Shopping Guidelines

If you are not going to use all the volts allowed by a Grid tie inverter immediately, can you convert the amps and volts , like 10A@12Volts is the same as 5A @24 volts. to raise the allowed amps for the inverter, or would you just have to get a new one afterwords? out of warranty?
Always troubleshoot with adequate sunlight.  Hi Ho Hi Ho
2.3kW [10] Enecsys SMI-240-60 micro inverters

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Shopping Guidelines

    You are mixing technologies (pure GT, battery based/backed GT) and units of power, energy, other units (volts, amps). In general, Inverters are "constant power" devices... So, within the operational range of the inverter, the equation of Power=Volts*Amps applies. If the input voltage goes higher, the input current falls, etc...

    Without understanding your exact requirements/setup, it is difficult to give you an accurate (and safe) answer.

    Pure Grid Tied Inverters (no batteries) are well known, understood, and safe. And (usually) the most cost effective solution for generating "home power".

    However, not all utilities support Grid Tied connections, plus going "legal" GT requires permits and, usually, a licensed electrician to install (that does not always work out either).

    You can go with Hybrid Inverters that support batteries plus Off-Grid and GT operation--and even possibly support installation/operation with utilities that do not allow GT inverters to back feed the grid (run meter backwards). But, obviously, this is more expensive, more complex, and sometimes skirts rules/regulations (again, depending on utility/country).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Thomas
    Thomas Solar Expert Posts: 291
    Re: Shopping Guidelines

    Can you co the other way with it though, increase the amps past the rating if you are below the max volt rating?
    why is there a signifigant difference between gt/ battery backed/ off grid? My budget hybrid does batteries but no off grid.(at all)
    the reason I ask is my inverter seems to need updating, and the cost is prohibitive, to say the least.
    All of the next level inverters I have looked at are all based on systems that are 24v or higher, and thus their amp rating is low.
    I guess I would have to have more expirience to know what engineering would allow for that and what wouldn't.(by model, etc)
    I started shopping around for a grid tie and all I found were like 10-20 amp models. My panels are allready at that limit albiet 12v.
    anyway it is gonna take some money I do not have so all of this is hypothetical, i will keep looking for a GT inverter, preferably w/battery back-up for nighttime use, I think a safe middle of the road approach to the meter spinning backward issue for a while is to just match it if you can . My power company does support it, kinda like the way I read about getting taxed at the end of the year or not. I believe.
    Another observation why is SSW under so much fire? Like my poor Hybrid GT?Anyway WOW>:p
    Always troubleshoot with adequate sunlight.  Hi Ho Hi Ho
    2.3kW [10] Enecsys SMI-240-60 micro inverters

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Shopping Guidelines

    The whole question of cheap GT/OG/Hybrid inverters... There is not much profit margin in small inverters, so desinging/obtaining UL/NRTL for various countries is not really worth it. And for folks buying new on EBay, customers being "cost sensitive" drives the margins down even more. Which many companies, seem to believe, justifies reducing quality and writing specifications that are (frequently) not worth the bits sent across the Internet.

    The whole question of current... I am not understanding if you are talking about input or output current. For example a 3kW GT inverter with ~ 3.5 kW array driving into a typical 230 VAC circuit will output:
    • Power = Volts * Amps -- Or
    • Amps = Power / Volts
    • 3,000 watts / 240 VAC = 12.5 amps -- not very much "current" at all
    However, the same 3kW inverter, if powered by "12 volt" battery bank will require as an input current:
    • 3,000 watts * 1/0.85 inverter eff * 1/10.5 volts cutoff = 336 amps -- A huge amount of current at any voltage
    So, as you flip voltages 12/24/etc. and 120/240, talking about the size of the GT/OG/Hybrid inverter gets real confusing real fast.

    In general, it is cheaper to work with higher voltages rather than higher currents (up to a point). And, when you want to have a larger system, you hit those "current" limits very quickly--And usually you are almost forced to go to a higher DC Battery Bank (or Vmp-array) to support the larger power needs while keeping the current levels "reasonable".

    Also--Way back, did you not say you were building your own solar panels? If so--For Grid Connected / GT systems, most building/fire codes will not allow DIY panels--You have to use UL/NRTL Listed panels for such an installation.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Thomas
    Thomas Solar Expert Posts: 291
    Re: Shopping Guidelines

    My homeade panel flopped, no amps and 19volts
    I was talking about input/array side
    I would use/need 110 here in a Amp Service mobile home park.
    I am prety sure of mathing amps with my load is going to be a good enough forecaster of performaqnce.
    I think mixing up that formula way too much bridging across that operand of multiplier or divisor way too cavalierly is the reason for my pains!!!
    Lately with the addition/question of 24 volt, I seem to be attempting to play w/it some...
    I use to have a habit in College of playing with Standard deviation and Variance differences similarly, bad habits are...at least I don't smoke anymore.(over a year and a half now)quit beef toooo[5 years],and beer[alchohol 3 years],,,reasons for my pain...and genset.
    Always troubleshoot with adequate sunlight.  Hi Ho Hi Ho
    2.3kW [10] Enecsys SMI-240-60 micro inverters

