > low the same.
    > >
    > > d) Wire double-pole switch (rated for full generator current) to
    > > simultaneously connect high to high and low to low.
    > >
    > > e) Connect light bulb between the two highs on the generator side of
    > > the switch.
    > >
    > > f) Make certain the switch is off (generators separate).
    > >
    > > g) Start both generators.
    > >
    > > h) With both at speed, adjust the speed so the light bulb stays dark.
    > >
    > > i) Close the switch (paralleling the generators).
    > >
    > > j) If it doesn't blow up one (or both) of them, you succeeded.
    > >
    > > k) Connect the loads.
    > >



    > How do the genny's maintain sync?


    In exactly the same way that the large PSU's generators (national grid
    connected power station generators) do.

    A synchronous AC motor is essentially the same as an AC generator
    (excepting the obvious starting/control gear differences). Once a
    generator set (steam or gas turbine powered) is up to speed and in phase
    with the grid, it can be connected to the power station's transformer
    bus. Thereafter, the more steam or throttle it is given the harder it
    will 'push' (production of amps into the load which boosts the grid
    supply - i.e. exporting electrical power).

    However, if the steam or fuel is throttled back, the generator will
    remain in sync by using power from the grid (it will then act as a
    synchronous motor). The effect will be to increase the load on the
    remaining generator sets connected to the grid which will cause them to
    slow down a little as well as cause the grid supply voltage to droop a
    little (which will reduce the amount of power taken by the load on the
    grid by a similar fraction - assuming the major load does not comprise
    wholly of SMPSU powered devices :).

    In a 'national grid' setup, there are various classes of power
    stations, amongst which will be main stations which will adjust their
    power delivery by increasing or decreasing their generator set speed
    from a a national time standard derived 50 or 60 Hz reference so as to
    average exactly a 50 or 60Hz frequency over each (and every) 24 hour
    period. The adjustments appear to be applied at about 4 per minute.

    The rest of the power generating plant connected to the grid will
    simply remain in sync following the changes of frequency being imposed
    by the main station(s).

    In any decent sized grid system, it's unlikely that the largest
    generator in a main power station will be called upon to provide more
    than 5% of the total load on the grid (more likely less than 1%) so the
    problem of dealing with the effect of an outage of prime motive power in
    a generator set on the rest of the grid (loss of steam delivery or blown
    turbine casing, or whatever) is much less than in the case of a two
    generator home power setup.

    Here (dual generator home power setup), each generator will probably
    only have a 60 or 70% capacity of the total load. An outage of one of
    the generators will almost certainly shutdown the other due to overload
    (unless the load just happens to already be within the capacity of the
    remaining generator). Essentially, a dual generator home power setup
    simply lacks the 'redundency' that's built into the national grid setup.

    If you're planning on a home power multi generator system, you need at
    least 3 generator sets to gain a reasonable benefit in terms of
    reliability of supply. In this case, ideally, each generator will be
    rated for one third of the absolute maximum load and have a short term
    (5 or 10 minutes?) overload capacity of 50% above their maximum
    continuous rating (as well as the obvious extra synchronising control
    gear to permit such combining onto a common supply busbar).

    As has already been pointed out, it's probably best to keep the two
    generator loads seperate rather than combine them. Here, you might
    seperate the loads into critical and optional loads with a swap over
    switch between the generators and their loads (perhaps using an
    automated relay operated swap over switch designed to give priority to
    the critical load so that it remains connected to a working generator
    regardless of whichever fails - or is shutdown).

    One major consideration with seperately loaded generators is the issue
    of safety. This arises whenever there is the possibility of the two hot
    phase voltages being present within arm's reach of each other.

    Since the generators are both free running and, for safety's sake, have
    a common 'neutral' and ground connection, the hot phase voltages will be
    going in and out of phase. This means, (in the extreme case of identical
    voltage magnitude) that the voltage difference between the two phases
    will vary from zero voltage to double the generator voltage at the
    difference frequency (maybe as low as half a Hertz or less) which makes
    the shock hazard even more lethal than in the single generator
    situation.

