CONNECTING SOLAR

[gblanchard81]

I have 2 405w panels 9.86a 41.1v pmax 10.37 49.1 isc/voc. So approx 42v 20a coming out. Going to connect them in parallel. Hoping someone can tell me how to wire them from the Y to the mppt... so many conflicting ideas people have... Do I put an inline fuse on each panel(15a) or just after the Y connection(30a) or any at all? Then do I use just a disconnect between that and the mppt or do I use a combiner box with breakers? if so what size breaker?

 

[timselectric]

With less than 3 parallel strings/panels, you aren't required to have any OCP. Although it is recommended that you have a disconnect near the SCC, for convenience and emergencies.
If you want to add fuses, that's perfectly fine. (I always do) put the fuses on each positive, before the Y . Sized according to the sticker on the panels.

 

[gblanchard81]

thanks for the help! what is ocp?

 

[fromport]

thanks for the help! what is ocp?

over current protection

 

[gblanchard81]

Do i need to put a fuse between the scc and the batteries? how do I know which size fuse to use?

 

[mikefitz]

Fuse at battery end of cable to controller. 80 or 100 amps for a 12v system, 40 or 50 amps for a 24 volts system .
Cable must be rated for a higher current than the fuse.
With a MPPT controller the maximum current will be 60 to 70 amps for a12v system, half that for a 24 volts ystem.

Any inline fuse in the panel to controller circuits with two panels will never fail as the panel current is limited. ( although a lightening strike may) . Fuses maybe added as a 'feel good' factor, 15 amps in series with each panel .

Mike

 

[gblanchard81]

Can I use breakers instead of fuses?

 

[mikefitz]

It's a bit impractical to use breakers is series with the panels, inline MC4 fuse holders are the normal.

Low cost breakers are unreliable, need to consider Bussman or similar.

For safety a main fuse should be fitted on or near the battery positive to protect everything connected to the battery. Branch circuits to things like solar controller, inverter, dc distribution fusebox, AC charger, need an individual over current proctive fuse or breaker in addition.

 

[gblanchard81]

Curious... why do I need an 80-100amp fuse from the batteries to the scc, when the scc is only converting 20-25 amps from my panels? How am I supposed to run 2ga from an scc that only takes up to an 8ga... so confused

 

[gblanchard81]

.

 

[timselectric]

Curious... why do I need an 80-100amp fuse from the batteries to the scc, when the scc is only converting 20-25 amps from my panels? How am I supposed to run 2ga from an scc that only takes up to an 8ga... so confused

Size the wire for the amperage and protect it accordingly. OCP can be sized to 125%, to avoid nuisance tripping.

 

[gblanchard81]

Can anyone tell me which wires go to the busbar and which don't? Diagram maybe? I can't find a diagram that actually tells you which wire goes where on the busbar...