What could be happening

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Gazz
Gazz Solar Expert Posts: 38 ✭
in Solar Beginners Corner #1
Attachment not found.

Can anybody tell me what might have happened, had a clean sky all day and when I got home I saw this, big drop in output at 2.00pm. Have had the system for 5 weeks and this is my first full day of sun.

Gary
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: What could be happening

    Let's see; the batteries could have reached full charge and the controller stopped sending them massive amounts of current. Since the meters only read Watt production that is actually used, that's probably it.

    Never judge your system by one day's data, much less one moment in that day. Keep watching and see what kind of results you get over a month or so.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #3
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    Re: What could be happening

    Garry,

    This is a Grid Tied system?

    If so, and there where no shadow issues--I would guess there is a problem in the solar array wiring and/or a bad panel connection/or even a bad--open--panel. If your GT Inverter can tell you the input voltage / current (and output voltage/frequency)--those numbers may tell you more too.

    No faults indicated?

    If you have an accurate digital volt meter... Measure the voltage at your home and make sure that it does not exceed the ratings (high or low) for your power lines. Also, if you have a meter to measure the frequency--might double check that too (if this was a very hot day and the grid was over loaded with Air Conditioners, the utilities can drop the frequency).

    The second set of issues (voltage/frequency) seem less likely--It appears the GT inverter is still outputting some power--Voltage/Frequency faults would cut the power to zero for at least 5 minutes (and would not turn on until the fault is corrected/self corrects).

    This would certainly worth calling the installer about.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: What could be happening

    Bill;

    Ever notice how you always assume a system is grid-tie and I always assume it's off-grid? :D
    I guess we're kind of "polarized" in our thinking! :p

    (Okay, there's a joke in there somewhere. But we may never find it with an archeological expedition!)

    To the OP: the remark I made about not judging on one day's data still holds. If your system consistently displays this afternoon drop-off and is grid-tie, my first suspect would be unexpected shadows.
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  • Gazz
    Gazz Solar Expert Posts: 38 ✭
    #5
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    Re: What could be happening? please

    Attachment not found.

    Sorry should have given more info, the system is grid-tie.

    I have monitored it for the past five weeks, although I have not had a full sunny day (I'm in the UK )

    The picture below is from a few weeks ago although not a perfect sunny day, so you can see it can produce a normal curve.

    I will add that although late in the day about 4.00pm I get a bit of shadow on one panel I have never noticed any power output drop and the problem I have today was at about 2.00pm when there is no shadow.

    Attachment not found.

    I have 12 Sanyo 240HIT panels and a Sunnyboy SB3000 in one string. When I came home about 5.00pm the Voltage was 380V, I'm sure it is normally about 420V buts its in my loft so not easy to get too and I haven't recorded it.

    Any more thoughts would be appreciated.

    Gary
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #6
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    Re: What could be happening? please

    Any way to tell if the sunny boy is getting too hot, and shutting down? Where is it located? Are you able to look closely at each panel, and look for hot spots or burn marks from one going bad ?
    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 ,

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  • Gazz
    Gazz Solar Expert Posts: 38 ✭
    #7
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    Re: What could be happening? please
    mike90045 wrote: »
    Any way to tell if the sunny boy is getting too hot, and shutting down? Where is it located? Are you able to look closely at each panel, and look for hot spots or burn marks from one going bad ?

    The Sunnyboy is in the loft space (Attic) it was only 70F and when I went in the loft it did not seem to hot. I can't look closely at the panels as they are on the roof. I will be contacting the installer, but though it would be nice to have some ideas of what it could be.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #8
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    Re: What could be happening? please
    Gazz wrote: »
    I have 12 Sanyo 240HIT panels and a Sunnyboy SB3000 in one string. When I came home about 5.00pm the Voltage was 380V, I'm sure it is normally about 420V buts its in my loft so not easy to get too and I haven't recorded it.

    12 of those panels should give you a voltage of 426V under ST conditions. You should only see a few volt drop due to heat in the UK summer - definitely nothing to warrant a 40V drop. The Vmp of each panel is 35V, so you may have a lose connection in the last panel? Although looking at the graph it looks as though you've lost more than just 1 panel.
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  • Gazz
    Gazz Solar Expert Posts: 38 ✭
    #9
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    Re: What could be happening? please
    stephendv wrote: »
    12 of those panels should give you a voltage of 426V under ST conditions. You should only see a few volt drop due to heat in the UK summer - definitely nothing to warrant a 40V drop. The Vmp of each panel is 35V, so you may have a lose connection in the last panel? Although looking at the graph it looks as though you've lost more than just 1 panel.

    Thanks,

    The installer wants me to monitor it for a few days, problem is its not very sunny for the rest of the week, problem might only occur when its hot weather as it was yesterday.

    I'll keep an eye on the voltage

    Thanks again.
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  • Gazz
    Gazz Solar Expert Posts: 38 ✭
    #10
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    Re: What could be happening? please
    stephendv wrote: »
    12 of those panels should give you a voltage of 426V under ST conditions. You should only see a few volt drop due to heat in the UK summer - definitely nothing to warrant a 40V drop. The Vmp of each panel is 35V, so you may have a lose connection in the last panel? Although looking at the graph it looks as though you've lost more than just 1 panel.

    Have you any idea how you would diagnose a possible fault like this? especially if it is heat related and intermittent.

    Gary
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #11
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    Re: What could be happening

    this is all speculation here. the voltage loss may point to a pv failing, but the bypass diodes would allow the power from the rest of the string to pass. this would be an imbalance though to other paralleled strings, but to reduce that much in power overall is questionable. if steady outputs continue as you have observed before with less than clear skies it would clearly be a thermal failure issue and i am suspecting the inverter. it is the internal temperature the inverter reaches that may be enough to allow a faulty area to foldback on its power. you can't overlook wires and connections either as there may be a fault there too.
    obviously, if the output never returns even to previously cloudy levels then the problem is no longer an intermittent one and the heat just put it over the edge.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #12
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    Re: What could be happening

    I'd be very suspect of the attic heat. Attics heat up very quickly, even on cold days
    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 ,

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