    Provided this potential hazard when running two generators into
    seperate loads is taken care of, this method offers a better solution to
    the combined into a single load method (unless you're prepared to invest
    in generator sets with at least a short term rating equal to the total
    maximum load - i.e. bigger, more expensive generators).

    HTH

    --
    Regards, John.

    Please remove the "ohggcyht" before replying.
    The address has been munged to reject Spam-bots.
    Johnny B Good, Sep 2, 2007
    #6
  7. Sudy Nim

    Ray King Guest

    The belt also absorbs vibration and damps any sympathetic
    > torsional resonance.
    >
    > Two heads on a suitably large engine is certainly viable.
    >
    > John
    > --
    > John De Armond
    > See my website for my current email address
    > http://www.neon-john.com
    > http://www.johndearmond.com <-- best little blog on the net!
    > Tellico Plains, Occupied TN
    > Nuke the Whales!
    >


    I agree a belt is better than welding but the generators will phase lock on
    their own. Because a motor is a generator and vice versa at least in this
    case. The paralleling has two issues. The phase syncing and voltage
    equalization. The gas/diesel engines will lag depending upon their load as a
    percentage of its rating not to exceed 100 %. If this starts to happen the
    generator will turn into a motor and there will be no load on the slower
    generator ( watch the first generator throttle position to make sure it
    never drops much below the other generator.one generator will try to become
    the master) The second problem of voltage equalization between two
    generators suggests both generators should be tested to have the same no
    load out put voltage. The safe proceedure is to add field control to match
    the output voltages.
    Ray
    Ray King, Sep 2, 2007
    #7
  8. Sudy Nim

    Sudy Nim Guest

    "Don Young" <> wrote in message
    news:...
    >
    > "Sudy Nim" <> wrote in message
    > news:ypfCi.481194$...
    > > Is it possible to run two portable generators in parallel?
    > >
    > >

    > Possible but not practical unless the generators are designed for
    > parallelling. Requires careful regulation of fuel to properly hold the
    > frequency and to share real (resistive, in phase) power load and requires
    > regulation of voltage to properly share reactive (inductive or capacitive,
    > out of phase) power loads. Otherwise the generators will "fight" each

    other
    > trying to control the frequency and voltage.
    >
    > It is much, much easier to just split the load if you want two generators.
    >
    > Don Young
    >
    >


    A big thanks to all I appreciate your sharing of knowledge. Very informative
    and I really got an education. I believe I (could) now parallel two
    generators but as I would not do this regularly it would be easy to overlook
    something and open myself to injury or worst. I think this is a subject for
    someone that is going to set up a continuously operating source of power?
    When my power goes out especially in a rain storm, I am often in the dark
    and irritated, not thinking properly, rushed to get the sump pumps running;
    it is not the correct attitude or environment for taking on a project
    requiring caution. Just setting up and operating a generator is a great
    enough task. All things considered, as I do not use the generator on a
    regular basis it would appear in my case, a bigger generator is the "proper"
    solution. Sudy Nim
    Sudy Nim, Sep 2, 2007
    #8
  9. In article <>,
    Dale E <> wrote:

    > How do the genny's maintain sync?


    with either, a very expensive Electronic Governers, or they don't, and
    things get very intersting, very fast, and the Magic Smoke appears.
    Mechanical Governers found in small and medium sized (Typically less
    than 100Kw) Gensets are NOT going to be good enough to keep the Magic
    smoke from appearing...... if you need more power than you can get out
    of your small genset, then you just need a BIGGER Genset, unless
    you got an Inverter Based Genset, that is designed for Paralleling.

    Bruce in alaska
    --
    add a <2> before @
    Bruce in Alaska, Sep 2, 2007
    #9
  10. Sudy Nim

    NotMe Guest

    "Ulysses" </> wrote in message
    news:...
    |
    | "Sudy Nim" <> wrote in message
    | news:ypfCi.481194$...
    | > Is it possible to run two portable generators in parallel?
    | >
    | >
    |
    | Aside from buy two new inverter generators designed to be paralleled I've
    | read (in this NG) in the past about using a 100 watt light bulb to somehow
    | synchronize the waveforms. From what I've read it's tricky but can be
    done,
    | at least sometimes. I imagine the frequency needs to be very close on
    both
    | gennies. Perhaps some googling might turn up some old posts on the
    subject.

