Low Solar Production and Peak vs Rated

[v4556]

I have a new 8.4 Kw Tesla Solar Panel system (21 panels) with 2 PW+. It's been up and operational for over 2 months. The peak solar production I've ever seen this system produce is 5.6Kw and a total of 35.6Kwh so far. I live in Texas and we've had some pretty good sunny days and this is the peak I've seen this system generate. Is this normal? There are no obvious obstructions and the system is facing South (13 panel string) and West (8 Panel string).

I used PyPowerwall to start digging into see if both strings are generating power properly and this is what I got from the string data:

{'A': {'Current': 9.11, 'Voltage': 271.2, 'Power': 2449.0, 'State': 'PV_Active', 'Connected': True},

 'B': {'Current': 9.01, 'Voltage': 270.3, 'Power': 2400.0, 'State': 'PV_Active_Parallel', 'Connected': True},

 'C': {'Current': 0.0, 'Voltage': -1.0, 'Power': 0.0, 'State': 'PV_Active', 'Connected': False},

 'D': {'Current': 0.01, 'Voltage': -1.299999999999999, 'Power': 0.0, 'State': 'PV_Active', 'Connected': False}

 }

Is it normal for the state of the second string to be 'PV_Active_Parallel'? Some of the other discussions I've seen on this forum have state as 'PV_Active'. Anyone familiar what parallel means for state of the string? And if this string data makes sense to you?

 

[SageBrush]

The two strings are in parallel. That is fine.

As for production, report the panel inclinations. Are the panels in each string the same inclination ?

Your peak is probably fine, since there is not a lot of overlap between west and south. Peak from the south facing array would be ~ 400*13 = 5200 watts.

Do you know a little trig ? If so, grab a solar map from U. of Oregon and you will be able to calculate peak power any time you want. Just walk outside and convince yourself that none of the panels are shaded. If any shade is on a panel, calculate as if that entire panel is not generating.

 

[wwhitney]

With 21 panels, I don't see how you can have 2 strings in parallel. I can see 3 strings in parallel, of 7 panels each. Or with two separate inputs (not clear on the PW+ PV inverter details), one input with 1 string of 7 and another input with 2 strings of 7 in parallel.

But with 13 on one plane and 8 on the other (vs 14 and 7), seems like it should be one string of 13 and one of 8, assuming those are within the allowable string lengths. Putting panels in series with different orientations seriously hampers production, won't it?

Cheers, Wayne

 

[v4556]

Here's the wiring inside the inverter.

For a view of the panels and inclination:

 

[v4556]

The two strings are in parallel. That is fine.

As for production, report the panel inclinations. Are the panels in each string the same inclination ?

Your peak is probably fine, since there is not a lot of overlap between west and south. Peak from the south facing array would be ~ 400*13 = 5200 watts.

Do you know a little trig ? If so, grab a solar map from U. of Oregon and you will be able to calculate peak power any time you want. Just walk outside and convince yourself that none of the panels are shaded. If any shade is on a panel, calculate as if that entire panel is not generating.

The roof pitch for the south side is 42 and for the west side is 40.

 

[SageBrush]

I take it back -- these strings are not wired in parallel. I think each string is handled separately by the inverter. The log is mislabeled.

The inclination looks pretty steep. Good for year-round production, not so much for peak values.

OP: your question is probably whether the found values are consistent with a properly functioning array. I think so.

 

[v4556]

I take it back -- these strings are not wired in parallel. I think each string is handled separately by the inverter. The log is mislabeled.

The inclination looks pretty steep. Good for year-round production, not so much for peak values.

OP: your question is probably whether the found values are consistent with a properly functioning array. I think so.

It looks like I have two strings (String A connected in series and String B connected in parallel). Is it possible that one of the rows in String B that is connected in parallel is improperly connected or that row of panels is not working/producing? Just trying to rule out obvious issues.

 

[wwhitney]

The part I don't understand is that the reported voltages are equal, which means equal string lengths. Hence my suggestion of 1x7 and 2x7.

Also, I'm not sufficiently familiar with the wiring inside the inverter to tell what's going on, but you could try to trace it (visually) and match it up with one of the wiring configurations on the label.

Cheers, Wayne

 

[slcasner]

The part I don't understand is that the reported voltages are equal, which means equal string lengths. Hence my suggestion of 1x7 and 2x7.

But the currents are equal, too, so that suggestion isn't a complete answer, either.

 

[Laketime]

I would also say that that chimney must do some serious shading past 1-2pm.

 

[v4556]

I would also say that that chimney must do some serious shading past 1-2pm.

