Fronius MPP Hunting

24

Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Fronius MPP Hunting

    Actually, once you "discover" the peak power point for a specific array/combo, how much would one loose, if you "constrained" the inverter to that point. Sure it will change a bit over temperature, but overall, once you set it close, (maybe a warm weather setting and a cold weather setpoint) you might be ahead on your harvest, if the hunting stops.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    Quite a bit Mike .... Even in the same day between the morning to afternoon, the vmp will move 10%. And Being off more the 10% on the vmp can be 30%+ on harvest lost of your wrong on the high side of the curve.

    A VI curve from VOC->VMP is very steep , in @20% of the total array voltage the power goes from zero to maximum. As the voltage is pulled down from the VMP point to zero, its pretty linear, hence that's why pwm controllers work as well as they do, they are always below the arrays vmp point
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Hello,

    Thanks for all of the discussion.

    I really would like to know exactly what's failing in my Fronuis, but it is unlikely that I'll ever know if the replacement unit works. It seems unproductive to wish for that one to fail as well just to better analyze the problem.

    A few additional comments:

    I don't think that the Fronius is at a tap switch point. I base that on the fact that on the fact that I can hear a relay when the tap switches. Fronius verified that there is always a click. I don't hear a click at the 232 volts, nor at any time during the oscillation.

    The 4 arrays are all wired in parallel. So, there is no possibility to rewire them crosswise.

    Setting a fixed voltage would only deliver maximum power for one time of day. Besides, I found that, at least at mid day, I couldn't set the fixed voltage low enough to reach the MPP because of the weird limitation on settable voltage range.

    I hear you about switching to another brand of inverter. Hindsight is 20/20. I will see this through with Fronius. If the new ivnerter works, we're done. If not, I'll find an email address for someone at headquarters in Austria and try that route.

    Continuing their high level of customer support, Fronius has not told me when to expect the new inverter.

    Phooey!
    Mike
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Fronius MPP Hunting

    > Continuing their high level of customer support, Fronius has not told me when to expect the new inverter.

    You can expect a letter of "Declined", a week after the warrenty expires.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    You can cross wire, but it will require your installer to do that on the roof as sub-arrays to be split half& half ... not that big of a change a day at most
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Solar Guppy,

    I understand now. What is a lot less clear to me is what effect that that would have.

    I remember that I explored that subject with my installer some time ago when he was thinking about installing 2 inverters instead of the single Fronius. I read a white paper from Fronius about parallel strings and shading as well. I have a palm tree that will cause some shading in the winter months. I don't remember all the reasoning, but it turned out that under most of the partial shading conditions that I expect, wiring the strings in a simple stripe pattern is better than any other scheme. In only one shading condition was other wiring better, and then only marginally.

    I'll wait for the new inverter and hope that it solves my problems.

    Thanks,
    Mike
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    Your installer is not considering the irradiance and temperature difference of the two array. They are on different roofs and face different directions. This will cause the vmp of the two groups to be different and depending on the gap very well be beyond what the Fronius can handle for Mppt tracking

    If they are split so each string is half from one roof and half from the other, all four strings will have similar vmp point which is the important consideration.

    Shading will kill production, having as you do now, it will only take 2 panels shaded to knock out 1 of the 4 stings production wise, so regardless, your going to get a big hit by the palm when it starts shading things
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Solar Guppy,

    Thanks once more for taking the time to respond.

    According to the Fronius specification, it should find the MPP at anything over an input of 150 volts. The drop out at 232 volts is far above that, so either the unit is bad or Fronius lied. The new one is scheduled for installation Friday, so we should know soon.

    Thanks,
    Mike
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Hello,

    Today the replacement inverter was installed. It has the same problem.

    I found out another thing which annoys me. My installer went out to check another site that has the same type and number of panels with the same inverter. It was hunting as well.

    The measurements were taken by a relatively unskilled person so it is not clear whether the problem exactly matches mine. It was reported back to Fronius. That was 2 weeks ago and they didn't follow up by getting better measurements. Fronius elected to waste everyone's time by having a replacement installed.

    I made it clear to Fronius that I need to work on this problem with the Austrian engineers at the home office and they have agreed. I made it clear to the installer that I consider this a system problem and that I hold him responsible.

    Mike
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Fronius MPP Hunting
    mradtke wrote: »
    Today the replacement inverter was installed. It has the same problem.

    Damm ! Sorry about that. Sounds like it's the Software department. Software says Hardware. Hardware says Installer or it's Software. Is the tide high or low when it hunts ?

