Tesla installed strings in parallel on 7.6 Inverter

[Bitslizer]

I unfortunately didn’t catch a similar issue in my design. I had 36 panels installed in July, 18 on main house and 18 on my detached garage.
I have two tesla 7.6 inverters based on my powerwall+ units.

tesla engineering decided to do the following:

2 mppts on main house
10 panels in series facing east
8 panels in series facing west

for detached garage I have 2 mppts with one jumpered similar to the op to effectively make “3 mppts”
8 facing east
8 facing west
2 facing south
However to save on wire they combined the east and west panes into one set of wires to pull through the underground conduits and as mentioned jumpered the mppt at the inverter. I believe this is causing pretty significant system losses in the morning and evening but tesla is turning a blind eye. Unfortunately once the system has been installed tesla just doesn’t care and will ignore the design flaw. In addition to this since day 1 the two panel pane does not produce power and has a ground fault. Still battling for them to fix that.

So from my experience, stand your ground until they design the system as you want it to be. If I would have caught this design failure earlier I would have declined installation until fixed.

You would be surprised, a east west parallel string the lost is minimal. Voltage is largely the same for east west string through most of the day except near sun rise and sun set. Big difference in voltage is when lost happens. See the link at bottom

Have you try rebooting the inverter for the 2 panels inverter near solar noon? Sometime morning moisture that dry out after a while would work after a restart at noon. At least that may help troubleshoot if it works after a restart at noon.

https://www.fronius.com/~/downloads...ntated_PV_systems_with_one_MPP_Tracker_EN.pdf

 

[yblaser]

You would be surprised, a east west parallel string the lost is minimal. Voltage is largely the same for east west string through most of the day except near sun rise and sun set. Big difference in voltage is when lost happens. See the link at bottom

Have you try rebooting the inverter for the 2 panels inverter near solar noon? Sometime morning moisture that dry out after a while would work after a restart at noon. At least that may help troubleshoot if it works after a restart at noon.

https://www.fronius.com/~/downloads/Solar Energy/Technical Articles/SE_TA_Efficient_East_West_orientated_PV_systems_with_one_MPP_Tracker_EN.pdf

I agree having the two strings in parallel is probably not a huge efficiency loss unless there is uneven shading on the strings. That said it's silly that Tesla didn't spend the extra 10s of dollars to run an extra set of wires from the roof. If there is shading the efficiency loss could be significant.

 

[SilverSp33d3r]

You would be surprised, a east west parallel string the lost is minimal. Voltage is largely the same for east west string through most of the day except near sun rise and sun set. Big difference in voltage is when lost happens. See the link at bottom

Have you try rebooting the inverter for the 2 panels inverter near solar noon? Sometime morning moisture that dry out after a while would work after a restart at noon. At least that may help troubleshoot if it works after a restart at noon.

https://www.fronius.com/~/downloads/Solar Energy/Technical Articles/SE_TA_Efficient_East_West_orientated_PV_systems_with_one_MPP_Tracker_EN.pdf

You would be surprised, a east west parallel string the lost is minimal. Voltage is largely the same for east west string through most of the day except near sun rise and sun set. Big difference in voltage is when lost happens. See the link at bottom

Have you try rebooting the inverter for the 2 panels inverter near solar noon? Sometime morning moisture that dry out after a while would work after a restart at noon. At least that may help troubleshoot if it works after a restart at noon.

https://www.fronius.com/~/downloads/Solar Energy/Technical Articles/SE_TA_Efficient_East_West_orientated_PV_systems_with_one_MPP_Tracker_EN.pdf

Interesting paper thanks for the source. I have a slightly different issue as it’s east/ west with two different pitches for each set of 8 panels due to a pitch change on the roof. I can’t find any conclusive evidence to prove one way or another. Essentially I am going by the limited production from this specific inverter compared to the main house.
Currently it shows since July 19th main house inverter has produced 1400kWh. Detached garage inverter has produced 792 kWh. Both were activated at exactly the same time, I expected lower production with two panels not working but not close to 50% reduction.
As far as resetting the inverter, yes I’ve tried at all different hours, each time when it goes through the 6 steps it has a ground fault for that string, it still baffles me Tesla does not see this remotely.

It got to the point where I sent a picture of the voltage on that string and I was being accused of tampering with the install.

