Wiring Panels in Series-Parallel | Is this diagram correct?

[AZ Off-Gridder]

Here is my 48V solar system.

Inverter: MPP LV6048 6kW
2 PV inputs in this unit. 4,000w max per input. Max PV input 145vdc each input. MPPT range 60-110vdc. Max solar charging current 80a per input.

Solar panels: (18) 250w VPM 30.3v. Max power current 8.27a

Planning to wire these panels in 2 separate sets of 9 wired as S3P3. Below is a diagram of only one half. There would be one more identical to it as 4,5,6. Each set would feed the inverter separately. (As this inverter is technically 2 inverters side by side.)

Wiring: As shown in the diagram, wired into a series string of 3 panels, and then 3 strings paralleled. @ 90.9v and 24.81a. I plan to use MC4 3 to 1 pigtails to connect into parallels.

Questions: Does this make sense?
Am I wiring them correctly?
Will it function safely within the inverters parameters?

MUCH THANKS to the community!!!

 

[acdoctor]

Yes it is correct for 3S3P however each series string needs fused or breakers. A way of disconnecting them is a good idea as well. And don’t forget surge device also. A combiner box would be great.

 

[AZ Off-Gridder]

Yes it is correct for 3S3P however each series string needs fused or breakers. A way of disconnecting them is a good idea as well. And don’t forget surge device also. A combiner box would be great.

What one could you recommend for this scenario?

 

[MisterSandals]

What one could you recommend for this scenario?

Other than a combiner box, you could do what you want with 2 pair of these:

https://www.amazon.com/POWISER-Connectors-Branch-Parallel-Adapter/dp/B08K93CQZQ/

And 6 (was thinking 2 when i originally wrote this) of these (sized 150% of Isc of your strings):

https://www.amazon.com/Renogy-10-Waterproof-Line-Holder/dp/B00YG1DY20/

 

[AZ Off-Gridder]

Other than a combiner box, you could do what you want with 2 pair of these:

https://www.amazon.com/POWISER-Connectors-Branch-Parallel-Adapter/dp/B08K93CQZQ/

And 6 (was thinking 2 when i originally wrote this) of these (sized 150% of Isc of your strings):

https://www.amazon.com/Renogy-10-Waterproof-Line-Holder/dp/B00YG1DY20/

Great links thanks! The 3 to 1 Seems simple and cheap. So what’s the big catch? What reasons should I NOT take the easy way? Why is a combiner box better? Or is it all just preference? Thanks!

 

[MisterSandals]

Why is a combiner box better? Or is it all just preference? Thanks!

I didn't want a combiner box on my RV roof. I only needed 2-way Y cables.

It theory you should fuse your panels/strings when combining 3 or more in parallel. The reason is that if it backfields the amps from 2 panels, it is more than the panel can likely handle (see max fused amps on panel back). You have quite a few panels so you really should add the fuses to each 3S string... guessing on the positive end, just before the 3:1 combiner.

Most of these connectors are made to handle 30A, like the 10AWG wire they protect.

 

[AZ Off-Gridder]

I didn't want a combiner box on my RV roof. I only needed 2-way Y cables.

It theory you should fuse your panels/strings when combining 3 or more in parallel. The reason is that if it backfields the amps from 2 panels, it is more than the panel can likely handle (see max fused amps on panel back). You have quite a few panels so you really should add the fuses to each 3S string... guessing on the positive end, just before the 3:1 combiner.

Most of these connectors are made to handle 30A, like the 10AWG wire they protect.

My panels say 15amp max fused

 

[MisterSandals]

My panels say 15amp max fused

I'd use 15A fuses then (or whatever is 150% of your string amps, if significantly lower).

15A is very common for max fused amps.

 

[AZ Off-Gridder]

(or whatever is 150% of your string amps, if significantly lower)

Is my string amps 8.27? Or 24.81? Thanks

 

[MisterSandals]

Is my string amps 8.27? Or 24.81? Thanks

3 panels in series has a max (short circuit) amperage of a single panel amperage (Isc). And voltage is 3x Vmp (working voltage).

I do not know your panel specs...

 

[Bud Martin]

Is that the spec of the panel Isc?
Each string is 8.27A (8.27A x 3 = 24.81A), so at 150% the fuse will be 12.4A, you can use 12A fuse for each string will be fine.

 

[MisterSandals]

you can use 12A fuse for each string will be fine.

Yes but much much harder to find in MC4 inline fuse form. (only 10A, 15A, 20A, 30A from what i've seen/found).
I would opt for 15A if using inline variety from link above. Everything is rated at 15A or above, including 10AWG and connectors rated at 30A.

 

[AZ Off-Gridder]

Yes but much much harder to find in MC4 inline fuse form. (only 10A, 15A, 20A, 30A from what i've seen/found).
I would opt for 15A if using inline variety from link above. Everything is rated at 15A or above, including 10AWG and connectors rated at 30A.

Perfect thanks for the help. Now while speaking about wire AWG I’d like to ask. My panel array is planned to be 130 feet from my inverter. And all the MC4 wiring that will connect the panels is 10awg standard. What AWG is necessary to reach my inverter without crazy loss? Or maybe I should ask what amount of loss can I expect if 10 AWG is used to travel 130 feet? Many thanks!

 

[Bud Martin]

Yes but much much harder to find in MC4 inline fuse form. (only 10A, 15A, 20A, 30A from what i've seen/found).
I would opt for 15A if using inline variety from link above. Everything is rated at 15A or above, including 10AWG and connectors rated at 30A.

That is true, 15A is more common. I got mine from Aliexpress a long time ago.:

0.93US $ 15% OFF|Solar In-line Fuse Connector 1000v Dc Male To Female Pv Solar Fuse Holder Protection 2/3/5/10/12/15/20a /30a/32a - Connectors - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[MisterSandals]

if 10 AWG is used to travel 130 feet?

Barely acceptable at 2.88%. Need to check ampacity of your wire though.

 

[WYtreasure]

Perfect thanks for the help. Now while speaking about wire AWG I’d like to ask. My panel array is planned to be 130 feet from my inverter. And all the MC4 wiring that will connect the panels is 10awg standard. What AWG is necessary to reach my inverter without crazy loss? Or maybe I should ask what amount of loss can I expect if 10 AWG is used to travel 130 feet? Many thanks!

https://solarwiresizecalculator.com/

 

[MisterSandals]

Actually i got that wrong, i did not consider combining the 3S strings to make 25A after the combiner.

You REALLY should look at making your array a higher voltage (more panels in series) to get the volts up and the amps down.
What is max input voltage of your SCC?

 

[AZ Off-Gridder]

What is max input voltage of your SCC?

145vdc PER SIDE so technically 290vdc total. Because it’s two inverters in one unit

 

[WYtreasure]

I will be tying my strings together within a NidNite Solar MNPV6 Combiner Box. Should help quite a bit with staying "neat & tidy".

And as MisterSandals suggests, up the voltage (watch out for the super cold temps) as much as possible for the long run to minimize loss.
No reason to start tossing your hard earned power down the crapper before it even gets to your place.

 

[AZ Off-Gridder]

And as MisterSandals suggests, up the voltage (watch out for the super cold temps) as much as possible for the long run to minimize loss.

That was my initial thought. But in another post I was cautioned against high-voltage DC due to safety reasons… I’m open to anything I just want a solid system that works, lasts, and is safe. And as far as temps go it’s Arizona Desert valley at around 2,200ft so annual highs are 105f and lows maybe 45f for daytime temps.