[RE-wrenches] String fuse blown
Ray Walters
ray at solarray.com
Mon May 12 09:41:11 PDT 2025
Is inverter 2 on top? The top inverter in an Outback dual stack always
runs hotter, because the heat from the bottom inverter is adding to its
own heat. I used to see that consistently cause board failures on the
top inverter more often, if the whole system was running close to capacity.
Ray Walters
On 5/12/2025 7:56 AM, Amos Post via RE-wrenches wrote:
> UPDATE:
>
> So far so good and since replacing the fuse holder, fuse #3 has not
> blown again.
>
> ANOTHER ISSUE:
>
> *Inverter 2 runs hotter than inverter 1.* Reminder this is grid-tied
> system with 2-GVFX3648’s in series for 120/240V. The fan on inverter
> #2 had malfunctioned, but I was able to replace it and get that going
> again. Even with the replaced fan, inverter #2 is still running
> noticeably hotter. My understanding is that both inverters in this
> system are essentially “Masters”, since this is grid-tied. Shouldn’t
> the load/generation be split between the two and hence they run
> equally as hot? I did check the stacking and they were both set to
> “Master” which is I think what they recommended for grid-tie. I tried
> switching the ports on the Hub that they are plugged into to see if
> that would change anything, but no change. I did also noticed while I
> was there last week that while both inverters had the solid yellow “AC
> IN” light on, inverter #2’s green “Inverter” light was always on,
> while inverter #1’s green “Inverter” seemed to come and go…
>
> Any ideas?
>
> Thanks as always,
> Amos
>
>
>
>
>
>
>
> Amos Post
> Integrity Energy
> W 802.763.7023
> C 802.291.2188
> ienergyVT.com <http://www.ienergyvt.com>
> Facebook <https://www.facebook.com/integrityenergyllp?ref=hl>
>
>> On Apr 15, 2025, at 8:40 AM, Amos Post <integrityenergy101 at gmail.com>
>> wrote:
>>
>> Hi all,
>>
>> I decided to start with the simple stuff. While I don’t have a
>> string curve tester (I should have one), yesterday I tested strings
>> 1,2,3 individually under load. String 3 is the one that’s been
>> blowing the fuse. I did not test strings 4-6 which are on a separate
>> charge controller and combiner. Here are the results:
>>
>> String 1- 7.1A at 76V
>> String 2- 7.77Aat 79V
>> String 3-7.13A at 78.3V
>>
>> I did notice that the second charge controller with strings 4-6 was
>> running about 100watts more (1800w vs 1700w). The conditions were
>> clear blue skies. I replaced the fuse holder and fuse. If it blows
>> again I’ll try switching strings to see if it follows…
>>
>> Thanks for your feedback and I’ll keep ya’ll posted.
>>
>> Amos
>>
>>
>> <IE LOGO 150x78.jpg>
>>
>> Amos Post
>> Integrity Energy
>> W 802.763.7023
>> C 802.291.2188
>> ienergyVT.com <http://www.ienergyvt.com/>
>> Facebook <https://www.facebook.com/integrityenergyllp?ref=hl>
>>
>>> On Apr 11, 2025, at 4:07 PM, Jerry Shafer via RE-wrenches
>>> <re-wrenches at lists.re-wrenches.org> wrote:
>>>
>>> Wrenches, Amos, blowing of a 15 amp fuse is not a ghost in the
>>> machine, it is an actual issue no way around it, shorted modules,
>>> shorted diodes, in most cases it's a home run, way back when USE-2
>>> white wure was failing and would crack and break off mostly this
>>> would result in a GFI trip. The fuse is blowing because of over
>>> current and a single string of your vintage will max out at far less
>>> than 10 amps but the other two strings will back feed this fuse with
>>> close to 20 then pop.
>>> Sharp had module failures resulting in cell shorts, look very close
>>> there. I have inspected arrays with extreme exposure differences,
>>> this will effect performance but should not pop a fuse. Do you have
>>> a module string curve tester, this very well may show an issue of
>>> the string but eyes on the array is required to located the cause.
>>> I have seen nails through wires, conduit, racking in contact with
>>> the back of the module but this will trip the GFI breaker not the
>>> string fuse.
>>> Fun times.
