I kinda remember running into something like this a few years ago.. Turned out
it was the Flexnet DC throwing curve balls to the system.. Flexnet does not
play nice with LiFePo4.
db
________________________________
From: RE-wrenches <[email protected]> on behalf of Amos
Post via RE-wrenches <[email protected]>
Sent: Thursday, May 15, 2025 10:24 AM
To: RE-wrenches <[email protected]>
Cc: Amos Post <[email protected]>
Subject: Re: [RE-wrenches] String fuse blown
Hey all,
To close the loop on this, I doesn’t look like its a “Power Save” setting as
those are available on Grid-Tied FX’s. I went yesterday and confirmed that
just Inverter #2 is pushing power when grid-tied ( 21A at 120V is what I
tested at the time), however both start inverting (indicated by green LED) when
grid-goes down. But it seems to be functioning like the Power Save modes and
shutting down Inverter #1 when grid-tied.
My best guess is since the array is only 4.2KW and a shallow roof and never
really hitting that 4.2KW peak (2.0-3.0KW typical on a sunny day), it’s only
running the power through 1 of the inverters because it only needs to run 1.
There are no errors, or warnings on Inverter 1, and what’s weird is even when I
switch the inverter ports on the Hub (swap 1 and 2), Inverter 2 is still the
only one that’s inverting typically. The exception was when I was testing I
shut off grid power for a few minutes to test the backup function, during which
the batteries did an absorb charge. When I reconnected the grid the inverters
started to sell some of that battery power(for a minute), along with the PV,
down to the sell voltage. Then once the voltage leveled out, inverter #1 went
to sleep again.
If this was Myth Busters I would say “Plausible” because I’m not really sure… :)
Thanks for your brains!
Amos
[cid:BB04EA26-2543-45F1-9D19-B078F743C9C6]
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 May 12, 2025, at 12:53 PM, Amos Post
<[email protected]<mailto:[email protected]>> wrote:
Oh I forgot to mention the inverters are side x side on 2 individual Panels….
<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 May 12, 2025, at 12:48 PM, jay via RE-wrenches
<[email protected]<mailto:[email protected]>>
wrote:
good point.
For GT OB systems I have removed the side screens for better air flow and I’ve
also taken the covers off and used external fans to cool them.
They just were not designed to run anywhere near rated capacity for long
periods of time, they don’t have enough air cooling.
On May 12, 2025, at 10:41 AM, Ray Walters via RE-wrenches
<[email protected]<mailto:[email protected]>>
wrote:
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
<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 15, 2025, at 8:40 AM, Amos Post
<[email protected]<mailto:[email protected]>> 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
<[email protected]<mailto:[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]<mailto:[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]<mailto:[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]<mailto:[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<https://www.facebook.com/integrityenergyllp?ref=hl>
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