Continuing my education - String Sizing

[kingofbanff]

Outback used to have a string sizing tool online but instead of hosting it they changed it to a download that I can't get to work...so...

My panels are 54.7V and 5.98 amps. The 3 Flexmax 80 charge controllers have a max input voltage of 150VDC.

Question 1) does this mean that I can wire in series a max of two panels in a string then have to start wiring the strings in parallel? Two panels would be 110 VDC

The current layout has 10 panels at 110 degree Azimuth/14 pitch, 18 panels at 110degree/27 degree pitch and 12 panels at 290 degrees/27 degree pitch.

Question 2) should the panels be split into three groups and each fed to a separate charge controller? Or do the charge controllers get bunched together and you just feed them all? Given my different azimuths I won't have full production from all panels at the same time. So although I'm over panelled I shouldn't be load clipping.

Question 3) If I mix two panels from the flatter East group with the 12 West facing panels how much will that degrade my efficiency? (the reason I would allocate 14 panels to this charge controller is that they will produce less than the East facing ones)

Question 4) The difference in production from the 14 degree pitch to the 27 degree seems likely to be 10%. How bad would it be to mix these?

As always thanks and pardon my newbieness!

[sensij]

As long as the two panels you put in series have the same orientation (azimuth and tilt), you can combine those pairs freely. In a shade free installation, there would be very little loss from mixing pairs as you suggested. Make sure your wiring from the combiner to the charge controller is sized for the combined amperage.

Each charge controller needs to be fed separately.

[ButchDeal]

Question 2) should the panels be split into three groups and each fed to a separate charge controller? Or do the charge controllers get bunched together and you just feed them all? Given my different azimuths I won't have full production from all panels at the same time. So although I'm over panelled I shouldn't be load clipping.

Question 3) If I mix two panels from the flatter East group with the 12 West facing panels how much will that degrade my efficiency? (the reason I would allocate 14 panels to this charge controller is that they will produce less than the East facing ones)

Question 4) The difference in production from the 14 degree pitch to the 27 degree seems likely to be 10%. How bad would it be to mix these?

As always thanks and pardon my newbieness!

2) Yes you could combine your modules in groups and feed to each charge controller separatly.
3) you typically would not want to do this
4) this isn't too much of an issue given same azimuth, it is not optimal reasonable.

[jflorey2]

1) Yes max of two panels in series
2) Do not wire the inputs of charge controllers in parallel. Each should have its own set of panels.
3) A moderate amount. You will get the lowest power of the two. For example, of one is generating 300 and the other one is generating 140, you will get around 280 watts from both.
4) Not too bad. You'll lose power due to the issue above but not a lot.

[sensij]

I think with question 3 the OP is suggesting that the two panels on the east face are in series. That series pair would be in parallel with six series pairs on the west face. The losses should be very small. Same with question 4. As long as both the panels in the series pair have the same azimuth and tilt, those pairs can be combined in parallel in whatever way is most convenient without incurring meaningful losses (except to the extend shade is involved).

[kingofbanff]

2) Do not wire the inputs of charge controllers in parallel. Each should have its own set of panels.

Thanks for your answers! I don't quite follow on question two.
I will have 12 to 14 modules per charge controller. So call it seven strings of two modules per controller. Would I not wire the seven strings in parallel and then put into a charge controller?

Or are you just making sure I don't wire the charge controllers in parallel and then just feed everything from all 40 panels in at once?

[kingofbanff]

Here is the roof layout. The southern part of the roof has 18 modules (only 16 are drawn) facing 110 azimuth and 12 modules facing 290, all on 27 degree tilt. The northern section has the ten modules at 110 azimuth and 14 angle tilt.

I'm thinking wire the 12 west (290) facing modules into one controller. Then wire 14 of the east (110) 27° tilt modules into the second controller. The third controller will get four modules from the 27° tilt plus the 10 modules from the 14° tilt (all facing 110).

So the west facing strings feeding charge controller number one will be consistent. The east facing strings feeding charge controller number two will also be consistent.
Charge controller three will be receiving some power from strings on a 27° tilt and some strings on a 14° tilt. This will be the inconsistent ones.
Thoughts?

[jflorey2]

Or are you just making sure I don't wire the charge controllers in parallel and then just feed everything from all 40 panels in at once?

Yes. Each subset of panels should feed its own charge controller without interconnecting on the panel side.

[kingofbanff]

Got it. Thanks.