Tesla installed strings in parallel on 7.6 Inverter

[Sun007]

7.6 Tesla inverter and 24 panels

All my panels - 24 are pointed south, but i have trees and shading on each side of the roof.
So i asked tesla to install at least 3 strings.
But they told me , since their pipe coming down is not thick enough- only for 4 cables, they have 3 strings, but 2 of which are combined on the roof , so net net , only 2 are coming down

Is this acceptable ?
How come other people can have more cables come down
What is the point of having inverter with 4 MPPTs but tesla cannot use them, as pipe are not thick enough.

 

[Sun007]

7.6 Tesla inverter and 24 panels


All my panels - 24 are pointed south, but i have trees and shading on each side of the roof.

So i asked tesla to install at least 3 strings.

But they told me , since their pipe coming down is not thick enough- only for 4 cables, they have 3 strings, but 2 of which are combined on the roof , so net net , only 2 are coming down



Is this acceptable ?

How come other people can have more cables come down

What is the point of having inverter with 4 MPPTs but tesla cannot use them, as pipe are not thick enough.

I have attached the line diagram which was received pre install. Did the installer follow what the Line diagrams say ?

 

[Vines]

If it's 3/4" EMT, then (10) #10 AWG wires will fit inside it, enough for at least EDIT 3 strings, probably more depending on the specifics of the modules.

Hard to understand why unless they run 1/2" emt? There is some consideration that strings of 8 vs strings of 12 might not be great as far as the voltage window, but as I don't have those specs in front of me I cannot cofirm.

 

[MCNE]

I think they can use them they just didn’t in your case. The conduit issue seems like an excuse. All of them are used on my 7.6 inverter.

 

[jjrandorin]

(moderator note)

Combined 2 threads started on same topic by OP. I cant delete the first post as it would delete the thread, and the second post has a line drawing the OP included, so I dont want to delete that one. I am just explaining why there are two posts from the OP, in one thread, and I havent deleted one of them.

 

[Sun007]

attaching picture
He said , panels r wired with 3 strings, but combined on roof to make it 2

But looking at picture, it looks like some combining is also done down in the inverter

 

[Ampster]

Is this acceptable ?

To me the question is what is the optimal cofiguration. A lot will have to do with the pattern of shade and how it strikes the strings. I don't have enough information to reach a conclusion. What I would do first is compare the projected output from PV Watts to the actual output of the system.

 

[Vines]

attaching picture
He said , panels r wired with 3 strings, but combined on roof to make it 2

But looking at picture, it looks like some combining is also done down in the inverter

Jumpers are connected to the channels 3 and 4 in your picture.

If you have only 1 set of wires coming down, you are connected to 1 mppt channel.

 

[Sun007]

To me the question is what is the optimal cofiguration. A lot will have to do with the pattern of shade and how it strikes the strings. I don't have enough information to reach a conclusion. What I would do first is compare the projected output from PV Watts to the actual output of the system.

Shading of branches happens on roof in morning one side and evening other side. Installation is done, i am running it all the time , but my car app does not show my inverter as of now. County inspection on Monday. I asked for solaredge or 3 strings . Got this. I am no expert in putting strings in parallel, but inverter is marketed as 4 MPTT. but not installed as even 3 MPPT

 

[Sun007]

Jumpers are connected to the channels 3 and 4 in your picture.

If you have only 1 set of wires coming down, you are connected to 1 mppt channel.

Attaching 1 more picture.
4 black wires are coming in .
2 reds cables in String 1+ and string 2+
2 Black cables in 1- and 4-
3 and 4 strings are combined

I don't understand this setup.
Can any one see the line diagram ( 2nd post picture ) and confirm is also supporting 2 strings only ?

 

[Vines]

Attaching 1 more picture.
4 black wires are coming in .
2 reds cables in String 1+ and string 2+
2 Black cables in 1- and 4-
3 and 4 strings are combined

I don't understand this setup.
Can any one see the line diagram ( 2nd post picture ) and confirm is also supporting 2 strings only ?

My mistake, I didnt see the bottom row has additional duplicate ports.

Looks like 2 strings to me, but your installer is who is responsible here. I do not install this inverter, or have experience with it.

 

[power.saver]

Attaching 1 more picture.
4 black wires are coming in .
2 reds cables in String 1+ and string 2+
2 Black cables in 1- and 4-
3 and 4 strings are combined

I don't understand this setup.
Can any one see the line diagram ( 2nd post picture ) and confirm is also supporting 2 strings only ?

