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New solar and Powerwall install, low production?

Mar 15, 2021
173
65
California
or they just flat out forgot to connect the second string. The output is not adding up they are actually in parallel. They clearly can't be in series since 24 of those modules would exceed the voltage input. Power production should be closer to 40 kWh for the day vs 20 kWh.
Yep. I also live in Los Angeles County and am currently producing 36 kWh with 19 panels, so they should definitely be closer to 40 kWh
 

nwdiver

Well-Known Member
Feb 17, 2013
7,983
10,342
United States
the should use all the mppt channels, as long as the voltage requirements can be met.

Longer strings are more efficient and more shade tolerant than short strings. Unless you're forced into it by roof layout it's better to have 24 panels in strings of 12 on 2 MPPT channels than in strings of 6 on 4.
 

taphil

Member
Apr 17, 2021
34
12
Los Angeles
I got a hold of my project advisor, he said only thing he can do is reach out to local install team. I asked for 2 strings of 12 panels in series to be wired up. I assume the missing string would connect to the 4+/4- port in the inverter? Question is, does it need the jumper to spread each string to two 2 channels?
 

nwdiver

Well-Known Member
Feb 17, 2013
7,983
10,342
United States
I got a hold of my project advisor, he said only thing he can do is reach out to local install team. I asked for 2 strings of 12 panels in series to be wired up. I assume the missing string would connect to the 4+/4- port in the inverter? Question is, does it need the jumper to spread each string to two 2 channels?

No. You don't want the jumper. Each channel can handle a string of 12 panels. The only reason you would need a jumper is if they don't run separate lines and try to keep them paralleled on the roof. I would advise pushing back on that. Request that they run another line set.

That's why the jumper is there... what they tried to do was combine 2 strings into 1 line on the roof then split that one line into 2 channels at the inverter. IMHO.... they were lazy or didn't understand the benefit of independent strings.

.... what makes this even more irritating from a professional perspective is that this problem would have taken ~10 seconds to see if they had run separate lines. Channel 1: 400v. Channel 2: 0v... Oooops... better fix that. But you don't get that benefit if the strings are combined on the roof. My last project was 12 strings. All of them run separately. Took me < 2 minutes to not only verify that all strings were connected but that all panels were connected since the voltage on each string was the correct voltage.
 
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sorka

Well-Known Member
Feb 28, 2015
8,042
5,867
Merced, CA
My identical system is producing 52 to 56 kwh / day in Merced, CA which is a bit north of where you are. I'm guessing you have one string not producing since it seems to be about half the expected output. My house is 205 south west, so it's even less optimal than your direction but only a tiny bit. My pitch is 25 degrees.

I'd never purchase a system where I can't monitor each and every panel. Aside from the fact that I couldn't do long term dust level buildup studies on different panels, I wouldn't be able to tell where a problem is with less than expected output.


Screenshot_20210421-095424_Tesla.jpgScreenshot_20210421-095401_Tesla.jpgScreenshot_20210421-095902_Gallery.jpg
 
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taphil

Member
Apr 17, 2021
34
12
Los Angeles
I got an email response from my project advisor. Basically it says:

(1) 2 stings are connected in parallel on the roof as designed, acceptable because all panels are located on same azimuth
(2) jumper wire between the two MMPT channels inside inverter is correct
(3) due to not having PTO, production numbers are inaccurate and they do not have production data available for analysis
(4) will reexamine production after PTO

So I will wait.

But in the meantime, let's assume 2 strings of 12 panels in series are connected in parallel. That means at theoretical peak production, the wires coming into the inverter should be 408V 20A. I'm curious as to what the inverter strings 1 and 2 will show after PTO, because as of now it's about 400V at 5A each. Is there like an "unlock" code the inverter receives from Tesla once system is paid for and PTO is granted?
 

sorka

Well-Known Member
Feb 28, 2015
8,042
5,867
Merced, CA
I got an email response from my project advisor. Basically it says:

(1) 2 stings are connected in parallel on the roof as designed, acceptable because all panels are located on same azimuth
(2) jumper wire between the two MMPT channels inside inverter is correct
(3) due to not having PTO, production numbers are inaccurate and they do not have production data available for analysis
(4) will reexamine production after PTO

So I will wait.

