Help! Undersize Inverter

jadijadi Registered Users Posts: 10
Solar installer came to install my system today.

26 Sharp 235 panel = 6110w.
1 SMA 6000 inverter.

When I ask, their engineer says its OK. Does anyone knows if it will toast the inverter? Or I might run into other problem down the road. How about efficiency?

They are also running 2 strings of 13 panels. Is that too much on each string?

Thanks

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,070 admin
    Re: Help! Undersize Inverter

    No, not a problem. The inverter will only output as much power as is "safe" (design and temperature limits).

    Also, it is not unusual to install an inverter that is ~86% of the solar panel rating. Unless it gets really cold and you have snow fields reflecting light onto the array--Your system will rarely (few minutes to a few tens of hours a year type thing generally) more than 86% of the solar panels rated (marketing) output.

    Yours is:
    • 6,000 / 6,110 = 0.98 of rated array power
    Not a problem/issue/or real loss of revenue at all (going to the next size inverter may cost you more than the little bit of lost revenue will ever gain back).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jcgee88jcgee88 Solar Expert Posts: 154 ✭✭
    Re: Help! Undersize Inverter
    jadi wrote: »
    Solar installer came to install my system today.

    26 Sharp 235 panel = 6110w.
    1 SMA 6000 inverter.

    When I ask, their engineer says its OK. Does anyone knows if it will toast the inverter? Or I might run into other problem down the road. How about efficiency?

    They are also running 2 strings of 13 panels. Is that too much on each string?

    I'd trust Bill's reply to your question, but also note that
    there's a bit of "it depends" in your situation.

    Do you plan to ever add any panels to the original 26?
    If so, the SB6000 might be a bit tight.

    Are your two strings homogenous, i.e., they have the
    same tilt angle, azimuth, and shading? If they are materially
    different, then you might want to consider doing two
    inverters, one for each string.

    John
  • jadijadi Registered Users Posts: 10
    Re: Help! Undersize Inverter

    John,
    Same tilt, same roof, no shading and max out on 26 panel. Will not add more.
    How are your Sharp panels. Do you like them. I had wanted the Sunpower panel but for $0.55 more per watt, I figured I can use that money towards replacing my old inefficient appliances and still have some $ left.

    Bill,
    Thank you.
  • JburgessJburgess Solar Expert Posts: 130 ✭✭✭
    Re: Help! Undersize Inverter

    My installer used a SMA 5000 with 6.3 KW of panels. (30 x 210 watt)

    I called SMA and they said that was OK.

    Been running for a year, inverter just de-rates around noon on cool sunny days.

    One of many reasons I won’t use that installer again.
  • toppertopper Solar Expert Posts: 113 ✭✭✭✭
    Re: Help! Undersize Inverter

    Funny I was thinking about this today and was going to post a similar question.
    In sunny but -35*C Saskatchewan, if I installed 7.1KW on the roof I would want as close as possible in inverter as well. Any thoughts? This would mean 2 XW4548's or 2 XW4024's(added cost for charge controllers on a 24 volt system).
    Or would one XW6048 work with 7+KW of solar?

    Sorry for hijacking your thread.
    Ken
  • jadijadi Registered Users Posts: 10
    Re: Help! Undersize Inverter

    Don't sweat it Ken, every post or reply is always educating. My installation is done today at sundown.
    Looks good so far, will know if it works by Monday when its turn on when they do a walkthru with me.
    Well..... at least I feel good to know I'll be making my own juice.;)

    jadi
  • mike95490mike95490 Solar Expert Posts: 9,033 ✭✭✭✭✭
    Re: Help! Undersize Inverter
    topper wrote: »
    Funny I was thinking about this today and was going to post a similar question.
    In sunny but -35*C Saskatchewan, if I installed 7.1KW on the roof I would want as close as possible in inverter as well. Any thoughts? This would mean 2 XW4548's or 2 XW4024's(added cost for charge controllers on a 24 volt system).
    Or would one XW6048 work with 7+KW of solar?

    Sorry for hijacking your thread.
    Ken

    The xw6048 does not have a MPPT charger, that would be a separate item.
    There are a couple 60A and an 80A MPPT charger that you could pair with the xw6048. The internal charger in the 6048, is for charging when AC line1 is present.
    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 ,

  • toppertopper Solar Expert Posts: 113 ✭✭✭✭
    Re: Help! Undersize Inverter

    Found all the answers I needed on PV watts. Just had to look objectively.
    In my case 7.1 KW solar peaks production in april @ 5.5 KW/Hr. So my thinking is one XW6048 will suffice. I will need 3 XW MPPT150-60's to handle the 3 arrays according to XW sizing tool.

