Did they wire up my system incorrectly?

[kman42]

I just had a 7.6 kW system installed, but I am concerned they wired it incorrectly. It passed inspection a few days ago and I and waiting for PTO. I turned it on to test it (and because I am excited). When I connect to the inverter (Tesla) over wifi, it says I have two active strings. The other two show low voltage and "(no MCI detected)". I thought I should have four strings active, so I opened up the inverter and started looking around. Here is how it is wired:

And here is the wiring diagram:

I'm no electrician, but it looks to me like they wired it as a 3.8 kW system with two combined strings. Can someone with more knowledge help me understand what's going on?

Thanks!

 

[jjrandorin]

Im not an electrician either, but what does the tesla app have for production, between 11am and 2pm? if its more than 3.8 your system cant be wired as such.

 

[kman42]

Im not an electrician either, but what does the tesla app have for production, between 11am and 2pm? if its more than 3.8 your system cant be wired as such.

The solar monitoring isn’t live on my Tesla app yet. I think they activate it after PTO.

 

[jjrandorin]

The solar monitoring isn’t live on my Tesla app yet. I think they activate it after PTO.

Who did your install? I havent heard of not being able to see production of a tesla system in the tesla app, after its installed, but perhaps thats a thing now? I would start by trying to see production first (I would have started with that before opening up wiring, personally).

 

[yblaser]

It could be fine. It really depends on how the panels are wired on the roof. You will need a copy of the install plans to determine that. Absent that, report what voltage and current the two strings are reporting on the inverter webpage.

 

[wwhitney]

I think it's clear from the wiring that only 3.8 kW of inverter have DC inputs connected. That might possibly be OK if it's a 7.6 kW DC system with half the panels facing east and half facing west.

Cheers, Wayne

 

[kman42]

Perfectly sunny, no obstructions or shade, and all panels are south facing. Here's what the web interface to the inverter is showing right now, a little after noon. The voltage on strings 3 and 4 do fluctuate a bit, but never go very high.

 

[VT_EE]

Perfectly sunny, no obstructions or shade, and all panels are south facing. Here's what the web interface to the inverter is showing right now, a little after noon. The voltage on strings 3 and 4 do fluctuate a bit, but never go very high.

View attachment 858963

Looks like you are good. 5.8kW is probably all you will get this time of year depending on the angle of sun incidence.

 

[kman42]

Okay. So that 5.8kW is the actual solar production?

 

[jjrandorin]

Okay. So that 5.8kW is the actual solar production?

It looks like actual production to me (the production that was occurring when the screenshot was taken). I dont know why it says "todays production 0.0" though, as I havent seen that screen before (I dont have that equipment).

I can say, however, that my 8.6kW PV is generating 5.3kW right now. Im north of you, in Temecula, and we obviously have different system sizes, houses, etc, but if your system is generatinng 5.8kW right now then I dont see any issue with it.

 

[taphil]

You have two independent strings on the roof. Each string has half the panels wired in series. Then they are wired together (combined) in parallel on the roof, so just one set of wires comes down into the inverter. Same setup as me.

Yesterday, perfectly sunny on nearly perfectly angled and pitched roof, I maxed out at 6.5kW up in LA.

 

[kman42]

Thank you all! I feel better about it now and can’t wait to get my production on the Tesla app and PTO. And my MY in Nov-Dec

 

[taphil]

For completeness, if you know what panels were installed, you can do the math to be assured the production and wiring are correct.

For example, my 8.16kW system has 24 Q.Cell Peak Duo 340W panels. At ideal conditions, they produce ~34V at 10A.
Each independent string is 12 panels. When wired in series, the string produces 12 x 34V = 408V x 10A (current stays the same) = 4080W.
When each string is combined in parallel, voltage stays the same at 408V and amps are combined to 20A, so 408V x 20A = 8160W.

The inverter splits them up again across 2 MPPT using the jumper wires you have installed, and your production values match relative to the time of year, roof angle, and pitch.

On a 78F cool day in mid spring, I do hit 7.6kW production.

 

[wwhitney]

I think it's clear from the wiring that only 3.8 kW of inverter have DC inputs connected.

Obviously from the app info, the above is wrong, so I looked at the spec sheet. Each MPPT input can do 60-480VDC at up to 13A. So you don't have to use all 4 inputs in order to get 7.6 kWDC in; at the 305V string voltage the OP has, that's just 25A, so splitting it across 2 inputs should work. [And max Isc per input is 15A, so there's some leeway for the temperature-corrected max Isc.]

Cheers, Wayne

 

[haali77]

I just had a 7.6 kW system installed, but I am concerned they wired it incorrectly. It passed inspection a few days ago and I and waiting for PTO. I turned it on to test it (and because I am excited). When I connect to the inverter (Tesla) over wifi, it says I have two active strings. The other two show low voltage and "(no MCI detected)". I thought I should have four strings active, so I opened up the inverter and started looking around. Here is how it is wired:

View attachment 858920




View attachment 858921



And here is the wiring diagram:

View attachment 858922


I'm no electrician, but it looks to me like they wired it as a 3.8 kW system with two combined strings. Can someone with more knowledge help me understand what's going on?

Thanks!

Did your solar production changed after PTO?

 

[kman42]

Well, they got that part right as explained by someone else in this thread and I’m producing as expected, but they put the sensors on the wrong wires so my monitoring is messed up. Not a big deal as SDG&E seems to know the correct energy flow but the app shows me screwy data. I’ve had a support ticket in for two weeks. They were very responsive when I first called and told me it would be about three weeks before they could get back to me with a resolution, so I’m cutting them some slack until next week. Otherwise, the system is great.