But in the meantime, let's assume 2 strings of 12 panels in series are connected in parallel. That means at theoretical peak production, the wires coming into the inverter should be 408V 20A. I'm curious as to what the inverter strings 1 and 2 will show after PTO, because as of now it's about 400V at 5A each. Is there like an "unlock" code the inverter receives from Tesla once system is paid for and PTO is granted?

3 is a lie. Having PTO has nothing to do with making sure the system is producing properly except that a properly working system needs to be in place BEFORE PTO. You're installer is required to make sure the system is functioning correctly BEFORE the inspection and BEFORE they even ask the utility for PTO.

Tesla made sure my system was producing the expected the day after my install AND the day of the county inspection.


Have you paid for the system yet? If not, I'd withhold payment until they fix your issue.
 
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sorka

Well-Known Member
Feb 28, 2015
8,042
5,867
Merced, CA
I paid with credit card. File dispute with credit card company is an option I guess.

To make it worse, you're approaching summer where you'll make most of your production for the year. If you end up suffering 12 week turn around times for Tesla to get things fixed like other customers have reported, that clock wouldn't even start ticking until after you get PTO.

PTO is the thing the utility grants you after you have a properly operating system installed and inspected.
 

mec37

Member
Apr 4, 2019
22
5
Boston
Ah.... that makes sense. I would have done 4 strings there too. SW String, SE String and the 14 panels facing NE is too many for 1 string... so 2 strings of 7.
So I'm a bit confused. The SE string is only 4 panels, but I thought each string on the Tesla inverter was supposed to have a minimum of 5 panels. Or is that just in cases where there is shade or otherwise lower sunlight that would cause the string to drop below the minimum input voltage of the inverter? (I'm in New England, which is why I ask the question.)
 

Rapidrezults

Member
Apr 18, 2021
8
6
Nor Cal
So I'm a bit confused. The SE string is only 4 panels, but I thought each string on the Tesla inverter was supposed to have a minimum of 5 panels. Or is that just in cases where there is shade or otherwise lower sunlight that would cause the string to drop below the minimum input voltage of the inverter? (I'm in New England, which is why I ask the question.)
This is exactly what I was interested in finding out. I posted a thread about it here: Panel/String Size Concerns with Tesla Inverter
 

sorka

Well-Known Member
Feb 28, 2015
8,042
5,867
Merced, CA
Also, just to be clear, are you able to see your production numbers in Tesla's app? If so, how can they tell you you don't have accurate production data simply because PG&E hasn't given you PTO. Granting PTO does nothing except makes it legal for you to operate your system. In order for them to grant PTO, your system must already be installed and configured. Mine was working the day of the install and I could see production numbers from that day forward.

You're even allowed to "test" your system prior to PTO to verify it's working and installed correctly.

What I didn't have access to until after PTO was Solar Edge's portal so I couldn't see panel level production until then. Also, I'd never buy a system that I can't get panel level production on and I'd never buy system that didn't either 1) have optimizers, or 2) micro inverters. Not having either means that if a panel on a string gets any shading, it brings the entire string down with it.
 

taphil

Member
Apr 17, 2021
34
12
Los Angeles
The "inaccurate data" due to PTO not yet granted is a Tesla excuse, it's been told to others here in the past when I did a search. I'm being told the same company line.

Tesla is only installing Tesla inverters, so I don't think anyone gets a choice on installing microinverters or another company's inverter. In my case, I own all the trees around my house that can ever grow tall enough to shade the panels, so that's not a problem.
 

sorka

Well-Known Member
Feb 28, 2015
8,042
5,867
Merced, CA
The "inaccurate data" due to PTO not yet granted is a Tesla excuse, it's been told to others here in the past when I did a search. I'm being told the same company line.

Tesla is only installing Tesla inverters, so I don't think anyone gets a choice on installing microinverters or another company's inverter. In my case, I own all the trees around my house that can ever grow tall enough to shade the panels, so that's not a problem.

Except that you'd never know when you have panel issues without being able to see panel by panel production. I guess it's a good thing I bought my solar late last year as I'd never have agreed to a Tesla inverter without panel level data.
 

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