    The process is very simple.

    The bulb is wired to the hot line of both gen sets. The speed and voltage
    are adjusted so the bulb is effectively 'off'.

    When the genset are more then 20 Hz off the bulb is constant on, as the
    frequency approaches a match the bulb flickers until full frequency and
    phase is in sync. At full voltage and freq sync the bulb is off.

    To my personal knowledge (goes back 50+ years) this process was and may
    still be used in marine applications when hot transferring loads from a
    running genset to another gen set when the first is to be shut down for what
    ever reason.

    I've also observed (but have zero personal experience other than watching
    the deed be done) the process used to sync gen sets that had the ability to
    self maintain sync over narrow ranges once set up.
    NotMe, Sep 3, 2007
    #10
  11. The message <>
    from Dale E <> contains these words:



    > Johnny B Good wrote:
    > > The message <>
    > > from Dale E <> contains these words:
    > >
    > >
    > >
    > >
    > >>sylvan butler wrote:

    > >
    > >
    > >>>On Sat, 01 Sep 2007 21:45:56 GMT, Sudy Nim <> wrote:
    > >>>
    > >>>
    > >>>>Could you point me to someplace to get a little info? I realize that two
    > >>>>generators need to be timed together and of equal output and balanced in
    > >>>>some way. If it were too expensive or complicated I would just
    > >>>>take a pass
    > >>>>to something simpler.
    > >>>



    > >>How do the genny's maintain sync?

    > >
    > >
    > > In exactly the same way that the large PSU's generators (national grid
    > > connected power station generators) do.
    > >
    > > A synchronous AC motor is essentially the same as an AC generator
    > > (excepting the obvious starting/control gear differences). Once a
    > > generator set (steam or gas turbine powered) is up to speed and in phase
    > > with the grid, it can be connected to the power station's transformer
    > > bus. Thereafter, the more steam or throttle it is given the harder it
    > > will 'push' (production of amps into the load which boosts the grid
    > > supply - i.e. exporting electrical power).
    > >
    > > However, if the steam or fuel is throttled back, the generator will
    > > remain in sync by using power from the grid (it will then act as a
    > > synchronous motor). The effect will be to increase the load on the
    > > remaining generator sets connected to the grid which will cause them to
    > > slow down a little as well as cause the grid supply voltage to droop a
    > > little (which will reduce the amount of power taken by the load on the
    > > grid by a similar fraction - assuming the major load does not comprise
    > > wholly of SMPSU powered devices :).
    > >
    > > In a 'national grid' setup, there are various classes of power
    > > stations, amongst which will be main stations which will adjust their
    > > power delivery by increasing or decreasing their generator set speed
    > > from a a national time standard derived 50 or 60 Hz reference so as to
    > > average exactly a 50 or 60Hz frequency over each (and every) 24 hour
    > > period. The adjustments appear to be applied at about 4 per minute.
    > >
    > > The rest of the power generating plant connected to the grid will
    > > simply remain in sync following the changes of frequency being imposed
    > > by the main station(s).
    > >
    > > In any decent sized grid system, it's unlikely that the largest
    > > generator in a main power station will be called upon to provide more
    > > than 5% of the total load on the grid (more likely less than 1%) so the
    > > problem of dealing with the effect of an outage of prime motive power in
    > > a generator set on the rest of the grid (loss of steam delivery or blown
    > > turbine casing, or whatever) is much less than in the case of a two
    > > generator home power setup.
    > >
    > > Here (dual generator home power setup), each generator will probably
    > > only have a 60 or 70% capacity of the total load. An outage of one of
    > > the generators will almost certainly shutdown the other due to overload
    > > (unless the load just happens to already be within the capacity of the
    > > remaining generator). Essentially, a dual generator home power setup
    > > simply lacks the 'redundency' that's built into the national grid setup.
    > >
    > > If you're planning on a home power multi generator system, you need at
    > > least 3 generator sets to gain a reasonable benefit in terms of
    > > reliability of supply. In this case, ideally, each generator will be
    > > rated for one third of the absolute maximum load and have a short term
    > > (5 or 10 minutes?) overload capacity of 50% above their maximum
    > > continuous rating (as well as the obvious extra synchronising control
    > > gear to permit such combining onto a common supply busbar).
    > >
    > > As has already been pointed out, it's probably best to keep the two
    > > generator loads seperate rather than combine them. Here, you might
    > > seperate the loads into critical and optional loads with a swap over
    > > switch between the generators and their loads (perhaps using an
    > > automated relay operated swap over switch designed to give priority to
    > > the critical load so that it remains connected to a working generator
    > > regardless of whichever fails - or is shutdown).
    > >
    > > One major consideration with seperately loaded generators is the issue
    > > of safety. This arises whenever there is the possibility of the two hot
    > > phase voltages being present within arm's reach of each other.
    > >
    > > Since the generators are both free running and, for safety's sake, have
    > > a common 'neutral' and ground connection, the hot phase voltages will be
    > > going in and out of phase. This means, (in the extreme case of identical
    > > voltage magnitude) that the voltage difference between the two phases
    > > will vary from zero voltage to double the generator voltage at the
    > > difference frequency (maybe as low as half a Hertz or less) which makes
    > > the shock hazard even more lethal than in the single generator
    > > situation.
    > >
    > > Provided this potential hazard when running two generators into
    > > seperate loads is taken care of, this method offers a better solution to
    > > the combined into a single load method (unless you're prepared to invest
    > > in generator sets with at least a short term rating equal to the total
    > > maximum load - i.e. bigger, more expensive generators).
    > >