    I am anxiously waiting for your first day production numbers Jadi>>>
  • jadijadi Registered Users Posts: 10
    Re: Help! Undersize Inverter
    I am anxiously waiting for your first day production numbers Jadi>>>


    Yesterday, 80F sunny all day @ 33 Kw/hr. Is that good???
    I wonder how much more I can get if it's the more efficient Sunpower panel.
    Or if there is a difference with the bigger Sunnyboy 7000. Just curious.
  • AntronXAntronX Solar Expert Posts: 462 ✭✭
    Re: Help! Undersize Inverter

    Efficiency of SB6000 is about identical to SB7000, or = 96.1% at 5200W, 310V DC nominal input. I attached .pdf files with efficiency data for both inverters. There may be short peaks when DC input will exceed 6350W maximum input power of SB6000, but capturing those will not justify price premium of SB7000. Unless you directly observe your array performing above STC rating for long periods of time, and SB6000 runs in derated power mode then you will need SB7000. Usually in warm weather your array will perform at 85 - 90% of STC rating. That would leave you with 6350 - (6110 * .9) = 851 Watts of headroom.
  • SageBrushSageBrush Registered Users Posts: 19 ✭✭
    Re: Help! Undersize Inverter
    jadi wrote: »
    Yesterday, 80F sunny all day @ 33 Kw/hr. Is that good???
    I don't understand your units. Do you mean 33 kwh production ?

    As for good or not, there are so many variable to consider. Perhaps start with your home's latitude and the panel tilt. PVwatts can get you in the ballpark for what to expect on average.
  • jadijadi Registered Users Posts: 10
    Re: Help! Undersize Inverter

    Yes, for the pass week my system produces around 33kwh to 36kwh a day. Not counting the rainy days. I got 36kwh on yesterday. Temperature high was 72F at 1pm.
    My neighbor next block stop by to check out my system. He said he will be installing soon. He had sign with a different installer a month ago, Trina poly panels for $6.25/watts. I can't wait to see the difference in performance. Originally I had sign for Suntech for $6. I later change the order to Sharp panel for 0.45 more. Why?????:confused:
  • toppertopper Solar Expert Posts: 113 ✭✭✭✭
    Re: Help! Undersize Inverter

    I hope I can be so lucky when I finally get my system up and running..
    I would be a very happy man @ 36Kwh/day in september.
    Congratulations.
  • System2System2 Posts: 6,290 admin
    Re: Help! Undersize Inverter

    Bare with me. Not sure how this works.
    I have a DIY 6 homade 3x6 poly panels; 72 cells per panel. With a SUN-250G grid tie inverter and blocking diods on pnl. Inverter starts generating about 9:00 AM; Vmin ~15vdc in to inverter; Iout .1 to 1.0 amps AC. Series (2) 12vdc old auto batteries for 24vdc system. Severial questions; as you can imagine.
    1. Inverter will sut off on over voltage protection and panels will keep inverter off with low current pnl draw. I can disconnect inverter from pnls and draw batteries down.then reconnect OK. Pnl open voltage is 41vdc. Inverter cut off voltage is 29vdc. How to suggestions?
    2.How to log & meter inverter output? I can work verywell with schematics and wiring diagram.

    THIS IS A GIVE BACK PROJECT FOR MY NEIGHBORS. THANKS
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Help! Undersize Inverter

    jay101,

    If I understand correctly, you are using homemade panels with a grid-tie inverter in an off grid application. I cannot imagine the problems you will have. Much less how to answer any of your questions.

    Sorry.
    K
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Help! Undersize Inverter

    1. A grid-tie inverter will put out zero without being tied to an active grid.
    2. It is not legal to connect a system to a grid without utility consent & involvement.
    3. There is no chance homemade panels will be permitted for grid-tie.
    4. Using a grid-tie inverter to "back-feed" an off-grid inverter or generator is tricky, problematic, and potentially dangerous.
    5. Batteries don't enter in to grid-tie except in a few cases.
    6. Like my buddy Big K, I can't imagine what sort of set-up you've really got or what you're trying to do with it.

    Could you provide a few more details? Preferably before something or someone goes up in smoke.
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