Looking for wiring tips

[LeeLewis]

The image is a simple representation of the setup.
The panels are on a canopy that is around 40 feet from the house.
Wiring the strings will be done on the canopy then I would bring the final output into the house and a panel.
The question is, what's the best way of doing this since going from the canopy to the house will be around 75 feet and the wire gauge needed will make it very expensive.
If I used the smaller wire from each string to the house, it would end up being hundreds of feet of 12 gauge or so and a large bundle since there are in fact around 40 panels. Using heavier gauge from the combiner box to the house seems to be about the only option but wondered if you had some thoughts on this.
It would be difficult to have batteries outside as well.

UPDATE: I provide more information about the panels in a further comment below.
I also updated this diagram because I keep making mistakes using the drawing tool.
This diagram is showing just one string connected but the combiner allows up to six.


solar-parallel.png

[SunEagle]

I guess my question is how many DC amps are you running from the combiner box to the inverter? That would help with the voltage drop calculation for the wire size.

Sometimes it is less costly to run AC a long distance then DC so maybe having the inverter closer to the combiner box may be less expensive in wire costs since it is AC and not DC.

[LeeLewis]

Thanks for responding.
The current setup is grid tied, with 4 string, 2 x 10 and 2 x 11 panels.

Since each panel can output a max of 0.992A, even if I connected all 40, I'd be in the 40A range max.

However, I would not be connecting all 40 panels, probably only 10 to start so would use a combiner that has four 15A inputs with a 50A output breaker.
I would use one of the string inputs on this device; https://www.amazon.com/dp/B09BTX2YQ5

I considered putting the inverter outside on the canopy but it would have to be weatherproof or I'd have to build a weatherproof cabinet for all of the equipment.
That said, I expect there will be a lot more hardware than just the inverter which is why I'd like to get the combiner output into the house and then onto a large board mounted to the wall due to difficult access in the area of the canopy.

The two issues are that everything around the canopy is very difficult because it's on a steep hill and second, there's an HOA that dislikes solar so am trying tobe as inconspicuous as possible.

[bcroe]

I do not know what panels you are using, but for long runs best
efficiency will be at the highest voltage practical. Here 12 250W
panels in series give about 400VDC operation, 500V open circuit.
This runs a 400ft loop at around 1% loss max. If your panel array
runs higher voltage than your inverter output, best make the DC
the longest part of the runs. Look up wiring resistance and figure
out operational losses.

One way to save on expensive copper, is to use aluminum, up
it 2 gauges larger for the same losses. Here aluminum Triplex
for $650 replaces copper for $2700. Triplex direct burial also
eliminated a need for underground conduit, but required a depth
of 24 inches instead of conduit at 18 inches. Aluminum requires
terminations designed for it, best coated with oxide preventing
OX-GARD. good luck, Bruce Roe

[LeeLewis]

Thanks for the input.

The panels are Mage / Powetec Plus, 250 / 6 PL US AC.
AC Max Cont output current, 0.992A
AC Max Cont output power, 238W

The inverters being removed are Pantheon II.
INPUT (DC) DATA P250LV-208/240
Recommended STC Module Input Power Rating 235 W – 280 W
Maximum Continuous Input Power 250 W
Maximum Input Voltage 48V
MPPT Voltage Range 18V-37V
Maximum Power Voltage Range 25V-37V
Maximum DC Short Circuit Current 15A
Maximum Input Current 10A

The panels will be used without the inverters.
There is no electrical information about these panels other than with the inputs of the inverters which is how I came up with these numbers.

However, the math doesn't add up so I'm not 100% sure what each panel outputs.

Given 238 watts and up to 48 volts DC...
Amps = 238 watts / 48 volts
Amps = 4.9583 amps (rounded to four decimal places)
Therefore, with 238 watts and a maximum voltage of 48VDC, would give approximately 4.9583 amps.

I have the option to go with series or parallel too since I've not purchased any inverter yet. I do have shading issues so am preferring parallel.

[bcroe]

It appears to me, that .9A figure is the 240VAC output of a micro inverter
attached to the panel. Since you are connecting all the panels DC outputs
together at a combiner and then to the inverter (no micro inverters), you
might see individual panel DC outputs something like 32VDC at 8ADC.
Bruce Roe

[LeeLewis]

You're right as I think about it because the .9 amps mentioned in the data sheet is talking about the inverter output, and at 240VAC.

