Question about SolarEdge inverter sizing and clipping

[J.P.M.]

Attempt #2 (copied from notepad to try to get whole posting in here)

My zip code is 60564

Here is what I found on the design doc:
AZIMUTH 180
TILT ANGLE 25

My SolarEdge 7600HD inverter does seem hard limited to 7600 AC output power. I was under the impression it could generate more, but it seems it can just take in more DC input and is limited to 7600 W AC output hard limit.

Here is the information for the two days where I saw a good amount of clipping (in my opinion):
5/22 59.44 kWh System production and 10:45am CT to 2:30pm CT clipped at 7600 W during that 3 hour 45 minute duration
5/23 46.16 kWh System production and 10:45am CT to 2:30pm CT clipped at 7600 W during that 3 hour 45 minute duration (Note: system was down during clipped time frame on 5/23 for 45 minutes due to some export/import monitoring configuration adjustments to make those functions work)

I do not think it is a shade issue for the clipping. I do have a chimney and it shades the panel on the left and right of it slightly during the day this time of year only, but not that much.

I had tried to get a 10000HD inverter installed but the installer convinced me that the 7600HD would be able to handle my system and that my clipping loss would be minimal. I'm not so sure that will be the case. I feel like June/July/August will have some nice sunny days where I lose almost 4 hours of 9.855 kW - 7.600 kW = 2.255 kW theoretically each hour (though I realize there will be loses in inverter conversion and the panels won't necessarily generate that full amount...though, they are 27 total LG 365 W panels all facing south, so I'm not sure...)

Any suggestions or comments on the above would be appreciated.

I took your info and did a PVWatts run with a 1:1 DC to AC ratio (meaning a 10 kW inverter) and took the hourly output option. Then, I sort of bastardized the intent of the model and compared the hourly output with what you provided.

1.) The max. modeled hourly output is ~ 9.27 kW.
2.) using A 1:1 DC to AC ratio, I subtracted 7.6 kW from all hourly outputs that exceeded 7.6 kW and summed the results. That result is 83.1 kWh for the year.
3.) The number of hours per year that the model thinks your system's output will exceed 7.6 kW IF you have a 10 kW inverter is 183.
4.) PVWatts modeled your shade free annual output with a 10 kW inverter at ~ 14,019 kWh/yr.
5.) PVWatts modeled your shade free annual output with a 9.855/7.6 = 1.30 DC to AC ratio (a 7.6 kW inverter) as ~ 13,957 kWh/yr. There is some rounding/quirks in the model making the 10kW inverter annual output - 7.6 kW inverter output different than I calc'd the differences. Life is not perfect and neither are models.

So, misusing the model from its tended purpose, but not terribly so, and doing so for the purpose of maybe getting some feel for the order of magnitude of what the losses from a smaller inverter might be vs. a larger inverter over a "typical" (and note as opposed to, and NOT, an "average") year, you'll lose maybe (83/14,000) kWh/yr. ~ 0.006 of the annual output according to a reasonably conservative model.

See the PVWatts model and the help/info screens therein for particulars of inputs and also see NREL for an explanation of a "Typical Meteorological Year", what it is, how it's used, and why it is NOT an "average" of weather conditions.

[Jeff72]

I have 11.2kw of pv panels in southern British Columbia and a 7.6 ev inverter.
I expected to get clipping when I installed it. On a sunny day i draw a straight line at 7.6 kw from 10am till 4pm.
I installed the 7.6 strictly for the EV portion.
I am waiting for the 11.4 kw EV inverter to come out and add a third string to my existing system.
I have to say I am happy with the 70 plus KWhours i am producing on sunny days

I am not sure I understand. You have 11.2 kW of panels but you also went with 7.6 kW inverter. I would think you would want a 10 kW inverter also to make use of those panels fully?

I still don't get why they undersize the inverter for a panel array that can theoretically do a bit higher like my 9.855 kW and your 11.2 kW.

[Jeff72]

You can look at your graphs on the monitoring site and see that the production ramps up and down on a parabolic curve so you would NOT EVER have a solid block of clipping.
you PV modules are NOT going to produce the full DC STC rating especially in summer.
your shadows will limit the amount of clipping as well.

So yes you will have some clipping, the amount of clipping can be modeled with PVwatts but will not be 2.255kW every hour

I am not sure why you though a 7.6kW inverter would NOT have a hard limit at 7.6kW. That is kind of what makes it a 7.6kW inverter...

Example of clipping on 5-22

So is this "normal" and to be expected? At what point should I request a 10 kW inverter instead of the 7.6 kW inverter?