    Does the installer carry any other brand (like Xantrex GT series) that he could swap in as a replacement? Sweeten the deal, offer to pay the price difference and/or labor.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    Your going to have to decide if you want to be a unpaid testbed for Fronius or do you just want a properly working PV system.

    If its the later, you can simply have the installer put in a pair of Xantrex GT2.8's. They have a 193-600V voltage range and would work perfectly with the arrays you have now. no wiring changes

    Cost wise a pair of GT2.8's are similar to the Fronius 5100 you now have but IMHO you would come out much further ahead as you would have an inverter for each of the arrays ( SE/SW ), fully data-logging and web abilities and MUCH better thermal and efficiency performance and its convection, not fan cooled.

    If you stick with Fronius, you have at best an uncertain path ahead. I been down this path and at least I have found, even with a lab full of equipment, hard data showing the issues its very difficult to get the proper people involved. It is a huge amount of time invested to at BEST, just get what it should always have been, a properly functioning product. You don't have to do this, there are many other manufactures that have products that DO work.
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Hello,

    Thanks for your comments.

    I have set some rules with Fronius on what level of support I will tolerate from this point on. If they won't agree to it, I have asked my installer to replace the inverter. Unfortunately, replacing a single inverter with a pair will be a pain for him. As far as I know, the Fronius 5200 IG is the only single inverter which will match my collectors with any spare voltage tolerance under the Phoenix high summer heat conditions.

    I think that a pair of Xantrex GT2.8's is just marginal for my conditions. I think that a better choice would be two KACO 2901xi's. Even better would be a single KACO 4501xi, but they don't seem to sell it in the USA. Any comments on the KACO inverters?

    Still, the best outcome would be good cooperation from Fronius. That way I get my problem fixed and they get a better product.

    I'll report again when something changes.

    Thanks for listening and commenting,
    Mike
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Fronius MPP Hunting

    KACO ? never heard of them, if you think Fronius has good support, try KACO. Xantrex are a known Good Company.
    If I understand your initial post right, you have 2520W of panels, in 2 different arrays @ different angles. 1260W of solar is duck soup for a Xantrex 2.8 Heck - both could feed a single 2.8, as you only realize about 80% of label output. But 2 different directions would play heck with the MPPT - the inverter might hunt around, trying to figure out where the sweet spot is.
    The inverter rewire is all at ground level (or should be) the installers flunky should be able to handle that.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    your reported vmp was 232vdc , the GT2.8 works down to 193vdc

    Having a pair of inverters side-by-side is simple, all connections can come in one unit and transition to the second inverter thru the side holes. If your installer can't handle this you have other issues

    Going with yet another unproven manufacture isn't the best choice. Xantrex is number one in the US for a reason

    Here is my home system, 12kW of pv, 2 GT5.0's and a GT3.3 ... all the wiring comes into the BOS ( balance of system ) from behind for a super clean install
    Also the BOS can be raceways, for example, The AC for all the Units comes into the left most unit and thru the side goes to the other two units, similar for the PV
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Mike and Solar Guppy,

    Thanks for your advice.

    The panels are 5,040 total. Sorry if my original explanation was fuzzy.

    From what I've heard from you folks, the Xantrex is an excellent choice from all aspects except one: it is marginal for my array. I used the Xantrex calculator and see that rewiring to 2 strings of 14 modules would work for the Xantrex GT5.0. Is that a better choice?

    Thanks,
    Mike
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    For a single inverter and mixed orientations the GT5.0 should perform well, its been vetted in these configurations and proven to work. You can hookup a PC with SG-View and log to your hearts content ... after the Fronius issues you, more than most will appreciate this feature!

    The ideal setup is a pair of inverters, each for the two orientations ... but I don't see any reason the GT5.0 won't work for you setup , the mppt will be a compromise of the two arrays, but you shouldn't have helpless hunting with the Xantrex unit

    One of my GT5.0's has two stings of 15 panels ( 30 total ) of the Evergreen 190's, Outstanding performance from the Array and Inverter
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Hello,

    This is an update on what's happening with Fronius.

    Their last response to me was "As far as I know, there are no plans to for an internal fix in the immediate future."

    I asked Fronius USA to consult with their home office (Austria). I asked them several times since then whether they have done that and they have not answered my question. For USA customers, I think that this closes the chapter on Fronius support.

    Do we have any readers of this forum from outside the USA? If so, I am willing to try to contact Austria directly and take this one step further.

    Thanks for reading this.
    Mike
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Hello,

    My installer and I did one more pass of useless measurements for Fronius today. I say useless, because the usual Fronius contacts weren't available when we called them, and we got to talk to a guy that we didn't know. He asked for some system information. With that information, he was able to reply that the Fronius 5100 IG wouldn't work. No kidding!