It tends to cover one panel past 2 pm. I believe they took that into account and might have done a parallel configuration to compensate for that. Not 100% sure. But I should see a peak before 2pm and that hasn’t crossed 5.6kw yet.

 

[patrick40363]

I have a new 8.4 Kw Tesla Solar Panel system (21 panels) with 2 PW+. It's been up and operational for over 2 months. The peak solar production I've ever seen this system produce is 5.6Kw and a total of 35.6Kwh so far. I live in Texas and we've had some pretty good sunny days and this is the peak I've seen this system generate. Is this normal? There are no obvious obstructions and the system is facing South (13 panel string) and West (8 Panel string).

I used PyPowerwall to start digging into see if both strings are generating power properly and this is what I got from the string data:

{'A': {'Current': 9.11, 'Voltage': 271.2, 'Power': 2449.0, 'State': 'PV_Active', 'Connected': True},

 'B': {'Current': 9.01, 'Voltage': 270.3, 'Power': 2400.0, 'State': 'PV_Active_Parallel', 'Connected': True},

 'C': {'Current': 0.0, 'Voltage': -1.0, 'Power': 0.0, 'State': 'PV_Active', 'Connected': False},

 'D': {'Current': 0.01, 'Voltage': -1.299999999999999, 'Power': 0.0, 'State': 'PV_Active', 'Connected': Fals
 }

Is it normal for the state of the second string to be 'PV_Active_Parallel'? Some of the other discussions I've seen on this forum have state as 'PV_Active'. Anyone familiar what parallel means for state of the string? And if this string data makes sense to you?

I have a new 8.4 Kw Tesla Solar Panel system (21 panels) with 2 PW+. It's been up and operational for over 2 months. The peak solar production I've ever seen this system produce is 5.6Kw and a total of 35.6Kwh so far. I live in Texas and we've had some pretty good sunny days and this is the peak I've seen this system generate. Is this normal? There are no obvious obstructions and the system is facing South (13 panel string) and West (8 Panel string).

I used PyPowerwall to start digging into see if both strings are generating power properly and this is what I got from the string data:

{'A': {'Current': 9.11, 'Voltage': 271.2, 'Power': 2449.0, 'State': 'PV_Active', 'Connected': True},

 'B': {'Current': 9.01, 'Voltage': 270.3, 'Power': 2400.0, 'State': 'PV_Active_Parallel', 'Connected': True},

 'C': {'Current': 0.0, 'Voltage': -1.0, 'Power': 0.0, 'State': 'PV_Active', 'Connected': False},

 'D': {'Current': 0.01, 'Voltage': -1.299999999999999, 'Power': 0.0, 'State': 'PV_Active', 'Connected': False}

 }

Is it normal for the state of the second string to be 'PV_Active_Parallel'? Some of the other discussions I've seen on this forum have state as 'PV_Active'. Anyone familiar what parallel means for state of the string? And if this string data makes sense to you?

What size is the inverter?

 

[yblaser]

You said you had 2 PW+. Do you have two inverters?

 

[v4556]

What size is the inverter?

I believe the Tesla pw+ inverter is a 7.6 Kw

 

[v4556]

You said you had 2 PW+. Do you have two inverters?

No. 1 inverter.

 

[dareed1]

I simulated for lat 29.4 and long 98.5 with inclination 42degrees, assuming directly south and west.

This assumes no shade and no clouds, so after 2PM the south and combined curves won't look like the graph. But you should get around 6.5kW at 1:30PM if the system is working correctly.

I suspect that they have run two strings of 13 and 8 panels, input these into two MPPT channels, but jumpered the two channels together. This effectively puts the two strings in parallel, resulting in the PV voltage set by approximately the lower of the two string voltages. In this configuration, the current in the two channels will also be nearly equal as long as the two channels are running MPPT correctly. Until your chimney shades several of the south facing panels, the string voltage will be the that of the west facing string, which will be in the neighborhood of 8*35=280VDC, assuming your panels are similar to the 405watts Q.PEAK GL-10+.

Tesla ran this experiment for me, first by hard wiring our two strings in parallel, then separating them but again effectively placing them in parallel by placing a jumper across the two MPPT channels. So I'm pretty sure about the behavior you'll get if they did in fact arrange the two strings to be either hard wired or jumpered to parallel. The power will be the string voltage times the sum of the two MPPT channel currents, and that's what you're evidently seeing.

It took about 2 months (one year ago) to obtain fully independent operation of the two strings at our house, comprising 3 service calls.

 

[v4556]

I simulated for lat 29.4 and long 98.5 with inclination 42degrees, assuming directly south and west. View attachment 799342

This assumes no shade and no clouds, so after 2PM the south and combined curves won't look like the graph. But you should get around 6.5kW at 1:30PM if the system is working correctly.

