On Apr 11, 2025, at 4:07 PM, Jerry Shafer via RE-wrenches
<[email protected]> 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
<[email protected]> 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
<[email protected]> 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
<[email protected]> 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
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