 

[Bitslizer]

Interesting paper thanks for the source. I have a slightly different issue as it’s east/ west with two different pitches for each set of 8 panels due to a pitch change on the roof. I can’t find any conclusive evidence to prove one way or another. Essentially I am going by the limited production from this specific inverter compared to the main house.
Currently it shows since July 19th main house inverter has produced 1400kWh. Detached garage inverter has produced 792 kWh. Both were activated at exactly the same time, I expected lower production with two panels not working but not close to 50% reduction.
As far as resetting the inverter, yes I’ve tried at all different hours, each time when it goes through the 6 steps it has a ground fault for that string, it still baffles me Tesla does not see this remotely.

It got to the point where I sent a picture of the voltage on that string and I was being accused of tampering with the install.

What do the system status screen for BOTH inverter read (volt, amp) for each string at around solar noon

Yeah, I agree 50% less production is alot!

 

[SilverSp33d3r]

What do the system status screen for BOTH inverter read (volt, amp) for each string at around solar noon

Yeah, I agree 50% less production is alot!

The voltage is dropped by 6v for the parallel e/west strings and they are producing about 1 amp less.

this is at about 2 pm I don’t have any reading at noon other than from the app. During the periods when sun is only on one side it’s greater.

 

[Bitslizer]

The voltage is dropped by 6v for the parallel e/west strings and they are producing about 1 amp less.

this is at about 2 pm I don’t have any reading at noon other than from the app. During the periods when sun is only on one side it’s greater.

The 6v is not much all things considered.... The 1 lower amp is more concerning. Do you know what awg wires they used for the underground run and how far was that run? A long run may account for the voltage drop

How does the roof pitch compare between 8 panels on the main house, vs the east and the west on the garage? Any chance the garage is overall/average steeper than the house? That may affect the amp part

 

[SilverSp33d3r]

The 6v is not much all things considered.... The 1 lower amp is more concerning. Do you know what awg wires they used for the underground run and how far was that run? A long run may account for the voltage drop

How does the roof pitch compare between 8 panels on the main house, vs the east and the west on the garage? Any chance the garage is overall/average steeper than the house? That may affect the amp part

From the j/b on roof of garage to the inverter it’s about 25 ft underground +/- 15 ft for the up/down (total wire is about 40ft) of 8awg stranded copper.
Pitch is 25 on main house and garage except as mentioned before the garage has 4 at 25 and 4 at 22 due to a pitch change.

 

[yblaser]

The voltage is dropped by 6v for the parallel e/west strings and they are producing about 1 amp less.

this is at about 2 pm I don’t have any reading at noon other than from the app. During the periods when sun is only on one side it’s greater.

At the time of your reading your garage panels are producing 82% less power than your house panels. A little more than half that difference is due to the two panel string not functioning. Taking those panels out of the analysis you are only seeing ~7% drop in power between the house and garage. This certainly doesn't explain the 50% difference in energy production. Might want to repeat this measurement several times throughout the day to see if there is enough difference in power to explain the energy differential.

 

[Bitslizer]

At the time of your reading your garage panels are producing 82% less power than your house panels. A little more than half that difference is due to the two panel string not functioning. Taking those panels out of the analysis you are only seeing ~7% drop in power between the house and garage. This certainly doesn't explain the 50% difference in energy production. Might want to repeat this measurement several times throughout the day to see if there is enough difference in power to explain the energy differential.

You meant 82% of the house? Not 82% "less"

2792w vs 3396w

The missing 2 panels will be another about 400w (south facing more 15% efficient?)

3200 vs 3396

Get a difference about 9.4%

 

[yblaser]

You meant 82% of the house? Not 82% "less"

2792w vs 3396w

The missing 2 panels will be another about 400w (south facing more 15% efficient?)

3200 vs 3396

Get a difference about 9.4%

Yes, thanks for the correction. Unfortunately can't edit my post.

 

[SilverSp33d3r]

You meant 82% of the house? Not 82% "less"

2792w vs 3396w

The missing 2 panels will be another about 400w (south facing more 15% efficient?)

3200 vs 3396

Get a difference about 9.4%

Yep this is accurate. Looking thru API data I think I found where the lack of production came from. It looks like there was a period of time that one inverter was disabled. I am missing those two panels though, and as mentioned each array is off by about 500w at peak.

 

[Bitslizer]

Yep this is accurate. Looking thru API data I think I found where the lack of production came from. It looks like there was a period of time that one inverter was disabled. I am missing those two panels though, and as mentioned each array is off by about 500w at peak.

The voltage drop for 8awg wire over 40-50 ft should not be an issue, the ampacity looks good too. At a lost of why such a big difference between the house and garage even after accounting for the 2 less panels. Any shading at all?

 

[SilverSp33d3r]

The voltage drop for 8awg wire over 40-50 ft should not be an issue, the ampacity looks good too. At a lost of why such a big difference between the house and garage even after accounting for the 2 less panels. Any shading at all?