    > I'm not the O.P. but I think he will find your reply as informative as
    > I did. Thanks.


    Well, Dale, it's nice of you to say so but, in view of Bruce's comments
    re 'The Magic Smoke'(tm), I feel obliged to point out that the
    generator's circuit breakers should take care of that little problem.

    Ideally, both generator sets should be free running within a fraction
    of a percent of each other's speed to avoid load hogging by the faster
    set. Even so, provided this speed difference is sufficiently small, the
    load sharing imbalance will also be sufficiently low enough not to
    matter.

    If you're running two sets to provide for intermittent peak demand
    loads then even in the extreme case of one set running out of fuel
    during a period of low electrical demand, the fuel starved generator
    will keep right on running (the generator now acting as a synchronous
    motor) provided the total load on the remaining set is still within its
    rating.

    Spinning a fuel starved generator set via the electrical link from the
    remaining set can present a considerable load (ICE pumping losses at
    1500/1800 rpm if the throttle is left wide open on a petroleum or gas
    powered 4 stroke engine - not so bad if the throttle is closed - a
    diesel engine doesn't normally incorporate any induction throttling).

    Generator sets designed to be 'ganged' in this fashion may well
    incorporate a 'freewheel' drive between the prime motive power source
    and the alternator to avoid imposing the extra mechanical loading under
    such conditions (although a solenoid operated contactor driven by
    suitable monitoring/control electronics can achieve the same effect,
    only better - eliminating the windage losses in the alternator itself as
    well).

    Whilst the concept of combining the power output of two or more
    modestly rated generators onto a single higher power bus (a sort of
    'Redundent Array of Inexpensive Generator Sets' as it were) to emulate a
    'mini national grid' might seem appealing, it does have a serious
    shortcoming compared to the model it has been scaled down from.

    The variations of demand on the national grid (in percentage terms) are
    a hell of a lot smoother than those imposed on a home generator system
    designed to substitute the mains supply and satisfy the normal peak
    demands. The PSU might see a 30% rise in demand over a twenty second
    period as TV viewers take advantage of an advert break to boil a kettle
    of water for a hot beverage.

    If the PSU has access to pumped storage backup, the ten seconds run up
    of the 'hot standby' genset backed up by the 60 second runup from
    standstill gensets will easily cover the peak demand. Even if there is a
    shortfall, the grid voltage will simply sag a little until the extra
    capacity comes on line to match the demand.