    So in spite of the Fronius position up to now, there is a known set of conditions that are within the Fronius specifications that the unit fails with. My installer pressured Fronius to publish this information and they have refused. As noted before, they have also refused to fix the problem.

    What I do know is that the keys to determine whether the Fronius will work or not are the DC open circuit voltage, and the AC mains voltage. But I cannot give you the formula since Fronius isn't sharing.

    Fronius has now offered to buy me an autoformer to reduce my line voltage and move out of the failure window. I have refused.

    I would recommend that anyone who owns or is responsible for a Fronius IG series inverter contact Fronius with the AC line voltage and DC open circuit voltage and ask them whether the combination falls into the design flaw. If you are considering a Fronius inverter, you could do the same thing, but you might save a lot of time and energy just to specify a competitive brand.

    This is the end of the line for me and Fronius and I don't intend to post anything else. So, I'll say thanks to all of you who offered technical advice and moral support. You are a great group and I very much appreciate the time and efort that you spent on me.

    Please feel free to share my experience as you wish.

    Thanks again,
    Mike
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Fronius MPP Hunting

    sorry to hear of all of your trouble with this inverter and with fronius. thanks for sharing this info with us that others may not fall prey to the same thing.
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    Please update this thread when you install a working inverter, which sounds like it will be another manufacture
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Fronius MPP Hunting

    i'm glad to hear that there is at least a conclusion to your dilema and it's a shame that bad publicity motivated them rather than owning up to their own product short-comings or care for their customers. this gives other companies and the industry in general a bad rap when this happens.

    speaking of a bad rap, i even saw in that off the grid in tennessee thread in another forum that outback had gotten a bad rap by somebody that said they were prone to breakdown and i think that to be unfair to outback as he is giving the impression it is commonplace. for the record, all electronics is prone to breakdown and the feedback i've seen and heard is that outback has excellent service to their customers for those rare instances of breakdown.
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Hello,

    I deleted an angry and inappropriate post that I made yesterday. I apologize to those who read it.

    Fronius finally struck a deal with my installer to replace my Fronius IG 5100 with two PVPowered 2800 IX inverters and to pay for all of his expenses, including his diagnostic time. Fronius did not agree to publicize the details of the defect. However, Fronius did agree to work some sort of similar deal for another customer of my installer that has the same problem. They haven't told the customer that he even has a problem yet.

    The deal made me angry because I am pretty sure that I spent more time on the issue than any other individual and all I got was a solution that I should have had months ago. And, Fronius is off the hook for any public disclosure, so the solar community gets no benefit.

    I'll post a follow up when the inverters are installed.

    Thanks,
    Mike
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Niel,

    Thanks for your comments.

    As you can see, I deleted my post because I wrote it when I was angry and it was a rant. It made me feel a lot better to write it though.

    Situations like the Outback story happen all the time. You can't trust it just because you read it on the internet. I'm guessing that's why Fronius isn't worried about me spreading the word. Which frustrates me, because my story is reliable.

    Mike
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Fronius MPP Hunting

    understandable. yes, i understand how your problem has truth to it and the other i mentioned, well maybe one person's misguided opinion.
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Hello,

    Executive summary: No progress.

    OK, so I'm paranoid after my Fronius experience.

    Last time that I posted, I said that the final solution was a pair of PVPowered 2800 XV inverters paid for by Fronius. Well, I got a little uncomfortable with that since these inverters are no longer in production. So, I decided to test the PVP support by asking them for a copy of their inverter monitoring software. Their reply was that they no longer supported that software and if I wanted to monitor my inverter, I should buy a current model instead and they would "sell" me software for it. I would have expected that software that was included with the product, or so the manual says, would be available for at least the 10 year warranty life. I understand that they might not wish to their software to new versions of the operating system, but it still should be supported for the OS that it was designed for. And, why should I expect better support on a current inverter? PVPowered failed my support test.

    I looked around some more for an alternative solution. The problem is that I need to track an MPP of 190 volts or lower. A pair KACO 2900 inverters would do, but they introduce another problem with the code and AC wiring that make them an expensive solution.

    I also found a Power-One PVI-5000-OUTD-US single inverter with dual MPP tracking inputs that looks like the ideal solution. Its problem is that it is a "transformerless" design which requires a bunch of changes to my system to meet code. I don't mind this one bit, but my installer is not comfortable with it.

    Both KACO and Power-One seem to have good customer support.

