Acceptable Amount of Clipping

[JSchnee21]

Perhaps I missed the answer to this questions as I was skimming through:

How many amps is your electric panel? 200amp? 100amp? Do you have a load side tap? Aka is the output from your inverter wired to the load size of your electrical panel? Perhaps due to the 120% rule the inverter output had to be limited to 4kW so as not to exceed the number of input amps on your panel's bus bars? Though I agree this us unlikely with such a small inverter.

More than likely, the installer forgot to check the programming of the inverter (or replaced one of the boards) and forgot to make sure it was programmed correctly. Instead of actually answering your questions, they're just giving you a snow job. Usually they are correct coming from SE, but we've seen a few instances here on the board where replacement parts come pre-programmed for inverters of other (usually smaller) sizes.

[foo1bar]

Our inverter is a HD Wave SE6000H, this 4.0 limit is a setting as far as I can tell, not actually a true limitation from the hardware. I found it scrolling through the menu on the inverter itself and it seems the most likely explanation for why our 5.4 system never generated more than ~3.8. That is probably my biggest point of confusion, this limit was assigned and I don't understand why.

All panels are facing the same way at the same angle.

Is the breaker for your inverter a 20A breaker?

It's possible they essentially limited your inverter to 3.8kW because there was only room for 20A breaker.
Or maybe for some reason the wiring from the inverter to the breaker box was limited to wiring that should only be carrying 16A continuously (which is treated same as 20A as far as circuit breakers / wire sizing. )

I'd think if it was something like that they would have explained that to you as part of the design/install process.
(Or possibly they did try to explain it, but it didn't get explained in a way that you understood it.)

If all the panels are facing the same way at the same angle and there isn't a shadow (ex. power pole or telephone wire) that's hitting your system at that peak production time, then it must be clipping you are seeing, based on the first picture you attached with the output graph. I really doubt a shadow could cause that flat of a top on your production curves - but theoretically I think it'd be possible (just so unlikely it's basically impossible)

[foo1bar]

Without bustin' on the OP too much, I'm wondering why a trip to the inverter and a read/picture of the nameplate on the inverter can't be done and maybe end some speculation or provide more info as to what's going on.

They already posted that it's a SE6000H.

2.) If the inverter is a 6000H, why was it oversized compared to the 5.44 STC kW of panels installed ?

I don't think that would be considered "oversized". "oversized" has a connotation that it's not the natural choice.
With 5.4kW of panels it lands in between the SE6000H and SE5000H. Going with the SE6000H is a reasonable/natural choice - potentially allows for expansion. And guarantees you don't have clipping.
Going down to SE5000H would also be reasonable (might save a few dollars on the inverter and might be able to go with slightly smaller AC wiring.)

I think a less confrontational phrasing when asking the installer is "Why was the inverter SE6000H chosen? I see it's rated for more watts than the total watts of panels installed."
(possibly the answer will be "so there's no clipping" - which leads to "But I see that the power limit on the inverter is set at 4-point-zero killowatts, so it's clipping anyhow?")


If the OP has been communicating with the installer by phone, I'd try to do it by email instead. Show the pictures to them in the email.
Use the pictures as an excuse to get an email address if you don't have one already.
Email gives you a chance to be more deliberate in your response. (If you're already unhappy with them, which it sounds like the OP is, you can wait an hour after your first draft and rewrite it more politely. Or at least so that you don't sound like a complete raging <expletive> if it winds up in court)
And if it does wind up going to court or mediation, having the record is good - especially when you don't look like a jerk but they do. If it's really contentious the OP may even want to do follow up emails after phone conversations. ex. "Hi Jim. This is just a follow up email to our conversation today at 2PM. Per our conversation I am expecting your crew to arrive on Friday in the morning and I will be there to provide access...."

Even if it's not that contentious, I think email has a good chance of having slightly more visibility and therefore more likely to get it resolved sooner and not forgotten about. it may go to a higher level supervisor or the owner. And it can be easier for someone to pass along - ex. forwarding it to someone else in the company. (Of course there's the risk that it can potentially be a blackhole too - never responded to by anyone)

[jflorey2]

Given this, can anyone say whether this is to be expected?

To figure out roughly how much is being lost:

1) Print a typical day's power plot on a big piece of paper.
2) Draw (freehand) what the top of the curve would look like. If the panels are all in one direction, it's just the top of a sine wave.
3) Estimate the area under the curve. You can do this with simple calculus (eek) or do it piecewise with a spreadsheet. That's power loss in kilowatt-hours.

Figure out how much that will save you if you had the extra power. Then figure out how much it might cost you to upgrade (if you can't get the installer to do it for free, that is.) That will tell you whether it is worth it.