    A home setup has no such resiliency. the demand can go from, say, 1.5KW
    to 3.5KW in the blink of an eye and can then jump to a 5.5KW loading
    within a second or two of that first increase. If you have installed a
    pair of 3.6KW gensets which can be ganged onto the main house supply bus
    and are running just the one to minimise fuel consumption, the second
    loading event will have tripped out the generator before you could even
    start the other genset, let alone bring it up to speed and phase to
    allow its connection onto the house bus.

    If you are going to run two or more ganged gensets, you will need to
    keep them all running during the outage unless you are prepared to
    follow a strict plan on electrical usage - effectively booking the extra
    capacity ahead of the actual demand.

    The resulting fuel consumption under light loading of say a pair of
    3.6KW rated gensets is likely to be higher than for a single 8KW genset
    under the same load. IOW, the running costs will be very nearly the same
    between the two options (One large generator versus two or more smaller
    generators).

    On balance, the use of two or more small gensets as a substitute for a
    single larger capacity unit is best served by having split power buses
    rather than trying to combine the output onto a single bus. You have the
    benefit of redundency and a foolproof system of prebooking capacity for
    the extra transient loads.

    There is a way to combine two or three smaller gensets economically
    onto a single bus without the risk of overloading the single running
    genset by the switching of additional loads. Essentially this makes use
    of a battery powered inverter capable of making up the shortfall during
    the runup time required to bring the extra genset on line. The inverter
    needs to be of the type designed to allow export of surplus power back
    to the grid. This not a cheap solution considering that we might need
    some 3 to 6 KW of inverter capacity and involves a relatively expensive
    consumable in the form of a heavy duty rechargable battery pack.

    If you're looking at a strategy to minimise the effects of extended
    mains supply outages (hours to days worth), the two differently sized
    generator sets on seperate buses supplemented by suitable UPSes to
    protect PCs and similarly microprocessor controlled devices is going to
    be the most cost effective and simplest solution to implement.

    Such a system will require you to manage your electrical demands to
    avoid overloading your generator capacity, but this will be a relatively
    minor inconvenience compared to the alternative of having no electrical
    loads at all to be managed.

    --
    Regards, John.

    Please remove the "ohggcyht" before replying.
    The address has been munged to reject Spam-bots.
    Johnny B Good, Sep 3, 2007
    #11
  12. On Sun, 02 Sep 2007 20:02:19 GMT, Bruce in Alaska <> wrote:
    > In article <>,
    > Dale E <> wrote:
    >
    >> How do the genny's maintain sync?

    >
    > with either, a very expensive Electronic Governers, or they don't, and
    > things get very intersting, very fast, and the Magic Smoke appears.


    Not true. In fact, you do NOT WANT ELECTRONICS involved unless they are
    "very expensive" because simple mechanical governors will work fine. If
    one genny tries to go faster, it will naturally be loaded more heavily
    and this will tend to slow it down. (Called load hogging.)

    sdb
    --
    What's seen on your screen? http://PcScreenWatch.com
    sdbuse1 on mailhost bigfoot.com
    sylvan butler, Sep 3, 2007
    #12
  13. On Sun, 02 Sep 2007 19:37:06 GMT, Sudy Nim <> wrote:
    > enough task. All things considered, as I do not use the generator on a
    > regular basis it would appear in my case, a bigger generator is the "proper"
    > solution. Sudy Nim


    Smart choice. The only other real consideration would be the inverter
    with generator assist. More expensive. But capable of so much more.
    :)

    sdb

    --
    What's seen on your screen? http://PcScreenWatch.com
    sdbuse1 on mailhost bigfoot.com
    sylvan butler, Sep 3, 2007
    #13
  14. Sudy Nim

    Guest

    daestrom <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:

    >While at school, a student paralleled two 'small' 5kW units together close
    >to 180 out. These were actually MG-sets used for training where a DC motor
    >was used to drive the AC generator.


    When I shorted the output of a 20 HP AC MG set at school, it didn't rip off
    the foundation, but it blew a circuit breaker 3 buildings away :)

    My ME brother used to test 3' diameter pressure-film lubricated bearings
    at GE in Schenectady, 20,000 horsepower and up. It must be exciting when
    one of those seizes on a 300' shaft.

