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Looking for advice on PV fuses

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I hope someone can help.

I have a solar installation comprising 3x3 Canadian 360w panels, 5kva hybrid inverter and 2x4.8 Li batteries.

I have noticed that the fuses in line from the panels and the isolator are rated 30A. The isolator is an AC switch. The fuses and the isolator get so hot the the container has started to melt. I called the installer and he replaces the fuse holders and isolator like for like. This has not solved the problem.

I read on an overseas site that there is a formula for determining the required fuse rating. Fuse rating = (short circuit current x 1.56) / temperature coefficient. When I apply this formula I get a result of 50A. The s/c current for each panel is 9.5A. Three in series should be about 30A. The temperature coefficient for the place where the panels are mounted is 0.95.

I would like to know if this method of determining the fuse rating is correct for this type of installation.


Thank you very much.

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  • 10 months later...
2 hours ago, LukaX7 said:

Hi There, 


Did you manage to resolve as I have the same problem

Yes I did. The original installation, performed by a "professional" installer grouped the three strings of panels into one on the roof. He then used a similar sized cable to connect to the fuse box with only one fuse in it. the cable from the roof was under rated for the current it was carrying. I resolved this by running two additional cable pairs from the roof to the fuse box so each string was on it's own circuit to the fuse box. I added two more fuse holders and fuses on which the strings terminated. The three strings only came together at the isolator switch. So each string carried about 10A. I used 15A fuses. Result is no heat or melted switches. I'm sure if I had not done this I would have had a fire.

I hope that this helps you.

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