One 70 ft palm tree. Trunk goes across array between 7:45-8:15. Summer it did not shade at all.
It looks like the garage array was turned off for about 2 weeks after install while the main house did not. After that two week hiatus the 2 panel array did not return, which also coincided with PTO.
I still don’t know why the two panel array is not working, I got on the roof yesterday and measured in the string combiner Box and all looked good, except that array only was outputting 10vac. I’m now waiting for tesla to get back for next steps.

 

[Sun007]

I am happy to say , after months of %$#^@ , i got my 3rd string
Data is
S1 : 8 panels: all shade shade 253 V / .6 amp
S2 : 8 panels half shaded 240 V / 1.5 amp
S3 : 8 panels panels : no shade 262 / 5.8 amp

 

[Sun007]

They also removed the jumper now between 3 and 4 mppts.
each string has its mppt now and 4th is empty

 

[Sun007]

Does any one know if with Tesla 8.2 kwh panels , if all panels are pointing south and ideally azimuthon , can clipping happen with 7.6 inverter ?
I am in DC latitude . Its just a feel good curiosity . I am excited about my all south facing roof...

 

[Bitslizer]

I am happy to say , after months of %$#^@ , i got my 3rd string
Data is
S1 : 8 panels: all shade shade 253 V / .6 amp
S2 : 8 panels half shaded 240 V / 1.5 amp
S3 : 8 panels panels : no shade 262 / 5.8 amp

Did they actually ran a new pair of wire down?

I think you may see a little bit clipping during June or July, but nothing to write home about

 

[Sun007]

Yes
And the results are in front of you, where same time, same orientation ...shading is making difference as published above
panel level is better ( original order ) than 4 string mppts vs 3 strings mppts vs 2 strings mppts

I just my feet down that i will not accept below 3 mppts for 24 panels period.

i think , I did the correct thing, as solar energy generation matters in a solar install. its not something to be unconcerned with.

i purchased a house specifically with large south facing roof with prefect angle, and look the "engineering design team" tried to install panels on the northside initially . nightmare for me. i did not seep well.

Like to hear what people think....if i was being unreasonable and demanding ....

 

[tdawg67]

I unfortunately didn’t catch a similar issue in my design. I had 36 panels installed in July, 18 on main house and 18 on my detached garage.
I have two tesla 7.6 inverters based on my powerwall+ units.

tesla engineering decided to do the following:

2 mppts on main house
10 panels in series facing east
8 panels in series facing west

for detached garage I have 2 mppts with one jumpered similar to the op to effectively make “3 mppts”
8 facing east
8 facing west
2 facing south
However to save on wire they combined the east and west panes into one set of wires to pull through the underground conduits and as mentioned jumpered the mppt at the inverter. I believe this is causing pretty significant system losses in the morning and evening but tesla is turning a blind eye. Unfortunately once the system has been installed tesla just doesn’t care and will ignore the design flaw. In addition to this since day 1 the two panel pane does not produce power and has a ground fault. Still battling for them to fix that.

So from my experience, stand your ground until they design the system as you want it to be. If I would have caught this design failure earlier I would have declined installation until fixed.

do you have 2 powerwall+ units for 36 panels? I have 36 panels, but 1 powerwall+ and additional powerwall2. My system is configured at 12kw, however, pre PTO, i see my solar power clamped at 7.6kw for 3-4 hours mid day, i have 3 mppts in use. Looking at the powerwall + spec sheet it looks like the max solar inverter power is 7.6kw, tesla claims this will get better once i recieve PTO but i don't see it in the spec sheet. I've gone thru the yearly estimations and if i'm truely limited at 7.6kw due to solar inverter i lose 5% of solar capacity thru the year due to clipping. Trying to figure out if my powerwall+ would support >7.6kw DC coming from 12kw array.

 

[Bitslizer]

Yes
And the results are in front of you, where same time, same orientation ...shading is making difference as published above
panel level is better ( original order ) than 4 string mppts vs 3 strings mppts vs 2 strings mppts

I just my feet down that i will not accept below 3 mppts for 24 panels period.

i think , I did the correct thing, as solar energy generation matters in a solar install. its not something to be unconcerned with.

i purchased a house specifically with large south facing roof with prefect angle, and look the "engineering design team" tried to install panels on the northside initially . nightmare for me. i did not seep well.

Like to hear what people think....if i was being unreasonable and demanding ....

Kudos to you actually to be able convince Tesla to re-wire for you. Usually once installed they won't change the design.