  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    Re: Shopping Guidelines

    The main problem here is you didn,t want to listen to anyones advice. Most members here like to help new people learn and mostly give good advice. Once in a while we have new members come along and won,t listen or accept others advice. They try to make thier own panels and use unauthorized equipment and learn after they waste a lot of money that they should have listened. Also they don,t want to do the proper and legal redtape and inspections. Did you figure the total cost of you making a panel? There are still good approved panels for sale that are just over $1.00 per watt that have a warranty and you can get top rated brands for just a little over $1.50 per watt. If you don,t have a lot of money to start your solar system here is a good economical GTI inverter that I have seen for sale for a reasonable price. Do your searching and you will find a big gap in the selling price. A Fronius IG-2000 is a good starter inverter as it is reasonable price and can run with less solar panels than some. Mpp voltage range 150 to 400 vdc. maximum output is 2000kw. @ 8.35 amp 240 vac. I started with this inverter with 14 158 watt kyocera Kc 158 g panels which was the limit and another fronius ig-3000 inverter. I took the Ig-2000 out of service as I had 2 extra panels I couldn,t use and bought the newer fronius IG-plus 3000 so i could use the extra 2 panels I have. Not using the ig-2000 inverter presently and would sell it for $1000.00 as I would like to get another IG plus 3000 watt inverter. The IG inverters max imput voltage is 500 vdc where as the plus models max imput is 600 vdc. The Ig- 2000 model is better to use on smaller solar arrays as it will turn on at 150 vdc. The plus models need 230 vdc to turn on. My ig 2000 always goes online first in the morning. This reply is not to be hurtful in any way, just good advice. I held back at first because the redtape seemed too daunting. Finally one day I called the power co to find what I needed to do. One thing I can say they can hold you up for awhile just like dealing with the government. I started the paper trail in June and got online DEC 24 th. I needed to get the instalation done for income tax purposes as I was retireing the next year. Glad I did mine the legal way and I had only $10 monthly electric bills for the last year. If you can swing it, try to get enough panels to fill up the inverter. The problem I had was I bought my panels at different times so had to get 1 inverter for 1 string of panels and another inverter for other string. The companys keep making new models of panels and then you can,t find ones to match the ones you have. solarvic
  • Thomas
    Thomas Solar Expert Posts: 291
    Re: Shopping Guidelines

    I tried to make my own panel and ended up buying some instead.
    contrary to the general mood I gather from this forum, I am glad I did install all of this correctly, It was worth it to try and stay Wholly O.E.M. D.I.Y. and not fractionalize the entire effort into a huge eye-sore, well within my potential!
    so was the functional array I now have, no matter how basic it is, which was also well within my potential probobility at inception of this project back in 2007
    I think I may have expected the forum to automatically know what I was talking about...
    I had 3 40 watt panels kicking around for years, a wind generator, and I bought parts for it as I could afford...
    A continueing adjustment from this forum is there is a lot more to it and a lot more to go. Again, I am relieved I actually did install everything correctly, solar can be gimmicky/gagdety as well as utility.
    Barring any real misfortune I am done with this project now for the summer, ecept maybee some more 12volt panels.
    I would love to buy a GTI for that money but I truly need to learn something about 24volt three digit volts. before I change over to 24 volts I want to get to 500-750 watts@ 12v I think a reasonable limit for me. REM I do not have or use resistive or overly inductive loads.
    I am going to post some pictures as soon as I can for the summer...[spring]
    I deleted this first quick reply by accident, this is a paraphrase of a improvised response, however thoughtful of my very own....
    Always troubleshoot with adequate sunlight.  Hi Ho Hi Ho
    2.3kW [10] Enecsys SMI-240-60 micro inverters

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Shopping Guidelines
    Again, I am relieved I actually did install everything correctly,

    Thomas,, I don't mean to be the voice of doom over and over again,, but I would contend, that after having discussions with you on a number of threads, where you revealed you lack of understanding about proper grounding design and method, (Not to mention your installation method of your "grid tie inverter" in blow in insulation, that you most probably have not installed "everything correctly"! Sorry!
  • Thomas
    Thomas Solar Expert Posts: 291
    Re: Shopping Guidelines

    Apology accepted!
    I am over insulated and over grounded.
    850 kwhrs 85 by the power co.
    950 from the panel
    100 down time
    Always troubleshoot with adequate sunlight.  Hi Ho Hi Ho
    2.3kW [10] Enecsys SMI-240-60 micro inverters