    So, here I am being pushed into using poorly supported inverters and making a mess of my carport wall with additional disconnects, inverters and combiners. Every day, I lose about 10% of the power that I could have generated. All because Fronius refuses to fix their product.

    I'll post again when something changes.

    Thanks for listening,
    Mike
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    A pair of Xantrex GT2.5's is the best solution.

    The GT2.8 is good to 195V for the VMP, your panels are in the 230V range from your postings, so unless there is something missing, they will be the best option for your installation. Street price is in the 1700 price range ( each )

    I would NOT recommend PVpowered, especially the older units, lots of issues and performance quirks
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Solar Guppy,

    Thanks for you reply.

    I have concluded the same as you about PVPowered. I too want to use Xantrex, but it just doesn't quite make it. My panels are SunTech STP180-24/Ab-1. They are not included in the Xantrex string calculator. Using other string calculators, I see my low MPP to be at 190 volts. It gets very hot in Phoenix. I would expect to see power limiting for at least 4 months per year with the Xantrex. At this point, I don't see that as a good solution.

    Thanks for your thoughts,
    Mike
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    I think your way off on your calculations

    using the data sheet here http://www.solarshop-europe.net/solar-components/solarmodules/suntech_stp180-24-ac_m_744.html

    The vmp at standard conditions is 36.2V

    The reduction in voltage is 0.34%/C or .12V/C over standard conditions ( per panel ) , your configuration is 7 in a series string , so the vmp at 25C is 253V and for every degree C over standard its a reduction of 0.84V

    You state the VMP can get down to 190V ... that would imply a temperature of 75C over standard or the panels being 100C.

    You have reported VMP's in the 220V range, which what I would expect .. ( 39C over standard )

    With the GT's VMP good down to 195V, that would allow panel temperatures about 95C ... hard to beleive even in phoniex you would get stuff that hot, you have other issues like wire ratings that can't run in those temperature if indeed thats true. Do your self a favor and get an IR point and shoot meter if you need exact numbers, I'll hazard a guess and say, even in 110 degree days, the panels will be @75C

    The Xantrex GT2.8's are your best choice and should work fine in your configuration.
  • mradtke
    mradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: Fronius MPP Hunting

    Solar Guppy,

    Thanks for your calculations. However, there are two errors. First, you used the specification for the STP180-24/Ac, not the STP180-24/Ab-1. The difference is that the correct Vmp is 35.6, not 36.2.

    Second, you used the temperature coefficient for Voc, not Vmp. The correct value should be -0.47, not -0.34.

    Using the correct figures, I calculate the Vmpp for the system is 190 volts at a panel temperature of 75 degrees C.

    I think that the only thing left to argue is the 75 degrees C. If I use the Xantrex string calculator with the STP180S-24/Ab-1, and 110 degrees as the average high (which is appropriate for June), both the GT2.5 and GT2.8 come out as non-optimal. In comparing the STP180S-24/Ab-1, with the STP180-24/Ab-1, I find that the panel used in the Xantrex calculation is the same except for having a lower temperature coefficient. That means that the result would even be worse for my panels.

    Please correct me if I have missed something.

    Thanks,
    Mike
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius MPP Hunting

    OK, got the data sheet http://www.suntech-power.com/products/docs/STP175_24_Ab-1_E01.01%20Sept10%202008EN.pdf

    And I now do see the coefficients are different for VOC and VMP, I didn't realize they had specs for both, but the .047% is similar to other panels and makes sense

    The GT 2.8 runs mppt down to 195V, so that would allow about 47C of temperature rise above standard 25C ... so these numbers agree with your calculations

    So now the interesting questions is just how hot do the panels run above the ambient temperature? ... I bought a nice IR point and shoot Extech brand off ebay for about 50 bucks .. that is the only way to answer what you need.

    The Xantrex calculator ( or any other ) can't take into consideration your stand offs, mounts, roof surface underneath the panels or wind flow, all effect what the temperature rise could be. I also believe as the ambient temperature rise the panels temperatures do not follow in a linear fashion, I don't have a reference on this, but something along the lines that thermal energy is more efficiently radiated at higher temperatures ( from memory )

    Also, if your that far down in voltage, then it would seem you might be able to run 14 panels in a single string?. I have run here in florida a GT3.3 with a similar VOC for 3 years without issue ( 20 18V panels in a single string ). You will have to check the VOC at cold temperatures for your area.

    Before you purchase anything, I'd recommend you make actual measurements, with that data, then you can see what your options are.

    FYI, the Xantrex GT series has the widest operational range of any Grid Tie inverter, if that won't work, you may need to make other adjustments