>>>
>>>
>>> On Fri, Apr 11, 2025, 12:49 PM david quattro via RE-wrenches
>>> <re-wrenches at lists.re-wrenches.org> wrote:
>>>
>>> One time I had similar, but different problem: 1 Amp ground
>>> fault fuse consistently blowing, sometimes after 1 day sometimes
>>> after weeks/months. I tried everything - replaced home runs,
>>> checked VOC, VMP, swapped DC input into a different inverter,
>>> etc. it kept coming back to this one string. I checked every
>>> module VOC, ISC, every connection, no pinched wires, no
>>> discernible problem, but fuse blowing.
>>> Luckily it was a medium size commercial job (on a fire
>>> station) so I was able to scatter all the modules of this
>>> suspect string all over the roof, and carefully track where I
>>> had put them. That’s when the problem went away and never came
>>> back..😂
>>> Best I could figure was a slight manufacturing error that had
>>> a compounding/cumulative effect. So once I got those consecutive
>>> serial numbers away from each other no more problem. Either that
>>> or the fire chief was fucking with me and he was burning out the
>>> fuses, which I doubt
>>>
>>>
>>>
>>> On Fri, Apr 11, 2025 at 8:05 AM Mac Lewis via RE-wrenches
>>> <re-wrenches at lists.re-wrenches.org> wrote:
>>>
>>> Hello Amos,
>>>
>>> Have you checked for voltage imbalance for each string? If
>>> you have a bad diode, that string may run low on voltage and
>>> be trying to send current toward the weak string (this is
>>> the reason you have these breakers). I'd run each string
>>> independently and see what Vmp is. If you are missing some
>>> voltage that may be a clue. You can also independently
>>> clamp each string during operation.
>>>
>>> I like IR cameras for this type of thing. It may just be a
>>> bad connection, heat build up, fuse holder issue.
>>>
>>> Let us know what you find out
>>>
>>> On Fri, Apr 11, 2025 at 8:07 AM Amos Post via RE-wrenches
>>> <re-wrenches at lists.re-wrenches.org> wrote:
>>>
>>> Hi Wrenches,
>>>
>>> I have a bit of a puzzler that I’m trying to get sorted
>>> out. I’ve been servicing a Grid-Tied Battery Backup
>>> system that’s about 17-18 years old. The system
>>> comprises of 2-GVFX3648s in series, with 2-MX60(at least
>>> I think they are 60s) CC’s. Each CC has 3 strings of 3
>>> tied to it, and each string has a 15A in-line 600V fuse.
>>> The modules are I believe are like 230/240Watt 60 cell
>>> modules (sorry I don’t have pictures/specifics). We
>>> replaced the flooded batteries with AGMs about a year
>>> and a half ago.
>>>
>>> The situation is one of the 15A string fuses keeps
>>> blowing. It’s now happened 3 times and its the same
>>> fuse every time. First we just replaced the fuse and
>>> under the surge/lightning assumption. Fuse blew again.
>>> Then I thought I found the culprit. The #6 PV output
>>> from the combiner to the PV input breaker for the CC was
>>> a bit darkened and very warm to the touch when I
>>> replaced the fuse the first time. So I though maybe it
>>> was a loose connection on that lug and that caused
>>> everything to heat up and eventually blow the fuse. I
>>> cut and stripped the wire back and cleaned the lug and
>>> re-seated the wire in the lug. Fuse blew again within a
>>> few months time. I then checked the Junction box on the
>>> roof where the USE-2 wire connects to THHN, and did a
>>> visual inspection of all the wiring on the roof. All of
>>> the Jbox connections and everything on the roof “looked”
>>> ok. I have also check all of the connections inside the
>>> Outback DC load center, and they look ok. Fuse replaced
>>> 3rd time and then it blew again.
>>>
>>> Before I take all of the panels off the rack, check
>>> panels, re-check string wiring on the roof, is there
>>> anything else I should be checking? Seems like that
>>> warm wire in the Combiner box is telling me something
>>> but I can’t figure out what...I believe this is a new
>>> problem in the last 2-3 years but we are not 100% sure
>>> when the problem first came up…
>>>
>>> As always, thanks for your help/ suggestions!
>>> Amos
>>>
>>>
>>> <IE LOGO 150x78.jpg>
>>>
>>> Amos Post
>>> Integrity Energy
>>> W 802.763.7023
>>> C 802.291.2188
>>> ienergyVT.com <http://www.ienergyvt.com/>
>>> Facebook
>>> <https://www.facebook.com/integrityenergyllp?ref=hl>
>>>
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>>>
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