Awkward PV wiring question

[tonyg]

Hi,

There will be some panels mounted further away from the MPPT and inverter, about 20m away.

The panel configuration is 3s3p (3 series, 3 parallel). Each panel is 41.2V VoC and 12.28A Isc. That means over 30A when all are combined.
Victron says MC4 connections are rated to 30 A only, and as such, I plan to bring all the wires for each of the series (6 wires in total) to the shed, where I'll combine them appropriately and do the surge protection, etc.

I think this is better than combining the output at the panels' place (hard to access rooftop) and then bringing just two thicker wires to the shed, right?

Many thanks.

 

[Supervstech]

Hi,

There will be some panels mounted further away from the MPPT and inverter, about 20m away.

The panel configuration is 3s3p (3 series, 3 parallel). Each panel is 41.2V VoC and 12.28A Isc. That means over 30A when all are combined.
Victron says MC4 connections are rated to 30 A only, and as such, I plan to bring all the wires for each of the series (6 wires in total) to the shed, where I'll combine them appropriately and do the surge protection, etc.

I think this is better than combining the output at the panels' place (hard to access rooftop) and then bringing just two thicker wires to the shed, right?

Many thanks.

I am a fan of simple. If it is easier for you to use 6 sets of #10 or 12, than it is to use a single pair of #6 that is your decision. Keep in mind, conduit size choice is worse when more than 2 wires are used in conduit. Code requires 40% fill max, and conductor derating iirc…

Derating Current-Carrying Conductors for Conditions of Use | JADE Learning

If you ask a seasoned electrician how many No. 12 AWG conductors will fit into a 3/4" EMT conduit system, you may get a response such as “one more!” While this is amusing (and typically true), there are precautions that must be taken according to the NEC whenever conductors are bundled together...

www.jadelearning.com

 

[timselectric]

Slocable Solar Panel Connector 1500V 1000V IP68 Waterproof 50A PV Plug Tinned Copper Pins 5 Pairs (10mm2 (8AWG)) https://www.amazon.com/dp/B08CN4Y49V/ref=cm_sw_r_cp_apan_i_C857DN2D7NM0XT28YXTD

 

[DThames]

I would guess you need to bring the wires down from the roof to the ground, before exiting the shed location. If you combined at the shed, but not on the roof then you would have easy access to the connections if you wanted to disconnect a string for testing or whatever. With the cost of wire, I would work to avoid 6 conductor 20m run, unless the wire cost was a wash. Second thought, smaller wire is easier to pull. I have 6, #10 THHN in a 1" conduit, pretty easily.

 

[TomC4306]

I think this is better than combining the output at the panels' place (hard to access rooftop) and then bringing just two thicker wires to the shed, right?

Only you know the situation best .
I agree with your conclusion.