2019-05-22 Capture.PNG

[barrye]

I have 11.2kw of pv panels in southern British Columbia and a 7.6 ev inverter.
I expected to get clipping when I installed it. On a sunny day i draw a straight line at 7.6 kw from 10am till 4pm.
I installed the 7.6 strictly for the EV portion.
I am waiting for the 11.4 kw EV inverter to come out and add a third string to my existing system.
I have to say I am happy with the 70 plus KWhours i am producing on sunny days

[ButchDeal]

Attempt #2 (copied from notepad to try to get whole posting in here)

My zip code is 60564

Here is what I found on the design doc:
AZIMUTH 180
TILT ANGLE 25

My SolarEdge 7600HD inverter does seem hard limited to 7600 AC output power. I was under the impression it could generate more, but it seems it can just take in more DC input and is limited to 7600 W AC output hard limit.

Here is the information for the two days where I saw a good amount of clipping (in my opinion):
5/22 59.44 kWh System production and 10:45am CT to 2:30pm CT clipped at 7600 W during that 3 hour 45 minute duration
5/23 46.16 kWh System production and 10:45am CT to 2:30pm CT clipped at 7600 W during that 3 hour 45 minute duration (Note: system was down during clipped time frame on 5/23 for 45 minutes due to some export/import monitoring configuration adjustments to make those functions work)

I do not think it is a shade issue for the clipping. I do have a chimney and it shades the panel on the left and right of it slightly during the day this time of year only, but not that much.

I had tried to get a 10000HD inverter installed but the installer convinced me that the 7600HD would be able to handle my system and that my clipping loss would be minimal. I'm not so sure that will be the case. I feel like June/July/August will have some nice sunny days where I lose almost 4 hours of 9.855 kW - 7.600 kW = 2.255 kW theoretically each hour (though I realize there will be loses in inverter conversion and the panels won't necessarily generate that full amount...though, they are 27 total LG 365 W panels all facing south, so I'm not sure...)

Any suggestions or comments on the above would be appreciated.

You can look at your graphs on the monitoring site and see that the production ramps up and down on a parabolic curve so you would NOT EVER have a solid block of clipping.
you PV modules are NOT going to produce the full DC STC rating especially in summer.
your shadows will limit the amount of clipping as well.

So yes you will have some clipping, the amount of clipping can be modeled with PVwatts but will not be 2.255kW every hour

I am not sure why you though a 7.6kW inverter would NOT have a hard limit at 7.6kW. That is kind of what makes it a 7.6kW inverter...

[Jeff72]

Jeff72: What's your zip and what's your array azimuth and tilt ? A PVWatts run can estimate your max. possible hourly output for sunny days by hour for an approx. reference.

7.6 kW output sounds low for a 9.9 kW array, and it's probably due to the inverter being undersized, especially if the output for 4 hrs. is dead flat at 7.6 kW. Was the reduced or flat output somewhat symmetric around solar noon +/- some ?

There's a small and quite unlikely chance the low output may be due to shading, but stranger things have happened. What was the daylong output in kWh for those two sunny days ?

Attempt #2 (copied from notepad to try to get whole posting in here)

My zip code is 60564

Here is what I found on the design doc:
AZIMUTH 180
TILT ANGLE 25

My SolarEdge 7600HD inverter does seem hard limited to 7600 AC output power. I was under the impression it could generate more, but it seems it can just take in more DC input and is limited to 7600 W AC output hard limit.

Here is the information for the two days where I saw a good amount of clipping (in my opinion):
5/22 59.44 kWh System production and 10:45am CT to 2:30pm CT clipped at 7600 W during that 3 hour 45 minute duration
5/23 46.16 kWh System production and 10:45am CT to 2:30pm CT clipped at 7600 W during that 3 hour 45 minute duration (Note: system was down during clipped time frame on 5/23 for 45 minutes due to some export/import monitoring configuration adjustments to make those functions work)

I do not think it is a shade issue for the clipping. I do have a chimney and it shades the panel on the left and right of it slightly during the day this time of year only, but not that much.

I had tried to get a 10000HD inverter installed but the installer convinced me that the 7600HD would be able to handle my system and that my clipping loss would be minimal. I'm not so sure that will be the case. I feel like June/July/August will have some nice sunny days where I lose almost 4 hours of 9.855 kW - 7.600 kW = 2.255 kW theoretically each hour (though I realize there will be loses in inverter conversion and the panels won't necessarily generate that full amount...though, they are 27 total LG 365 W panels all facing south, so I'm not sure...)

Any suggestions or comments on the above would be appreciated.

[Mike90250]

Typing is best accomplished using standard fonts. The "fancy" fonts trigger the anti-canned meat software and that truncates the post. phones, tablets and mac's are the worst offenders.

[Jeff72]

Jeff72: What's your zip and what's your array azimuth and tilt ? A PVWatts run can estimate your max. possible hourly output for sunny days by hour for an approx. reference.

7.6 kW output sounds low for a 9.9 kW array, and it's probably due to the inverter being undersized, especially if the output for 4 hrs. is dead flat at 7.6 kW. Was the reduced or flat output somewhat symmetric around solar noon +/- some ?