From the portion of the plan you showed, there are two strings of panels on the roof (12 panels in each string). These are combined into one pair of wires running down to the inverter, where they are jumpered into two MPPT channels.

From the photos of the inverter, they ran two pairs of wires into the inverter, and these are probably one each for the two strings on the roof, with no combining of the strings on the roof. One of the two pairs is jumpered to a second MPPT channel in the inverter, for a total of three active MPPT channels.

It's not clear why they only jumpered one of the two strings in the inverter to an additional MPPT channel or if they even needed to.

The conduit appears to be 1/2" size, and you should be able to confirm that by looking at the plan in the detail for wiring run #2 (usually at the bottom, shows number of conductors and conduit size) or by measuring it yourself.

If it is 1/2" size conduit, then no more strings can be added. If it is larger, then you would be able to add a third string.

 

[sorka]

I would not have ordered Tesla solar if all they had at the time was their own inverter with no optimizer and panel level monitoring. Heck, not having a microinverter option was ALMOST a deal killer. I really didn't want a single point of failure inverter but at least the optimizers eliminate shading issues and allow me to see what each panel is making.

 

[wwhitney]

FWIW, putting two strings in parallel on a single MPPT is only going to negatively impact performance when the two strings have significantly different MPPT voltages. As long as the strings are the same length and orientation, only certain shading patterns will cause problems. Namely, when the optimal number of bypass diodes to be activated in each string differs, resulting in different MPPT voltages.

For example, if one string is completely unshaded, and one string is uniformly partially shaded, that's not a problem. All the PV cells involved are producing voltage; the partially shaded string will be producing less current, but Vmpp doesn't change much with insolation, so the two strings can operate at the same voltage reasonably efficiently.

But now suppose that one string is completely unshaded, and the other string has 1/4 of the panels illuminated at 40% and 3/4s of the panel illuminated at 80%. The latter string could either be operated with all panels producing voltage, and the current limited by the 40% illuminated panels, to provide 40% power. Or it could be operated with the less illuminated panels having their bypass diodes activated, so that only 3/4s of the panels are producing voltage, to produce 60% power. Which is what it would do on its own MPPT. But if it is paralleled with a fully illuminated string, it must operate at the same voltage with no bypass diodes activated, so it will end up producing only 40% power.

Cheers, Wayne

 

[Ampster]

I am no expert in putting strings in parallel, but inverter is marketed as 4 MPTT. but not installed as even 3 MPPT

Again, without data about production we have no clue about how close you are to optimal performance. The goal of any design in not to fill up each MPPT input but to design string size to the optimally match the string voltages to the inverter. As @wwhitney mentioned, putting two strings in parallel does not negatively impact performance unless shading results in significant voltage differences.

 

[FurryOne]

I'm really beginning to wonder where the engineers at Tesla got their degrees. I have a 24 panel setup - 12 East, & 12 West, with no shading, yet while they series wired the East side, they parallel wired the West side. (On the West side they split the panels 6/6, only 1 foot apart for a vent.) I asked why they didn't just do both series and the answer was "The engineer drew it that way." Of course, this is just part of my problems - Unconnected arrays, DC Arc Faults, and now the System won't even power up, showing inverter problems. (And no indication what they plan to do about it or when they'll return to fix it.)

 

[Sun007]

Adding to the original story

I have 24 panels.

What is the maximum number of panels into one string , which can go into one MPPT ?

Tesla says , they have divided into 3 groups using 2 mppts

One string is purely serial, with one has 2 parallel substrings

I think i read , one string cannot have more than 12 panels?????

So instead of doing 8+8+8 , as requested, i think they have done 12+(6+6) = which geometry wise makes on sense on a 4by6 Array, to avid shadding

 

[Sun007]

Short story is
Order Solar in April
. Tesla approved design with solaredge due to shading issues
Tesla changed inverter to Tesla Inc
I requested 3 strings for shading
They agreed , but They installed only 2
They asked payment.
I have refused
Stalemate now....

 

[SilverSp33d3r]

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.

 

[Bitslizer]

To OP Post your solar noon inverter system status for string voltage and amp. That will tell you how the panels are wired on the roof, as in how many panel in a series and if any string are parallel