    Nick
    , Sep 3, 2007
    #14
  15. Sudy Nim

    Ray King Guest

    A few years ago I had a meeting at Siemens/ Orlando. The division that
    supplies grid connections for the various power grids in the USA. They had
    one long wall that was the map of the USA showing the grids and where the
    were connected. They supplied two types of grid connectors. One which
    connected any voltage with any voltage at any phase angle. ( This rectifies
    each grid to supply current to a common dc buss. Then used an inverter to
    produce ac at any voltage or frequency or phase to the needed ac grid ) (
    the rectifier is really an inverter ) A large watt hour meter sat on the dc
    buss reading the dc buss voltage and recording which direction the dc
    current was flowing from. The dc buss was supplied from one ac or the other
    ac buss. depending who needed energy. The second type of ac buss connector
    had to adjust the ac voltage of one ac buss to mirror the other ac voltage
    buss ( using tapped transformers). The frequency is held in synchronization
    which may take several days to match long before a connection is needed. A
    reactive component is added in series with the grid switch until the phases
    were locked together. This reduces the high currents caused by even the
    slightest phase imbalance.
    The second system seems closer to the issues of paralleling small
    generators.

    Ray






    "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
    news:46dc280d$0$15407$...
    >
    > "Sudy Nim" <> wrote in message
    > news:ChECi.484863$...
    >>

    > <snip>
    >>
    >> A big thanks to all I appreciate your sharing of knowledge. Very
    >> informative
    >> and I really got an education. I believe I (could) now parallel two
    >> generators but as I would not do this regularly it would be easy to
    >> overlook
    >> something and open myself to injury or worst. I think this is a subject
    >> for
    >> someone that is going to set up a continuously operating source of power?
    >> When my power goes out especially in a rain storm, I am often in the dark
    >> and irritated, not thinking properly, rushed to get the sump pumps
    >> running;
    >> it is not the correct attitude or environment for taking on a project
    >> requiring caution. Just setting up and operating a generator is a great
    >> enough task. All things considered, as I do not use the generator on a
    >> regular basis it would appear in my case, a bigger generator is the
    >> "proper"
    >> solution. Sudy Nim
    >>

    >
    > While I agree with your decision, the pros don't have any special
    > advantage when it comes to paralleling generators. A good base-load nuc
    > power plant might synch to the grid once a year or less. With ten or
    > twelve different operators rotating shifts, the individual that synchs-in
    > next time may not have done it for several years. And there's always a
    > first time for the new guy.
    >
    > The trick is to write down exactly what you should do, in the order that
    > you should do it. Then, when the time comes, follow your procedure and
    > read the steps. Even make a check-mark by each step as you perform it if
    > it will help you keep track of what step you're on (thank goodness airline
    > pilots do this).
    >
    > Yes, some of us 'old-timers' can do it in the dark, standing on our head,
    > with one hand tied behind our back. But the good ones still use a
    > check-list (did you remember to cut-in the generator cooler? how about the
    > day-tank level?). Train yourself to use the check-list every time, even
    > in an emergency, and the 'magic smoke' will stay where it belongs.
    >
    > daestrom
    >
    Ray King, Sep 3, 2007
    #15
  16. Sudy Nim

    Sudy Nim Guest

    "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
    news:46dc280d$0$15407$...
    >
    > "Sudy Nim" <> wrote in message
    > news:ChECi.484863$...
    > >

    > <snip>
    > >
    > > A big thanks to all I appreciate your sharing of knowledge. Very
    > > informative
    > > and I really got an education. I believe I (could) now parallel two
    > > generators but as I would not do this regularly it would be easy to
    > > overlook
    > > something and open myself to injury or worst. I think this is a subject
    > > for
    > > someone that is going to set up a continuously operating source of

    power?
    > > When my power goes out especially in a rain storm, I am often in the

    dark
    > > and irritated, not thinking properly, rushed to get the sump pumps
    > > running;
    > > it is not the correct attitude or environment for taking on a project
    > > requiring caution. Just setting up and operating a generator is a great
    > > enough task. All things considered, as I do not use the generator on a
    > > regular basis it would appear in my case, a bigger generator is the
    > > "proper"
    > > solution. Sudy Nim
    > >

