SE7600H clipping at 7.9KW

[sorka]

Anyones else's SE7600 clipping at 7.9 KW. Today I had a ton of cloud reflection resulting in output going up to and pegging at 7.9 KW and it stayed there even when the brightness climbed well above that. I then looked back on the historical data for all the other partly cloudy days and each time it hit 7.9 and never higher.

Could my inverter not be configured for the 120% above 7.6? I should be able to hit 9KW without clipping.

 

[Vines]

Anyones else's SE7600 clipping at 7.9 KW. Today I had a ton of cloud reflection resulting in output going up to and pegging at 7.9 KW and it stayed there even when the brightness climbed well above that. I then looked back on the historical data for all the other partly cloudy days and each time it hit 7.9 and never higher.

Could my inverter not be configured for the 120% above 7.6? I should be able to hit 9KW without clipping.

Unsure what your concern is here. The device is rated for 32A of output, and is outputting 32.9A if the assumed 240V is used to get amps out of your power.

What do you mean "Configured for 120% above 7.6?"

 

[jrweiss98020]

Spec sheet sez max continuous output current is 32A, which is 7680W @240V, so your reported 7.9KW is nominal.

 

[sorka]

Unsure what your concern is here. The device is rated for 32A of output, and is outputting 32.9A if the assumed 240V is used to get amps out of your power.

What do you mean "Configured for 120% above 7.6?"

The 7600 shouldn't clip until it's input hits 9120 watts.d

My system is 8.16 KW. It will easily exceed that in the summer on partly cloudy days when the sun is not blocked by clouds.

Shouldn't Tesla have given me an inverter big enough to not clip?

And indeed you're correct about the breaker size. Just checked the TEG and it's 40 amps which means this summer I'm going to have tons of clipping. I'm hitting 6.3 KW for an hour every day in the middle of the winter without any cloud reflection at all and somewhat dirty panels.

 

[Vines]

The 7600 shouldn't clip until it's input hits 9120 watts.

Based on what?

 

[h2ofun]

The 7600 shouldn't clip until it's input hits 9120 watts.

My SE 11.4K clips at 11.39 or so. So are you saying they should clip higher than spec?

 

[Ampster]

My 3.8 kW inverter clips right at 3.8 kW. I thought that is what 3.8 meant? Mine has a DC to AC ratio of 1.50 which means my panels are 150% of my inverter capacity. That number has nothing to do with configuration of the inverter, but only with configuration of the system.

 

[sorka]

My 3.8 kW inverter clips right at 3.8 kW. I thought that is what 3.8 meant? Mine has a DC to AC ratio of 1.50 which means my panels are 150% of my inverter capacity. That number has nothing to do with configuration of the inverter, but only with configuration of the system.

Then are you giving up 1/3rd of your PV potential? What's your PV system size?

 

[h2ofun]

Then are you giving up 1/3rd of your PV potential? What's your PV system size?

14.5K

 

[sorka]

14.5K

So do you have a lot of clipping in the summer? Is it expected to size the inverter that much smaller than the PV system size?

 

[sorka]

Oh, and why am I showing 7.9 when given the breaker size it should be 7.6?

 

[h2ofun]

So do you have a lot of clipping in the summer? Is it expected to size the inverter that much smaller than the PV system size?

I have been told max size PV to inverter is 133%, which mine is. Here is the worse case I say once with clipping. Not much

 

[sorka]

Maybe the extra heat in the summer will lower the panel efficiency enough that I don't see as much difference in middle of the day peak in winter vs summer. Currently making about 38kwh / day where I am when it's sunny with no clouds which some folks in another thread yesterday seem to think that's unusual for the time of year at my current latitude.

 

[Ampster]

Then are you giving up 1/3rd of your PV potential? What's your PV system size?

My panels are 5.7 kW. I had my installer do an analysis and the loss from clipping is offset by the earlier ramp up and longer output. In summer when panels are hot they put out less than cold panels. I agree, it graphically looks and feels like a haircut. In my case a bigger inverter would have meant bigger breaker and derating of my busbars. High DC to AC ratios are increasingly common.

 

[sorka]

Interesting article on inverter sizing and efficiency. If this still holds in the industry, then a larger inverter would have resulted in less overall production given the ramp up and down curves would be flatter more than making up for any clipping on top.

Sizing inverters to optimise solar panel system efficiency | Solar Choice

Still, it would all depend on individual setup and environment. Panels split east and west and none south will make a wider and flatter curve which would allow an even higher undersizing ratio.

All south facing but with morning and afternoon shade might favor a larger inverter to take advantage of peak (no clipping) when you're already obscured partially on the ramp up and down.

 

[h2ofun]

My panels are 5.7 kW. I had my installer do an analysis and the loss from clipping is offset by the earlier ramp up and longer output. In summer when panels are hot they put out less than cold panels. I agree, it graphically looks and feels like a haircut. In my case a bigger inverter would have meant bigger breaker and derating of my busbars. High DC to AC ratios are increasingly common.

When I split I am just going to go with two 11.4K SE inverters. Why not, I can get all the wiring, breakers, subpanels, etc sized to add anything in the future if I wanted to. Any reason this strategy is bad?

 

[h2ofun]

Interesting article on inverter sizing and efficiency. If this still holds in the industry, then a larger inverter would have resulted in less overall production given the ramp up and down curves would be flatter more than making up for any clipping on top.

Sizing inverters to optimise solar panel system efficiency | Solar Choice

View attachment 629807

I have always looked at that chart as would cannot hurt having too many panels, like I am up to the 133%. I have see no real negative to use a larger inverter other than it costs a few more bucks?

 

[sorka]

My panels are 5.7 kW. I had my installer do an analysis and the loss from clipping is offset by the earlier ramp up and longer output. In summer when panels are hot they put out less than cold panels. I agree, it graphically looks and feels like a haircut. In my case a bigger inverter would have meant bigger breaker and derating of my busbars. High DC to AC ratios are increasingly common.

Almost jinx. I was just reading about that while you were posting it

 

[Vines]

Oh, and why am I showing 7.9 when given the breaker size it should be 7.6?

Because likely your grid voltage is about 247vac, instead of 240v nominal. Rarely is the service voltage actually 240v, it depends where you are from the transformer.

 

[sorka]

Because likely your grid voltage is about 247vac, instead of 240v nominal. Rarely is the service voltage actually 240v, it depends where you are from the transformer.

That is indeed the case. It's exactly 247.

So being close to the transformer (ground based that sits about 300 feet away) is allowing me to extract more from my system than if it was 240 volts ?