PV Inline Fuse for 2P

[HLD]

I've got a 6S2P array with 12 445w Panels. The panels have an ISC of over 10a and a maximum series fuse of 20a. I've seen several people on this forum say you don't need an inline fuse with 2P but i'm not sure why.

Why would 2P not require an inline fuse? Does it have something to do with the way the current can travel between those strings?

If I did add inline fuses on the positive lines for both strings would it give me loss or simply no protection at all? Is there a reason I wouldn't want to do that?

*By inline fuse i'm referring to the type that are labeled as MC4 fuse holders with a 20a fuse in them them, positioned just before the branch connection on the two strings.

 

[sunshine_eggo]

In single strings or two in parallel, panels are self-fusing below the wire rating, i.e., if there's a short, one of the panels will fail and open the circuit protecting the wires.

At 3P the panels can handle more current than the wire, so the wire is at risk.

No harm or downside to putting one MC4 fuse in each string.

 

[HLD]

In single strings or two in parallel, panels are self-fusing below the wire rating, i.e., if there's a short, one of the panels will fail and open the circuit protecting the wires.

When this occurs is the panel permanently damaged?

At 3P the panels can handle more current than the wire, so the wire is at risk.

Would this be true regardless of string size?

 

[sunshine_eggo]

When this occurs is the panel permanently damaged?

Yes. Fuses and breakers are about protecting wires and preventing fires. Equipment isn't a concern.

Would this be true regardless of string size?

A 1S, 2S or 10S string of the same wattage panel always have the same current. The higher string voltage just mandates that the fuses/breakers be rated for both the current and voltage.