Negative Wire extremely hot

[SteveP]

Hi All.

Relative newbie here. I put in panels about 3 months ago. Today I noticed the negative wire fron the panels had gotten so hot it had melted the screw clamp connection at the charge controller. What would cause this?

Thanks!

[SunEagle]

Hi All.

Relative newbie here. I put in panels about 3 months ago. Today I noticed the negative wire fron the panels had gotten so hot it had melted the screw clamp connection at the charge controller. What would cause this?

Thanks!

Welcome to Solar Panel Talk Steve.

It would be hard to come up with a reason until we know more about your system and how it is wired.

I would hazard a guess that the wire is "common" to more than one panel and that it may be too small to carry the return current for multiple panels. But I am jumping ahead without really knowing how your system is put together. Give us the panel specs, wire size, charge controller data along with how it is all wired together along with any fusing that is used.

[SteveP]

You just confirmed my suspicion on the small wire size.

Thanks!

[Sunking]

Loose connection or undersized wire. Since it is only one polarity, loose connection would be my guess because both would be hot if undersized. If the wire it is only warm near the connection and not the whole length or wire, it is a connection error.

With that said did you do the voltage drop calculations to fin dout what size wire it would take to keep at 2 % loss or less? I did not think so. Time to do that and it will require you to re-wire it once you discover how much power you are loosing.