Is 2P4S like this doable?

[FilterGuy]

I'm not sure I understand what you are trying to do.

I don't understand either.

 

[FilterGuy]

He's 5 hours behind me.

That's the story of my life..... I am behind on everything! ?

 

[Checkingout]

I'm not sure I understand what you are trying to do.
If you have two groups of 4 panels in different places.
Put one string (top row) in one place. And the other (bottom row)in the other place.

Not in different places, lol, a tiny house roof isn't the size of your roof.
They sit right next to each other, four rows of two, like on the very first photo in this thread.

Given what FilterGuy kindly suggested, I am going to wire each row of four sitting behind each other, in series, and the two rows then in parallel.
This too gives me what I need/want: 100V @15A. So, needs only 14 AWG wire, I have the quality one: 200C silicone.

The question now was basically, if in-series can be such that two halves of the series meet in the center, like so? (ie ignore the red stuff on the left)

 

[Checkingout]

That's the story of my life..... I am behind on everything! ?

No, humor wise even, you are at the forefront of human capacity.
Compare with others ?

 

[timselectric]

If I understand correctly. You want to wire it in two circles (left and right).
And parallel them together in the center.
If I have this right, then yes. That's a good idea.

 

[FilterGuy]

Not in different places, lol, a tiny house roof isn't the size of your roof.
They sit right next to each other, four rows of two, like on the very first photo in this thread.

Given what FilterGuy kindly suggested, I am going to wire each row of four sitting behind each other, in series, and the two rows then in parallel.
This too gives me what I need/want: 100V @15A. So, needs only 14 AWG wire, I have the quality one: 200C silicone.

The question now was basically, if in-series can be such that two halves of the series meet in the center, like so? (ie ignore the red stuff on the left)

View attachment 183825

Is the sugestion to tie the two center points together like this?

I can't think of how that would improve anything but I can imagine that there are scenarios where that would perform worse.
In addition, I think that probably creates a safety issue where a short in a panel would have to take more current than it can handle without a fire hazard.

 

[MisterSandals]

Maybe this will help if you want to wire from one end. Panels will need to be close together but most have leads long enough to do this.

Sorry for the ugly graphic.

 

[timselectric]

I can't do any diagram. But I don't think they want to change the 4s2p.
They just want to rearrange the physical configuration. To use less wiring.
The 4 panels on the left as a string.
The 4 panels on the right as a string.
Top center as main negative.
Bottom center as main positive.

 

[Checkingout]

Is the sugestion to tie the two center points together like this? - No, not like that, I cannot even understand why one would do that?
View attachment 183830
I can't think of how that would improve anything but I can imagine that there are scenarios where that would perform worse.
In addition, I think that probably creates a safety issue where a short in a panel would have to take more current than it can handle without a fire hazard.

Maybe this will help if you want to wire from one end. Panels will need to be close together but most have leads long enough to do this.

Sorry for the ugly graphic.

View attachment 183856

Hmm, this too I don't even understand. (sometimes I have been wondering if I am developing Alzheimers... but a woman with an Alzheimer aunt in her family said: "No, you would be very different!" okay then).


Well, after FilterGuy's suggested connection of the 8 roof panels, since I need the final + and - wires to come down the house almost in the center of the 4-in-series-string, I was initially wondering if it's wise, or okay, to wire 2-in-series, and the other 2-in-series, and then combine those 2 sets of 2 as a new in-series connection. A kind-of nested in-series connection, if that makes sense. It would require 2 additional Y connectors but less wiring (not having to come back from the left after just going there with the wiring).

Meanwhile however I feel like that was a foolish thought of mine. But I will shoot a photo outside later to benefit understanding (cannot go out now as the phone is bluetoothing a video clip to the desktop, which feel like it'll take forever if it looses connection I have to start all over again)

 

[Hedges]

When you do skip wiring between panels, easier to mix things up.

Check voltage and polarity before making final connection to inverter or SCC. (be careful not to touch exposed DMM test leads when one is plugged into MC4 connector.) Also before paralleling the two strings, or plugging into anything where you can't see the other end. My meter typically reads Voc for a moment, decaying to zero as capacitance of open-circuit wire charges up. If not, current is going to flow when connected.

I have done similar wiring to minimize the extension PV wires needed.

 

[MisterSandals]

since I need the final + and - wires to come down the house almost in the center of the 4-in-series-string,

Then maybe something like this for 4S. Do this twice and connect the 2 strings in parallel anywhere that is convenient.

 

[timselectric]

I don't have fancy computer skills. But, this is what I described, earlier.
I believe this is what you want to do.

 

[Checkingout]

When you do skip wiring between panels, easier to mix things up.

Check voltage and polarity before making final connection to inverter or SCC. (be careful not to touch exposed DMM test leads when one is plugged into MC4 connector.) Also before paralleling the two strings, or plugging into anything where you can't see the other end. My meter typically reads Voc for a moment, decaying to zero as capacitance of open-circuit wire charges up. If not, current is going to flow when connected.

I have done similar wiring to minimize the extension PV wires needed.

Very important points, yes! Thanks. 100V is not for the faint-hearted, I've seen in videos that much lower voltage can kill you.
What I thought is, once I have all necessary items (missing still):
- just before darkness, connecting P1 to P4 in-series, and P5 to P8 in-series
- because of low light though, you cannot check now if voltage increased as expected, and if amperage is okay still (next day then)
- and then connecting series-1 to series-2 in-parallel. It is here where I will increase wire size from AWG 14 to AWG 10 leading the wire down the house, into the basement, and back up the small bit to where the utility box is awaiting the roof panel power.
- Again, from where I combine both 100V 7.5A in-series strings, in-parallel to 100V 15A, I will use the thicker wiring through to the end, the Charge Controller (CC).
- Since it's "dark" by then, I assume it should be safe to make the connections. And any measurement in "darkness" wouldn't yield much above 0 anyway, is my thinking. Measurement would have to be next day, by checking of the CC puts anything out? If not, then comes the "fun" part: measuring in full sun

As promised, here a photo of the roof panel arrangement. Not as big as Tim's, be aware:



By the way, the low winter sun is the reason why I spread out the panels to this exact distance, it's all measured based on known sun's altitudes.

The particular constellation (I like the word here ) gave me rise to consider if the in-series strings should be comprising different panels, than what I understood FilterGuy suggested:




Anyway, here FIY, if you are interested? This is how I've been angling all panels for the past 10ys, the rear wall panels use the same easy mechanism. On the roof, obviously, I will only make one change between low winter sun, and high summer sun:




Given it's now about roof wiring (strong sun here in summer!), I am still contemplating how I pin down the wiring:
- if you pin wiring straight onto the metal roof, it heats up needlessly (the roof is so hot in summer, I cannot step up! My wiring is silicone 200C though, so, it won't burn through from this). But still, you don't want to heat up your wiring from the outside even. No.
- but if you don't pin down the wiring, you end up with loose wiring bouncing around (and at times touching the hot roof nonetheless!).



So, yeah, this is sth I am still contemplating what I would like most...

Then maybe something like this for 4S. Do this twice and connect the 2 strings in parallel anywhere that is convenient.

View attachment 183936

Yes exactly! Though I think it's what FilterGuy meant as well?