I suspect that they have run two strings of 13 and 8 panels, input these into two MPPT channels, but jumpered the two channels together. This effectively puts the two strings in parallel, resulting in the PV voltage set by approximately the lower of the two string voltages. In this configuration, the current in the two channels will also be nearly equal as long as the two channels are running MPPT correctly. Until your chimney shades several of the south facing panels, the string voltage will be the that of the west facing string, which will be in the neighborhood of 8*35=280VDC, assuming your panels are similar to the 405watts Q.PEAK GL-10+.

Tesla ran this experiment for me, first by hard wiring our two strings in parallel, then separating them but again effectively placing them in parallel by placing a jumper across the two MPPT channels. So I'm pretty sure about the behavior you'll get if they did in fact arrange the two strings to be either hard wired or jumpered to parallel. The power will be the string voltage times the sum of the two MPPT channel currents, and that's what you're evidently seeing.

It took about 2 months (one year ago) to obtain fully independent operation of the two strings at our house, comprising 3 service calls.

Thank you very much for this info. I am noticing the same phenomenon you described about both strings reporting almost equal current and voltage. My panels are Tesla panels (changed by Tesla from Q.Cells to Tesla panels a week before installation).

I have a service request open with Tesla right now. Can you tell exactly what I should ask Tesla to get both strings achieve independent operation to produce maximum power?

 

[dareed1]

My experience, which is now more than a year old, suggests that it is important to concisely explain the important symptoms. Simply telling Tesla that you expected more energy or peak power output than you're seeing will probably not get a good response. In this case I would write an email to the service operation and include the JSON output from your head post, the fact that you have a 8 panel west facing and south facing 13 panel layout, and mention that the expected voltage from the 13 panel string should be at least 440V. Of course if you already have a service ticket number, include that as well. One other thing that would be helpful is if you could tell them how the system is wired now, but unless you are quite familiar with electronic matters and also spend some time peering at the maze of wires, you may not be able to see how it is wired.

The idea here is to provide to a technical person the information needed to see with just a quick glance that the system is not working correctly .

Then you'll need to call and call, referring to your email, being polite but firm that the system voltages and currents clearly show the system is not functioning correctly. Tiresome, but until the issue is escalated and somebody with good technical knowledge sees the data, they won't recognize that there is a problem. Apparently the main responsibility of the the team answering the phones is to try to dismiss the issue, and you've got to get past that. And, in order to get service sooner than later, you've got to be persistent.

When I was getting our system resolved it turned out that technical folks had access to the text of of my emails, but not to the attachments. Also, at that time, there were two groups of technical folks, one for PWs and a second for inverters and other solar stuff. Our problem was initially escalated to the wrong group. Perhaps the organizational structure is different now.

 

[v4556]

My experience, which is now more than a year old, suggests that it is important to concisely explain the important symptoms. Simply telling Tesla that you expected more energy or peak power output than you're seeing will probably not get a good response. In this case I would write an email to the service operation and include the JSON output from your head post, the fact that you have a 8 panel west facing and south facing 13 panel layout, and mention that the expected voltage from the 13 panel string should be at least 440V. Of course if you already have a service ticket number, include that as well. One other thing that would be helpful is if you could tell them how the system is wired now, but unless you are quite familiar with electronic matters and also spend some time peering at the maze of wires, you may not be able to see how it is wired.

The idea here is to provide to a technical person the information needed to see with just a quick glance that the system is not working correctly .

Then you'll need to call and call, referring to your email, being polite but firm that the system voltages and currents clearly show the system is not functioning correctly. Tiresome, but until the issue is escalated and somebody with good technical knowledge sees the data, they won't recognize that there is a problem. Apparently the main responsibility of the the team answering the phones is to try to dismiss the issue, and you've got to get past that. And, in order to get service sooner than later, you've got to be persistent.

When I was getting our system resolved it turned out that technical folks had access to the text of of my emails, but not to the attachments. Also, at that time, there were two groups of technical folks, one for PWs and a second for inverters and other solar stuff. Our problem was initially escalated to the wrong group. Perhaps the organizational structure is different now.

Do you know what Tesla had to do resolve your issue? Did they have to re-wire the inverter or panels ? Any info you could share will be helpful. Greatly appreciate the info you’ve been sharing.

 

[SageBrush]

Do you know what Tesla had to do resolve your issue

Look at the picture OP took of the schematic. The jumper was removed and each string was given its own channel. The inside of the box actually has explicit instructions to not combine strings of different panel number.

I'm still not sure that was done in this case because I do not expect each string to have the same current.