    >
    > While I agree with your decision, the pros don't have any special

    advantage
    > when it comes to paralleling generators. A good base-load nuc power plant
    > might synch to the grid once a year or less. With ten or twelve different
    > operators rotating shifts, the individual that synchs-in next time may not
    > have done it for several years. And there's always a first time for the

    new
    > guy.
    >
    > The trick is to write down exactly what you should do, in the order that

    you
    > should do it. Then, when the time comes, follow your procedure and read

    the
    > steps. Even make a check-mark by each step as you perform it if it will
    > help you keep track of what step you're on (thank goodness airline pilots

    do
    > this).
    >
    > Yes, some of us 'old-timers' can do it in the dark, standing on our head,
    > with one hand tied behind our back. But the good ones still use a
    > check-list (did you remember to cut-in the generator cooler? how about the
    > day-tank level?). Train yourself to use the check-list every time, even

    in
    > an emergency, and the 'magic smoke' will stay where it belongs.
    >
    > daestrom
    >


    Daestrom I agree with your statement 100%. I did not set up a check-mark
    list but I do have a step by step procedure. Step 1- check oil level, et-
    cetera with pictures of item and its location. I had the pages laminated and
    attached to the generator so I can readily find a copy. I did two
    instruction pages one for start up another for shut down. Before the written
    procedure AND pictures I have stared at the generator and wondered where is
    the run switch? I like your idea of that check-mark list which I am working
    on now.
    Sudy Nim, Sep 3, 2007
    #16
  17. In article <46dc2f88$0$32494$>,
    "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:

    > While at school, a student paralleled two 'small' 5kW units together close
    > to 180 out. These were actually MG-sets used for training where a DC motor
    > was used to drive the AC generator.
    >
    > Even that 'small' unit managed to rip itself from the foundation bolting and
    > roll over through a cinder-block wall. This was despite there being the
    > usual amount of protective relaying on the units (typical reverse-power,
    > over-current, phase-failure, etc...) Needless to say, the class was
    > canceled for the rest of the day.
    >
    > Yes, the torsional forces created can be 'considerable'.
    >
    > daestrom
    > P.S. No, it wasn't me :)


    It would be interesting to see all these "Experts" take the challange of
    their nearest University's Electrical Engineering Motor/Generator &
    Control Lab, for just an afternoon. I wonder if it is still a Required
    Course for UnderGraduates.

    Bruce in alaska
    --
    add a <2> before @
    Bruce in Alaska, Sep 3, 2007
    #17
  18. Sudy Nim

    Sudy Nim Guest

    "Ulysses" </> wrote in message
    news:...
    >
    > "Sudy Nim" <> wrote in message
    > news:ChECi.484863$...
    > >
    > > "Don Young" <> wrote in message
    > > news:...
    > > >
    > > > "Sudy Nim" <> wrote in message
    > > > news:ypfCi.481194$...
    > > > > Is it possible to run two portable generators in parallel?
    > > > >
    > > > >
    > > > Possible but not practical unless the generators are designed for
    > > > parallelling. Requires careful regulation of fuel to properly hold the
    > > > frequency and to share real (resistive, in phase) power load and

    > requires
    > > > regulation of voltage to properly share reactive (inductive or

    > capacitive,
    > > > out of phase) power loads. Otherwise the generators will "fight" each

    > > other
    > > > trying to control the frequency and voltage.
    > > >
    > > > It is much, much easier to just split the load if you want two

    > generators.
    > > >
    > > > Don Young
    > > >
    > > >

    > >
    > > A big thanks to all I appreciate your sharing of knowledge. Very

    > informative
    > > and I really got an education. I believe I (could) now parallel two
    > > generators but as I would not do this regularly it would be easy to

    > overlook
    > > something and open myself to injury or worst. I think this is a subject

    > for
    > > someone that is going to set up a continuously operating source of

    power?
    > > When my power goes out especially in a rain storm, I am often in the

    dark
    > > and irritated, not thinking properly, rushed to get the sump pumps

    > running;
    > > it is not the correct attitude or environment for taking on a project
    > > requiring caution. Just setting up and operating a generator is a great
    > > enough task. All things considered, as I do not use the generator on a
    > > regular basis it would appear in my case, a bigger generator is the

