PV cable and fuse size

[withaview2]

Hi, everybody!

Trying to get the ball rolling with the PV set-up and would appreciate some help choosing correct cable size and fuses between panels and SCC.

Set-up is as follows.

3x375W (1125W) in series at 24V.

Array will be stationed max 30ft from SCC/inverter and batterybank.

Some specs.

PV

Output cable: 4mm2.
Max fuse rating: 20A.
Vmp: 34.6(stc) 32(noct)
Voc: 41.1(stc) 38.4(noct)

Possible SCC (EPever UP3000-HM10022)

Input voltage: 24V
Max battery charging current: 100A
Continuous output: 3000W
MAX PV charging current: 100A
Max PV charging power: 2750W
Max PV open circuit Voltage: 500V
MPPT Voltage range: 80-350W

The UP-Hi manual recommends 6mm2/9AWG PV wire size and 2P40A breaker. Output cable on PV is 4mm2/12AWG.

Now to the questions, bear with me please.

Are fuses necessary between the PV and breaker, or will the breaker be enough safety? If not, should they be the same as the max fuse rating of the PV, or max current power of PV?

Also. Is it a big NO to mix cable size in between panels and/or between panels and SCC? The reason I'm asking is because I already got two 13ft 12AWG MC4:s I would like to use somehow. And perhaps two 3ft 9AWG between panels.

I'm a bit confused by all the variables and numbers and would be thankful for help.

 

[mikefitz]

No fuse needed on a single string between panel and controller. Providing the MC4 connectors match, no problem mixing cable size.
Power loss at full power due to cable, assuming all the run is one size, 4mm2 10 watts, 6mm2 6 watts.
A double pole DC isolator rated for the panel volts and current between panel and controller.

Mike

 

[withaview2]

No fuse needed on a single string between panel and controller. Providing the MC4 connectors match, no problem mixing cable size.
Power loss at full power due to cable, assuming all the run is one size, 4mm2 10 watts, 6mm2 6 watts.
A double pole DC isolator rated for the panel volts and current between panel and controller.

Mike

Thanks. That's exactly the response I was hoping for

A 2P 20A breaker. 4mm2 run between PV:s and SCC and 6mm2 connecting panels. If need be I can always upgrade later.

 

[OnGrid]

Are you putting your panels on your roof?

 

[withaview2]

Are you putting your panels on your roof?

No. The plan is a ground mount.