Solar Edge major unresolved problem

[DanS26]

The installer did give me an alternative proposal for a #1 aluminum wire for $4400. The proposal for the #4 copper is $4100. Cost aside, is the aluminum preferable?

Don't know what's all in that proposal.......but you need to get competitive quotes.

[bcroe]

Check your inverter specs.....most inverters will not accept large gauge alum. A conversion to copper will have to take place somewhere.

Here the inverter AC is wired to a disconnect box, that to a circuit breaker,
the breaker plugged into a dedicated distribution box. So the box is what
must interface to the long run. Here a 200A 20 circuit box was a couple
hundred $, I used one which easily connects even to my 4/0 aluminum.

understand gauges
6
5
4
3
2
1
0 or 1/0
00 or 2/0
000 or 3/0
0000 or 4/0

6 to 1 is 5 steps larger, which gave the improvement I wanted. BUT
that is for similar metal, going from copper to aluminum you must go
2 more steps to get the same performance.

15KW, I went from 4 copper to 0000 or 4/0 aluminum. The 300 ft roll
of aluminum triplex was (in 2019) $650 delivered. I estimated the
equivalent performance 00 or 2/0 copper would be $2600. No the
aluminum is not better, but it is WAY cheaper. These items were about
my only expense for a run of about 260 ft.

I do not know how the installer arithmetic works, but it is way different
from mine. Given your shorter run and and the overall smaller wire
(and your voltage issues to date), I think the installer is shorting you
on the wire, wasting energy, and might not cure your trip problem.

250 ft of the wire I mentioned is $700 delivered today, cannot believe
copper of similar performance could come close. Bruce Roe

[Treepmeyer]

The installer did give me an alternative proposal for a #1 aluminum wire for $4400. The proposal for the #4 copper is $4100. Cost aside, is the aluminum preferable?

[DanS26]

Check your inverter specs.....most inverters will not accept large gauge alum. A conversion to copper will have to take place somewhere.

[bcroe]

My guess, your 6 ga is running 40A, dropping some 8V in the
loop, that gets added to the line voltage. Power loss of over 3%,
much like mine was. If going to this trouble, I would not go to
4 ga, I would go to 2 ga, recovering most of that loss and making
the most impact on the V trip problem. 1/0 ga aluminum will do
as well and cost less, direct burial would be the simplest. Look
up 1/0-1/0-2 Triplex Aluminum URD Direct Burial Cable. Here
the original cable was not disturbed, no service lost time.

Certainly address if the line voltage can be lowered. Or find
someone who can bump up the inverter V monitor settings. I
was able to do that on Fronius.

A clumsy solution is use a dual lead auto transformer to knock
off like 5 volts on each line to the inverter. But it would need to
handle like 500W, and would draw idle current 24/7.
good luck, Bruce Roe

[Treepmeyer]

My power company is Indiana/Michigan Power. I live in Michigan, 15 miles north of the Indiana border.

Last December the power company put a data logger on my meter for a week. Average was a little over 124v, standard deviation about 1.5v, absolute peak 127v. The inverter routinely (as in multiple times per sunny day) records voltages in excess of 260v. Solar Edge says that they expect a 3% voltage rise over a run like mine. Two standard deviations on the logged data should be about 126.5 and adding 3% gets one to 260.6. So under these conditions I should expect to see some shutdowns, but nothing like I experience with the inverter shutdown so frequently, and often for hours, that production is off 50%. I can't see it because the inverter shuts down, but it looks like voltage routinely heads north of 260v on any reasonably sunny day.

Are there perhaps three problems here? One, that given the slightly high grid voltage and the inverter threshold set at 260v (if, indeed, it is), there is not enough headroom for the expected voltage creep. Second, voltage at the inverter routinely exceeds the expected 3% increase. And third, the inverter seems to vary considerably the voltage at which it shuts down, and for how long it stays down.

[nerdralph]

Mike 134 - Your post prompted me to wonder why the power company would set the local regulator at anything other than 120/240 which I believe is the service they are obligated to provide. They are turning it down to 123/246 and I expect that will help, but 120/240 might solve the problem.

CSA C22.3 No.9 defines OV1 as > 110% for 2 seconds, or 264V for a nominal 240V split phase service. I imagine your local utility follows a similar standard. I find most utilities distribution zones are designed to be a few percent hot, to help compensate for voltage drops from high loads. On a cloudy day when my PV system is putting out little power, L-L voltage at my panel is usually between 245 and 249 Volts. When the sun is out, that goes up by about 2 V, and at the inverter it goes up by a few volts more. My inverter monitoring has never recorded more than 255 Volts.

[DanS26]

My local power company (ComED) in Illinois shoots for 120/240 however anything +/- 10% of those numbers is considered acceptable.

As to your voltage depends on where you're at in the line. They need to be sure the furthest customer gets 240 so if your close to the transformer you'll see more.

Mike, that's a very good point. Here in Indiana the voltage supplied to customers is regulated by the Public Service Commission. If your voltage is outside of required parameters, then you have a right to complain. It's been my experience the POCO's are very responsive to complaints to the PSC, well at least here in Indiana they are.

[Mike 134]

My local power company (ComED) in Illinois shoots for 120/240 however anything +/- 10% of those numbers is considered acceptable.