There's a small and quite unlikely chance the low output may be due to shading, but stranger things have happened. What was the daylong output in kWh for those two sunny days ?

My zip code is 60564

Here is what I found on the design doc:
AZIMUTH 180
TILT ANGLE 25

Do new member get limited on what we can post here? This board is cutting off like 90% of what I typed here. Lost all the response to your questions....sigh

[J.P.M.]

I just had a 9.855 kW panel system installed with the installer's recommended SolarEdge 7600HD inverter. I've seen two sunny days in the last week with just under 4 hours straight of clipping at 7600 W each day. I felt that I should have gotten a 10000HD inverter for my 9,855 W panel array. Should I insist on replacing the 7600HD inverter with the 10000HD or is there really a benefit with my system and will the clipping not affect things too bad with 7600HD?

Jeff72: What's your zip and what's your array azimuth and tilt ? A PVWatts run can estimate your max. possible hourly output for sunny days by hour for an approx. reference.

7.6 kW output sounds low for a 9.9 kW array, and it's probably due to the inverter being undersized, especially if the output for 4 hrs. is dead flat at 7.6 kW. Was the reduced or flat output somewhat symmetric around solar noon +/- some ?

There's a small and quite unlikely chance the low output may be due to shading, but stranger things have happened. What was the daylong output in kWh for those two sunny days ?

[Jeff72]

7600 requires a 40A breaker. (7600 / 240 * 1.25 = 40)
10000 will require a 60A breaker (10000 / 240 * 1.25 = 52; next size up == 60)

So you'll need a larger breaker, larger wire size from the panel to the breaker.
And that may require additional changes to the breaker panel (like changing to a supply-side tap, or replacing the breaker panel or ....)
We would need a lot more information about how your installation was done to tell you if this would be a fairly straightforward upgrade, or if it'd likely require significant work.
If it'd require significant work, then the benefit is you didn't have to pay for that work to be done. And that extra work/cost may not have had a reasonable payoff time (maybe even never)

They connected my system outside on the inside connection at the electric meter. Nothing goes inside the house besides the main feed and a cat5 cable for monitoring to my Internet router. So, I don't think any wiring will need to change. I would think a simple inverter swap might just work but i'm not sure.

Also, they have a solar array main shutoff before it connects to the outside electric meter. (Inverter is outside mounted to house)

Does that help answer your question?

Jeff

[foo1bar]

I just had a 9.855 kW panel system installed with the installer's recommended SolarEdge 7600HD inverter. I've seen two sunny days in the last week with just under 4 hours straight of clipping at 7600 W each day. I felt that I should have gotten a 10000HD inverter for my 9,855 W panel array. Should I insist on replacing the 7600HD inverter with the 10000HD or is there really a benefit with my system and will the clipping not affect things too bad with 7600HD?

7600 requires a 40A breaker. (7600 / 240 * 1.25 = 40)
10000 will require a 60A breaker (10000 / 240 * 1.25 = 52; next size up == 60)

So you'll need a larger breaker, larger wire size from the panel to the breaker.
And that may require additional changes to the breaker panel (like changing to a supply-side tap, or replacing the breaker panel or ....)
We would need a lot more information about how your installation was done to tell you if this would be a fairly straightforward upgrade, or if it'd likely require significant work.
If it'd require significant work, then the benefit is you didn't have to pay for that work to be done. And that extra work/cost may not have had a reasonable payoff time (maybe even never)

[Jeff72]

I just had a 9.855 kW panel system installed with the installer's recommended SolarEdge 7600HD inverter. I've seen two sunny days in the last week with just under 4 hours straight of clipping at 7600 W each day. I felt that I should have gotten a 10000HD inverter for my 9,855 W panel array. Should I insist on replacing the 7600HD inverter with the 10000HD or is there really a benefit with my system and will the clipping not affect things too bad with 7600HD?

[barrye]

8 awg/4 from the panels to the inverter 6awg/ from inverter to 50a breaker.
Not sure about meter to pole..
Fortunately when I put my application in to B C Hydro i had designed a system with a 10 kw inverter
and switched ( after much teeth gnashing) to the 7.6 EV charger.
Now my wife doesn't want to buy an electric car
c'est la vie

[Mike90250]

I have a 200 amp service.
Cable to breaker is 6awg/3.
Breaker is 50 amp as the EV part of the inverter
is set to 40 amps.
So far I have done my own wiring. Only had to redp it once (LOL)

I show 6ga wire as best case rated 75A Is this the wire gauge to your inverter, or to the EV outlet ?

Do you know the gauge and distance of your house hold feed wire from the electric company?

Adding an inverter may mean a change in your buy-back/net-meter contract and you may loose any currently favorable rates

[barrye]

I have a 200 amp service.
Cable to breaker is 6awg/3.
Breaker is 50 amp as the EV part of the inverter
is set to 40 amps.
So far I have done my own wiring. Only had to redp it once (LOL)