Can a GT inverter be "tricked" to work when there is no grid?

jeffkrusejeffkruse Posts: 205Solar Expert ✭✭✭
My friend has a Sunny Boy GT inverter 4K. He wants to know if it can be "tricked" to provide power when the grid is not connected. Could it be as simple as connecting a 60Hz 120V function generator to the inverter?

Comments

  • solarteksolartek Posts: 69Solar Expert ✭✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    First of all, the Sunny Boy 4000US is a 240V inverter. But go ahead and hook up a 240V 60Hz function generator and then stand back to watch the "magic smoke" come out of it. ;)

    No this won't work.

    Scott.
  • halfcrazyhalfcrazy Posts: 717Solar Expert ✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    yep it can be tricked into turning on but you will need a magic boxed called a "Sunny Island"
  • stephendvstephendv Posts: 1,571Solar Expert
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    If I remember correctly the Sunny Boy does 3 checks to determine whether there's a grid connected or not: Voltage, frequency and impedence. If you set the sunny boy up to work in off-grid mode, then it won't do the impedence check, but will still need a voltage and frequency to latch on to.
    You don't strictly need a sunny island, but you will need something that generates the right voltage and frequency - and you'll have to find some other way of controlling excess power in the AC bus.
    What the sunny island does is control the amount of power the sunny boy outputs by increasing the mini-grid frequency. There is no dedicated communications link between the sunny island and sunny boy, all it uses is the grid frequency.
  • BB.BB. Posts: 27,898Super Moderators, Administrators admin
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    With US based GT inverters... You can setup a off-grid "master" True Sine Wave inverter to "provide the grid" and then attach a GT inverter to follow the "master" off-grid inverter.

    If the GT is providing less power than load, both inverters will share.

    If the GT is supplying more than the load--the off-grid inverter will actually start charging the batteries.

    Hence the "issues". 1. the off-grid inverter is not designed to "run backwards" and 2. the battery charging is "uncontrolled" (battery bank can be overcharged and cause damage--or possibly even fire/explosion).

    Setting up a battery charge controller can be done (diversion controller, interrupt the GT AC output, etc.--possibly a pair of independent charge controllers for safety sake).

    I believe Germany has a Network Impedence Test requirement--I have not seen any such requirement for a US/North American GT inverter.

    Solar Guppy would be a much better person to address those issues than I...

    Jeffkruse,

    Do you want to continue down this discussion path? Or is this enough information for now.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • GreenerPowerGreenerPower Posts: 264Solar Expert ✭✭✭✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    Not sure how much regulation is in PR, keep in mind that your "power island" needs to be disconnected from the main line. Otherwise the local utility transformer might electrocute people servicing the power outage.
    GP
  • jeffkrusejeffkruse Posts: 205Solar Expert ✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    Thanks for all the replys. What is a Sunny Island and how much does it cost? He has 18 205W Evergreen pannels. He spent all his money on this setup but he doesnt have backup power in the event of a huricane.

    Yes, He would completely disconect his system from the grid if he were to use a Sunny Island.

    Thanks,

    Jeff
  • halfcrazyhalfcrazy Posts: 717Solar Expert ✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    Sunny Island is an off grid inverter made by the same company so he would need one of them and batteries and the stystem networks and works as you describe flawlessly and there is no need to unhook anything from the grid it does it automatically
  • jeffkrusejeffkruse Posts: 205Solar Expert ✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    Oh, I was thinking a "Sunny Island" was an inexpensive "box" that you could connect to the Sunny Boy and use it for off-grid with no batteries. He would like an inexpensive way to use the power from the pannels when the grid is out for extended periods of time.

    He should have just got a Xantrex 4548 like I did ;) He would have liked to but he couldnt justify the cost of the batteries.
  • RCinFLARCinFLA Posts: 1,280Solar Expert ✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    BB. stated most of facts.

    Bottomline is the power the Grid-Tie generates has to go somewhere. If your loads are greater then power generated from grid-tie in parallel with output of off-grid, battery based inverter/charger it will work.