As to your voltage depends on where you're at in the line. They need to be sure the furthest customer gets 240 so if your close to the transformer you'll see more.

[Treepmeyer]

Nerdralph - Actually, I did replace the breaker, although I didn't mention it here. The original installation used a 60 amp breaker and at the recommendation of the head electrician at the new installer, Michigan Solar Solutions, I replaced it with a 70amp breaker. Didn't help, unfortunately.

The head electrician thinks the problem is with the power company's connections coming into my house and wants them re-crimped. Solar Edge tech support agrees. The power company has inspected these connections with thermal imaging and found nothing unusual. As a consequence they don't want to send a bucket truck and crew to check the connections. Impass.

I asked Solar Edge tech support about the trip voltage threshold for shutdown and they actually refused to answer my questions! They just referred me to the inverter data sheet. As far as I can see from that, the inverter operating range tops out at 264v, but I can see that the inverter actually shuts down when voltage is anywhere between 258v and 262v. Tech support will only say that "the parameters are set correctly" or something similar. I have to say that Solar Edge has been unhelpful and very frustrating to work with.

Mike 134 - Your post prompted me to wonder why the power company would set the local regulator at anything other than 120/240 which I believe is the service they are obligated to provide. They are turning it down to 123/246 and I expect that will help, but 120/240 might solve the problem.

[nerdralph]

Another consideration is just upgrading the breaker. They are thermo-magnetic devices, and rely on the internal resistance to heat up the breaker for the slow trip function. Electricians tend to size breakers assuming a 60C rating for wire and terminations, even though most circuits are good for 90C. A higher-amperage breaker will have a lower internal resistance, and therefore a lower voltage drop. Here in the GWN, the CEC says 90C rated #6 is good for 75 Amps with no more than 3 conductors in a raceway or cable.

[bcroe]

As Mike 134 says, any permanent increase in losses is probably at the wire
connection points, not in the run of the wire.

If you do the arithmetic, you can get a pretty good estimate of your wire power
and voltage losses. Temperature is a secondary, temporary effect. Arithmetic
here was 4 gauge wire running through 2 buildings and a 200' trench, the 600'
loop at .00025 ohm per foot had a resistance of .150 ohm. My 60 A thru .15
ohm gave 9VAC drop, which was boosted on top of the line voltage. That got
my energy to the meter for credit. But there is some more wire out to the pole
transformer, so the total boost was a bit more than 9V, to trip V monitors.

My 60A at 9V cost me 540W, maybe 800KWh a year. And V trips. Bruce Roe

[Mike 134]

Just an FYI I checked my Solar Edge spec sheets and it's design is 120/240 volts with an operating range of 216V-260V. With your utility delivering 250V you lose 10V of margin from the get-go. Them changing the transformer taps to lower your incoming voltage can only help.
As to your question about damage to the #6, the cable itself is fine it's the connections that can loosen over time with the load cycling.

[Treepmeyer]

Bruce - Thanks for relating your experience. If I understand correctly, what your experience shows is that the initial wire loop was inefficient - meaning higher resistance? The higher resistance lead to greater thermal loss, and probably further increases in resistance - all leading to increased voltage over the line tripping the monitor off. Do I have that right? In my case, the 200ft. #6 line may be spec but may also be causing a slight increase in line resistance that increases in a daily cycle as inverter current builds (and falls). If the grid voltage is a little too high and the trip point a little too low the net result is frequent inverter shutdown, especially during sunny afternoons. Sound plausible?

One thing further: the problem seems to have gotten worse over the 4-year life of the system Is that likely due to damage to the #6 line from thermal cycling?

Tom Reepmeyer

[bcroe]

Triplex1.JPG I went through that problem 8 years ago. My existing wire loop
600 ft long was only running at 3/4 capacity. BUT the losses
exceeded 3%, 540W in this case. That loss did not make me
happy. I was building 9V in the loop at 60A, at the end of every
sunny day the wire was warm to the touch. That constant thermal
cycling would tend to work connections loose, I had re tighten
some for a couple years befor they stabilized.

One day the PoCo had a brief outage to do some work, and came
back with my 120/240V high line, higher than ever at 127/254V.
BESIDES the 9V bucked in my wires, the PoCo wires added a
bit more, and my inverter 264V voltage monitors tripped out. I
could not run.

My point, just because the wire is not overheating, does not mean
an acceptable design. EFFICIENCY and operating margain matter.
Eventually I buried a 270 ft run of direct burial aluminum TRIPLEX
to bring my losses to 23% of what they had been, read about that
in one of my threads. The wire only cost $650 delivered, but bigger
termination equipment was needed to deal with the aluminum. The
convenient 3 wire triplex had a smaller neutral, fine since it did not
carry inverter current and did not need over sizing.

In the shorter term I did manage to get the PoCo to lower their
voltage, but I was not about to lose forever energy while waiting
to see if/when that would happen. The inverter voltage monitors
were nominally set for 240 operation, but the same inverter could
operate on a 277VAC line if so programmed. The voltage monitors
do not set the voltage, the power company does. So raising the
line-to-line and line-to-neutral monitor trip points was a short term fix.
Bruce Roe