Panel configuration disadvantages❓

[Wits' End]

If this is covered elsewhere, please direct me.
Advantages and disadvantages of series, parallel, wiring panels, when it comes to loss in one panel or a part of a panel. Due to external shadow, surface obstruction (bird droppings) or electrical issues.

I have 18 400W 50V OC BiFacial, and MPPT 250v 5000W max.
12 panels "East array" [side of roof, all same orientation] 4S3P
6 panels "West array" 3S2P, as yet unnamed MPPT SCC.

My main question, what are the disadvantages of the 4S3P? Would 3S4P be better? If part of array is shaded or not producing as highly.

2nd question: Does it make sense to run one of the 4S3P, parallel legs to a separate breaker? As under possible conditions, this array could produce in excess of 5000 watts, they are BiFacial.

Should I run positive and negative from PV, through breaker? Or just positive?

As I have two separate power runs from PV to SCC, I assume I have to put separate "lightning arrestors" on them.
LA are "better" than surge protection devices, at reducing damage from massive electrostatic discharges?

 

[Wits' End]

Does this all make sense? Is it about correct?
This is an electronically savvy friend's discussion with me (slowly getting it)

[5/30, 3:29 PM] Wits' End Phone: Ray: I see the new xxx phone is working.
The higher voltage isn’t the problem. By going with 4 panels you increase by 33% The chance to minimize the panel strings current. The current in the string is equal to the panel with the least current.
On the flip side you get greater power out with 4 panels. Since the current is the same with either 3 or 4 panels. The Power Loss thru the cable and is equal to the resistance of the wire times the current squared. 8 awg will give you less cable loss. With the panels on the roof how easy will it be to clean them or are you hoping Mother Nature (rain) will clean them.
[5/30, 3:29 PM] Wits' End Phone: If we can use 8 gauge the resistance lowers to .0315 and 6 gauge is .02 for 50 feet.
Sorry, BUT, that is for a single wire in open air. If you use conduit or multi wire bundle the resistance goes up because of it’s harder to dissipate the heat.
[5/30, 3:29 PM] Wits' End Phone: Ok! Thank You!
On the 'flip-flip' side... "Real world"... Unless one panel is producing less than the others all should be good. All panels have 5% dust, 10% bird dropping. All is not good but, equal losses. *BUT* if 1 panel in string has 66% loss due to hailstone, output of whole string is down 66%. If whole array is parallel does that cary through then?

Panel spec sheet

[5/30, 3:29 PM] Wits' End Phone: What you sent earlier helped a lot, I think.
So ~50V 11A max ideal
550 Watts? I'm going to use the 50+11 below, to make math simpler, if less accurate ? (42.5x9.65=410.1)

This is East array:
*4S3P 200V 33A 6600W* is better for resistive loss. Higher voltage, only "3 conductors" [6 if you count + & -]. {1pair 200v 22A, 1 pair 200V 11A} <note:under optimum conditions, I'll exceed my SCC input. Do I need to be able to kill extra, or will extra be ignored?>
*3S4P 150V 44A 6600W*
Higher resistive loss, "4 conductors" {1pair 150V 33A, 1 pair 150V 11A}

Assuming the array was running in 1 pair to SCC [Solar Charge Controller]
1 panel had a 60% drop, due to hail. 50/11 becomes 20/4.4
4s3p 170V/26.4. 4488W
3s4p. 120V/37.4 4488W
?????
[5/30, 3:29 PM] Wits' End Phone:Ray: Current in parallel is additive BUT because of higher current your loss thru the cable (resistance) is much greater. Formula is: Pwr loss = R x (amps)(amps).
For 50 feet of 10 AWG wire
R = .05 ohms
[5/30, 3:29 PM] Wits' End Phone: Unless the whole array drops to 4.4 amps, and there are no 11 amp additions

 

[Wits' End]

Looking for some "solar knowledgeable" input!