    If loads are lighter then GT output then power goes to battery, uncontrolled and possible overcharging batteries to point of destruction.

    Note, we are talking about a syncronous sinewave off grid inverter/ charger, not a cheap portable unit, sinewave or modified sinewave, that runs from a 12v or 24v battery. These inverters will not pump power back to battery if syncronized A.C. power is injected back into to AC output plug.

    Same applies to a gas generator used to create A.C. reference.

    No cheap and dirty way to get a GT to work offline.
  • TnAndyTnAndy Posts: 249Solar Expert ✭✭✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?
    jeffkruse wrote: »
    Oh, I was thinking a "Sunny Island" was an inexpensive "box" that you could connect to the Sunny Boy and use it for off-grid with no batteries. He would like an inexpensive way to use the power from the pannels when the grid is out for extended periods of time.

    He should have just got a Xantrex 4548 like I did ;) He would have liked to but he couldnt justify the cost of the batteries.


    AMEN said the choir !

    ;)
  • halfcrazyhalfcrazy Posts: 717Solar Expert ✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    Lots of people find themselves there they are tempted by the major cost savings doing a straight GT inverter. Then they are bummed when there 25,000 dollar system is Dead when the utility goes down.
  • solarteksolartek Posts: 69Solar Expert ✭✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?
    halfcrazy wrote: »
    Lots of people find themselves there they are tempted by the major cost savings doing a straight GT inverter. Then they are bummed when there 25,000 dollar system is Dead when the utility goes down.

    On the other hand, if you live in an area where the utility grid going down is an extremely rare event, the additional costs of a battery bank that never gets used but must eventually be replaced at least once or twice during a projected 25 year system lifespan can also be hard for some people to swallow. :D

    Scott.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    they still complain as halfcrazy said as we've seen it here enough. they want their cake and eat it too and at this point because of they're splitting hairs on the efficiency and costs and they complain that their power went down later does not make me feel sorry for them. that's the chance they took for their gt no backup system. it all depends on what it is you are trying to do with the solar for those trying to squeeze a buck will not have the power to show for it during an outage and can lose some of their money savings in wasted food from a dead refrigerator or have the expense and noise of a generator. you saved? maybe in some cases you did, but the degree of savings isn't as great as you think given the alternatives, even though rare.
  • stephendvstephendv Posts: 1,571Solar Expert
    Re: Can a GT inverter be "tricked" to work when there is no grid?
    TnAndy wrote: »
    AMEN said the choir !

    I don't think the Xantrex is such a clear choice in this case, the Sunny Island system + sunny boy seems a better solution because he primarily wants to use the system for grid feeding where the sunny boy is more appropriate (higher string voltages and better efficiency). Then for the occasional power cut he wants to use solar power (more than battery power), so he could add the smallest sunny island available such as the 2kW unit and a small battery bank. Since the GT is connected on the AC side he could have 2kW + 4kW of power on a sunny day.
  • nigtomdawnigtomdaw Posts: 705Solar Expert ✭✭
    Re: Can a GT inverter be "tricked" to work when there is no grid?

    Gee this sounds really complicated, I will probably get grid soon, in Spain thats mayanna,sp :blush: I was originally thinking cool sell my solar but Im leaning towards keeping my 2.4 kw array living energy free 230 days of the year and when my batteries need topping up just switch my 5.75 kw grid supply to AC1 of my SW3048e .No more generators and a $150 bill for AC grid supply YEARLY plus a monthly charge,

    A new 6kw generator of class will cost me as much as installing grid power but no service or break down bills and of course I can go with a much smaller battery bank to cover a poor days harvest of sun,

    Yes I cant sell my excess, but I dont know if Spain even offers grid tie, to El Campo people, but I expect if they did the cost of reports, engineers and inspections would be an absolute joy, the SpANISH have professional people like Solicitors to help you with goverment paperwork, and I dont speak Spanish, just a little Catalan:p

    Guess Im lucky grid is 150 feet away ;)

    Jo soc Nigel
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