    > "proper"
    > > solution. Sudy Nim
    > >
    > >

    > Another consideration, as someone else pointed out, would be to get an
    > inverter that is designed to sync with a generator such as a Xantrax/Trace
    > SW series. From what I have read the output power from the two sources

    can
    > be combined for a total greater output. I have OutBack inverters and they
    > do not have this feature.
    >
    > Many (or most) of us here use a large battery bank and inverters for our
    > main power supply. The batteries are charged via solar panels, wind
    > generators, or generators with various battery chargers. The result is a
    > pretty-much-uninterupted power supply with (assuming you have a good
    > inverter) high quality output. Personally I mainly use my generator only
    > for charging my battery bank but sometimes I'll use it to run a heavy load
    > for a short time (such as an air compressor) just because it's more
    > efficient for me to do it that way.
    >
    > It's possible to start out fairly small with a battery/inverter systems if
    > you can manage your loads but old batteries do not usually mix well with

    new
    > batteries so it's generally better to figure out how much battery power

    you
    > need in advance and just get the bigger battery bank. I got by for years
    > with four 6 volt golf cart batteries, a $100 inverter, and a 2000 watt
    > generator. I did, however, need a 5000 watt generator for about 15-30
    > minutes a day to pump water and run my compressor.
    >
    >

    Must admit my lack of knowledge when it comes to inverters. Don't know that
    I ever saw one. I have looked into getting a larger generator but the next
    size up (to power an air conditioner) is really too big. At the moment my
    4000-watt is convenient and adequate for nearly all my needs. It will easily
    handle lights, water, refrigerator, TV and furnace in the winter only
    lacking that occasional "cooling" option in the summer. Not sure what I will
    do yet. Thanks for the inverter update; I will do a search to check it out.
    Sudy Nim
    Sudy Nim, Sep 5, 2007
    #18
  19. Sudy Nim

    Vaughn Simon Guest

    "Sudy Nim" <> wrote in message
    news:QypDi.491695$...
    >
    > Must admit my lack of knowledge when it comes to inverters. Don't know that
    > I ever saw one. I have looked into getting a larger generator but the next
    > size up (to power an air conditioner) is really too big. At the moment my
    > 4000-watt is convenient and adequate for nearly all my needs. It will easily
    > handle lights, water, refrigerator, TV and furnace in the winter only
    > lacking that occasional "cooling" option in the summer. Not sure what I will
    > do yet.


    What many Floridians do is buy a cheap window unit and just keep it on a
    shelf. Your 4000-watt generator will start & run at least a 5000 (and probably
    an 8000) BTU unit which you could use to create a "cool room". It is also
    useful if your central AC unit goes out.

    Vaughn
    Vaughn Simon, Sep 5, 2007
    #19
  20. Sudy Nim

    Sudy Nim Guest

    "Vaughn Simon" <> wrote in message
    news:zcvDi.492461$...
    >
    > "Sudy Nim" <> wrote in message
    > news:QypDi.491695$...
    > >
    > > Must admit my lack of knowledge when it comes to inverters. Don't know

    that
    > > I ever saw one. I have looked into getting a larger generator but the

    next
    > > size up (to power an air conditioner) is really too big. At the moment

    my
    > > 4000-watt is convenient and adequate for nearly all my needs. It will

    easily
    > > handle lights, water, refrigerator, TV and furnace in the winter only
    > > lacking that occasional "cooling" option in the summer. Not sure what I

    will
    > > do yet.

    >
    > What many Floridians do is buy a cheap window unit and just keep it on

    a
    > shelf. Your 4000-watt generator will start & run at least a 5000 (and

    probably
    > an 8000) BTU unit which you could use to create a "cool room". It is also
    > useful if your central AC unit goes out.
    >
    > Vaughn
    >
    >

    Thank you Vaughn. That's a suggestion I can easily live with. Sudy Nim
    Sudy Nim, Sep 5, 2007
    #20
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