Combining PV from separate roofs and medium/high voltage DC runs between buildings

[totalconfusion]

I’ve got a house and a shed that are getting panels fitted. The distance between them is 20m. The house will have 8 panels and the shed will have 4.

The battery/generator room is located in the shed. I plan to have the breakers in this room.

I plan to run a split set up 4s2p (house roof) + 4s1p (shed roof) both terminating in the battery/generator room in the shed.

Panel specs:

x12 Trina TSM-415DE09R.05
Panel wattage = 415w
Open circuit voltage (Voc) = 50
Short circuit current (Isc) = 10.55

Apologies if I throw the term combiner box around pretty loosely, Any box with a combination of fuses, SPD’s and circuit breakers is a combiner box in my head.

I have a few questions mostly regarding combiner boxes and safe distribution of medium/high voltage DC (240vdc)

I was under the impression I should be using a total of 3 “combiner boxes”

1. On the house roof where two PV strings will terminate in to a total of four fuses (both positive and negative)
2. On the shed roof where one PV string will terminate in to a total of two fuses (both positive and negative)
3. Inside the battery/generator room there will be a box that has a 4P circuit breaker that will take the two separate PV inputs.

Where should the SPD(s) go? On the rooftop boxes or in the same box as the circuit breaker? What type of SPD?

How should I be connecting the two separate PV inputs into the circuit breaker? Ferrules and a bus bar connecting the MCB inputs?

Is it dangerous to be running 240vdc in conduit for 20m at ground level? What considerations should I be thinking about?

Is it okay to use the 50A 4P MCB as a PV isolator? And is the MCB rated correctly at 50A?

My best guess at how panel frame grounding should be done is in the diagram, how wrong is it?

I’m looking at some SJBeny combiner boxes and the quality looks pretty decent for the price. What are the differences between these two models? One’s fused and rated for 1000v whereas the other is unfused and rated to 600v? Could I get away using a the 32amp combiner where I've calculated 33A? I used a 1.56x safety multiplier on the max PV Isc calculations



OR



I’m thinking of a 2 string box on the house roof and a 1 string box on the shed roof. It’s just the location of the fuses and SPD’s that’s throwing me.

Can I just combine and surge protect on the roof then fuse and circuit break on the ground?

Sorry the million questions :/

Thanks!

 

[totalconfusion]

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