I measured the average voltage of the panels and it was in the 32VDC range. I did not test the current however as I thought the information I had was giving me what I needed.
That throws everything I thought into the garbage bin. At 8 amps per panel, even the combiner I already bought is too small to form 3 panel strings as it's inputs are fused at 15 amps.

To safely use this combiner, I would not even be able to string two panels. That doesn't seem to make sense. I've seen people stringing up to 10 panels to one input of these combiners so I'm rather confused now.

Let's see if I can figure this out.

The data sheet only talks about the inverter output since the panels come with the inverters mounted.
So, we're talking about the AC output when connected to the inverter, being 0.992A at 240VAC.
Inverters are maybe 95% high efficiency, we can estimate the DC input power to the inverter by multiplying the AC output power by the inverter efficiency.

DC input power ≈ 0.992A * 240VAC / 0.95 ≈ 250W

Since the average input voltage to the inverter from the solar panel is around 32VDC, I can estimate the DC amperage output per panel.

Using the estimation of 250W for the DC input power and an average input voltage of 32VDC, we can calculate:
DC amperage output per panel ≈ 250W / 32VDC ≈ 7.81A

Close to what you're saying but still nowhere near what I was thinking. I don't think I even saw any combiners that have more than 15 amp inputs.
Does it mean I'd be limited to one panel per input or maybe taking a chance with two, being too close to the fuse rating.

[bcroe]

Lots of combiners expect you to put an 8A panel string on each of
the fuse positions you mount. The fuse can act as a switch, except
do not open it under any current. I use a dual channel combiner
for near 50A total. Bruce Roe
CombAug18.JPG

[LeeLewis]

Maybe I'm not explaining correctly as I don't know all the terminology.
I read that sometimes, a string might mean one panel and another time, a string means multiple panels connected together in series or in parallel.

I bought this combiner; https://www.amazon.com/PowGrow-Combi...dp/B09BT91PHN/

My thought was to connect three panels in parallel per input and there are four. Because I thought the panels, strung together would be around 3 amps, those inputs were more than enough.
Now that we're saying each panel might carry 7-9 amps, I could only be able to connect one panel per input so a total of four panels into this combiner.
Or, I could push it a little and connect two panels in series per input and with the shading I get, might never hit the 15 amp fuse limit per input.

[bcroe]

You can connect up to 4 series STRINGS of panels, each might run 8-10A,
15A fuse. Bruce Roe

[LeeLewis]

I'm sorry, there is something I am obviously not understanding.

I thought we said that each panel could put out between 7-9 amps. The combiner has four 15 amp inputs and one 50 amp output breaker.

[SunEagle]

I'm sorry, there is something I am obviously not understanding.

I thought we said that each panel could put out between 7-9 amps. The combiner has four 15 amp inputs and one 50 amp output breaker.

When panels are wired in series then your voltage is added up and increases but the amp total is the average of the panels. So with 4 panels of the same amperage (say 7-9 A each) the total amps of those 4 wired in series is still only (7-9 amps).

[LeeLewis]

Ah, yes, I'm following now. It's because I mentioned I don't already have an inverter so my choices are flexible.

For example, if the voltages of four panels are as follows: 18VDC, 25VDC, 30VDC, and 37VDC, the total voltage when wired in series would be:
18VDC + 25VDC + 30VDC + 37VDC = 110VDC

The only concern is shading issues but maybe I have to take what I can get. That's why I wanted to do strings of three panels.
I suppose inverters are able to handle fluctuations of input voltage while still being able to convert that to usable battery charging or even charging and AC.
I have to look into inverters or solar charge controllers now I suppose.

[DanS26]

Your diagram shows the Daisy chain method......but you might want to look into using the Leapfrog method for wiring up the panels.........

https://www.winaico.com.au/solar-wiring-techniques

[LeeLewis]

Oh, I accidentally drew that after I messed up my first try. I'll update that to show it being parallel. I'd like to have strings of 3 panels because of the way the canopy is installed. That would be the best method for me in terms of shade problems. I'll update that and upload it as soon as I can.