Should I fuse the positive wire from the solar panel to the charge controller?

[Joanna]

I am getting conflicting information and I am not sure what to do. I have a 400W Solaria PowerXT-400R-PM Monocrystalline Solar Panel. According to Nate at Explorist Life, I do not need a breaker on the positive wire coming from the solar panel. His argument seems sound. But the wiring diagram I got from Light Harvest Solar has a 30A fuse on the positive between the solar panel and the charge controller. I just don't know who to listen to!! I am leaning in favor of what Nate says, but I wish I understood the issue better so I could feel confident in my choice.

 

[Bud Martin]

Is this the exact panel you have?

https://static1.squarespace.com/static/5fa44724b1ca66220ca21c60/t/60a44f1fb82d4c0854de640f/1621380896438/Datasheet_PowerXT_Resi-400PM_AU.pdf

It suggests to use fuse up to 20A max. It is good to have DIN fuse holder or circuit breaker so you can use it as a disconnect.

 

[rmaddy]

You don't need to fuse a single panel. It's only once you get 3 or more strings in parallel that you need to fuse each string.

But it is common to have a disconnect breaker near the SCC so you can disconnect the solar panels easily if needed. I believe Nate has a whole discussion/video on the disconnect breaker.

 

[Joanna]

Is this the exact panel you have?

https://static1.squarespace.com/static/5fa44724b1ca66220ca21c60/t/60a44f1fb82d4c0854de640f/1621380896438/Datasheet_PowerXT_Resi-400PM_AU.pdf

It suggests to use fuse up to 20A max. It is good to have DIN fuse holder or circuit breaker so you can use it as a disconnect.

Yes - that is the exact panel. I do have a solar isolator to use as a disconnect. The argument against a fuse/breaker is: Solar arrays having higher current availability (parallel strings of solar panels) than the maximum overcurrent protective device rating specified for the panel shall be protected from overcurrent. EXCEPT when the short circuit currents from all sources do not exceed the ampacity of the wires and maximum overcurrent protective device size rating specified on the PV module nameplate.

In this case, the short circuit of the panel (9.82A) does not exceed the max series fuse rating of the panel (20A).

 

[Bud Martin]

You only have one panel and since you already have the disconnector so really no need for the fuse then.