 

[snoobler]

If this is covered elsewhere, please direct me.
Advantages and disadvantages of series, parallel, wiring panels, when it comes to loss in one panel or a part of a panel. Due to external shadow, surface obstruction (bird droppings) or electrical issues.

I have 18 400W 50V OC BiFacial, and MPPT 250v 5000W max.
12 panels "East array" [side of roof, all same orientation] 4S3P
6 panels "West array" 3S2P, as yet unnamed MPPT SCC.

My main question, what are the disadvantages of the 4S3P? Would 3S4P be better? If part of array is shaded or not producing as highly.

The larger the voltage difference between PV and battery, the less efficient.

The higher the PV voltage, the less losses you have from wiring.

They pretty much wash out.

3S4P would be somewhat more tolerant of partial panel shading.

2nd question: Does it make sense to run one of the 4S3P, parallel legs to a separate breaker? As under possible conditions, this array could produce in excess of 5000 watts, they are BiFacial.

Code requires each series string of panels to have their own over-current-protection (OCP), i.e., each of your 4S strings should have their own breaker or fuse.

Should I run positive and negative from PV, through breaker? Or just positive?

Positive.

As I have two separate power runs from PV to SCC, I assume I have to put separate "lightning arrestors" on them.
LA are "better" than surge protection devices, at reducing damage from massive electrostatic discharges?

Allegedly. You don't see too many people using them, and I'm no expert on that.

 

[Hedges]

"[5/30, 3:29 PM] Wits' End Phone: If we can use 8 gauge the resistance lowers to .0315 and 6 gauge is .02 for 50 feet.
Sorry, BUT, that is for a single wire in open air. If you use conduit or multi wire bundle the resistance goes up because of it’s harder to dissipate the heat."

Don't worry too much about more power loss due to higher temperature. Copper resistance increases about 0.4%/degree C. But do use ampacity charts to make sure the wire won't become too hot for its insulation.


"<note:under optimum conditions, I'll exceed my SCC input. Do I need to be able to kill extra, or will extra be ignored?>"

Most MPPT can tolerate a PV array considerably above SCC wattage. It just ignores available extra power.
Never exceed max input voltage limit. If it lists maximum short circuit current, stay within that too.


"LA are "better" than surge protection devices, at reducing damage from massive electrostatic discharges?"

What do you mean by "LA"? Not a model from Delta, I hope. If that is what you mean, I've got some test results to show you (and Midnight has a couple videos.)

If you are in an area where nearby lightning strikes are common, then you should probably put suitable protection on each SCC input.


Panel spec sheet says 49.9 Voc, temperature coefficient -0.271 %/°C.
"MPPT 250v"
panels wired 4s is good, you'll never get cold enough for 25% rise in voltage.

If PV watts significantly exceed SCC rating, consider orienting some strings SE for morning sun, some SW for afternoon.
Trig and the angle between them will give an estimate of the reduced peak power.

What voltage are the PV breakers rated for? Are they polarized?
Some use two poles rated 150V each to achieve 300V. In that case you could interrupt positive and negative, rather than snaking positive through two poles in series.
I like better to disconnect both ends of the PV string. In my case, the only thing grounding the negative is a 1A fuse. If a positive PV wire shorted to ground, the fuse would blow and suddenly the negative wire I was handling won't be zero volts, it will be 480 volts.

 

[Wits' End]

Thank You for the answers! I'll have a couple more, but I'll ask later ?

 

[Wits' End]

I decided to go with 3@ 2P3S.
I'm going to put 30A fuses in MC4 fuse holders. Located accessibly, at edges of arrays. I'll place those at the start of the 3 @ 8 AWG runs, average <50 feet, to SCC. Unless someone(s) says that 8 over 10 AWG is a total waste.
Breakers before SCC.

Showing an example of my careful planning ?.
My daughter was up laying out the 20x14 & 10x14 white painted areas for enhanced reflectivity. Uh Dad? If we put the arrays like this we won't be able to access the roof. Ok, what if we swap them? That would work. Ok! Flip roof layout over, perfect. And we save a little bit on our cable run ?