That sounds like a generator problem. I've seen many gen sets put out a
horrible waveform under load, when battery charging. The waveform, (if
you have an O-scope) usually has a spike on the front of the wave, and
then the wave flattens significantly after. The peak should be 169 v on
a 120 vac RMS sinewave. I've seen it as low as 135v on crappy
generators that are over loaded. THD is a great thing to check, but
also check your peak voltage, if you have a quick capture feature on
your meter.
It also could be related to altitude, gen sets can perform badly when
they can't get enough air. You didn't mention gen set model, or
whether the frequency was a solid 60 hz. I've seen bad things happen
when the frequency got out of spec too. I'm guessing a bad voltage
regulator on the gen set.
Ray Walters
Remote Solar
On 4/25/2024 11:24 AM, Kevin Pegg via RE-wrenches wrote:
Hi Wrenches,
Curious if anyone else has seen this issue.
New XW Pro off-grid system installed Dec 2023. Pretty standard config
for us, XW Pro, 5 kW PV, 50 kWh UnigyII battery, 8 kW high quality
diesel generator. This system ran fine all winter long – powering
customer’s big RV they were living in while the house is built, Shop,
computer controlled outdoor wood boiler, domestic loads + 3 person
construction crew. Gen ran daily on auto start as we don’t get much
sun Dec – Feb. No issues reported.
Couple weeks back I did a new system check up. All performing well,
happy client. Part of that service I upgraded the XW firmware from
1.09 to 2.04, and insight from 1.16 to 1.18. Gave the system a quick
check, ran gen. Lots of sun now, batteries full so didn’t do a long
generator test. Yes I set the region codes for off-grid.
A week later, while I was out of town and it was not so sunny so gen
running, client and their electrician called me in a panic. Two smoke
detectors had literally melted, as well as several dimmable LED
fixtures all failed. Electrician replaced the burned up devices, only
to have the same thing repeat a few days later. Talking with them it
was only when the generator was running there were issues. Told them
to lock out gen and I will get there when I can.
Once back I attended site, fired up gen, and could hear the inverter
sounding terrible during gen charging. Lights flickering bad, and I
personally verified the smoke detectors beeping and getting warm and
the house smelled like burned plastic. I hooked up my power quality
analyser and could see the THD gradually building to over 36%. Gen
voltage was at 125/250V a bit high, so adjusted that, but no change.
By reducing the charge rate on the XW Pro to 50% was able to get the
THD down around 12% and less light flicker. But it’s still too high.
Image attached shows THD with gen on original programing, then at
reduced charge rate.
Have now gone from a happy client to a pissed off client threatening
legal action for endangering their lives & a bill from the
electrician. Ugh. Having a hard time explaining this to the client why
a system previously working fine went sideways so badly. Old guy
blames the “darned computer stuff” and he’s not wrong with that opinion.
At another site, similar config but larger system with dual XW’s that
I upgraded to 2.04 firmware remotely few days ago and now the two
inverters are literally fighting each other under generator charge –
one load building to +6 kW and one (minus)6 kW.
Sure makes me reluctant to upgrade firmware on systems that are
working fine.
Any suggestions?
Kevin
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