Melted fuse holders

[WarmachineX0]

I have these fuse holders, and I've been using them for quite some time. Both on this system for some months now, and on my cabin for years now. I've never had this happen. The fuses are 30a, and I have 15a breakers in each string. The fuses themselves are not burned out and have continuity. The string is 284v 455w, and I have three strings. Two have melted, the third was working fine, but I turned it off. None of the breakers have flipped.

Anyone have any idea what could have caused this? I don't want to just replace them without knowing what caused it.

 

[seneysolar]

Bad connection makes heat. Unfortunately this is pretty common with those.

Get rid of them.

Id go with a Midnite combiner and pv breakers.

 

[WarmachineX0]

Bad connection makes heat. Unfortunately this is pretty common with those.

Get rid of them.

Id go with a Midnite combiner and pv breakers.

Thanks for the reply. I'm already set up there, I use the fuses inline for extra protection. Should I just not be using inline fuses 'at all' if I have breakers or are there anything good for inline?



Edited to add, Looks like a common issue with these.

Mc4 fuse blown

Checked my inverter display this morning and it showed 0 on one of my strings so I got to looking and found a melted mc4 inline fuse holder. I have 2 strings of 6 panels in series. Do these fuses show visible evidence of being blown? The fuse itself appeared ok. Isc for these panels is 10.31...

diysolarforum.com

 

[hwy17]

Thanks for the reply. I'm already set up there, I use the fuses inline for extra protection. Should I just not be using inline fuses 'at all' if I have breakers or are there anything good for inline?

Do you have three or more strings in parallel? If you only have 1 or 2 then no fuses or breakers are necessary.

 

[scrubjaysnest]

Cartridge type fuses are the worst for that type of failure. I use breakers or for fuses MRBF. The MRBF fuse isn't meant for that application.

 

[Brucey]

Thanks for the reply. I'm already set up there, I use the fuses inline for extra protection. Should I just not be using inline fuses 'at all' if I have breakers or are there anything good for inline?



Edited to add, Looks like a common issue with these.

Mc4 fuse blown

Checked my inverter display this morning and it showed 0 on one of my strings so I got to looking and found a melted mc4 inline fuse holder. I have 2 strings of 6 panels in series. Do these fuses show visible evidence of being blown? The fuse itself appeared ok. Isc for these panels is 10.31...

diysolarforum.com

I use midnite pv breakers, no need to add an additional failure point with those in line fuses, safer without them imo.

 

[chrisski]

Can you elaborate?

Bad connection makes heat. Unfortunately this is pretty common with those.

These fuses are quite common especially with branch connectors. Probably hundreds of us on this forum use these to protect parallel strings.

The only thing the OP is doing different is close to 300 volts where most people use less than 100 volts.

Those fuses are 1000 volts rated.

A 30 amp fuse before a 15 amp breaker should not get hot except for

 

[WarmachineX0]

Do you have three or more strings in parallel? If you only have 1 or 2 then no fuses or breakers are necessary.

None in parallel, each string has its own input in my inverters. I'm using two 4865s and run each string to a PV input.

Panels -> isolator and fuse --> rapid shutdown -> 15a breaker -> inverter PV input.

I like emergency equipment at the panels becuase they are so far from everything else.

 

[seneysolar]

Can you elaborate?



These fuses are quite common especially with branch connectors. Probably hundreds of us on this forum use these to protect parallel strings.

The only thing the OP is doing different is close to 300 volts where most people use less than 100 volts.

Those fuses are 1000 volts rated.

A 30 amp fuse before a 15 amp breaker should not get hot except for

Its not a voltage issue or a current overload issue. Its a bad connection causing high resistance and still carrying the rated current.

Like everything there are good ones and bad ones. The bad ones melt down... eventually. I too learned the hard way.

 

[hwy17]

None in parallel, each string has its own input in my inverters. I'm using two 4865s and run each string to a PV input.

Panels -> isolator and fuse --> rapid shutdown -> 15a breaker -> inverter PV input.

I like emergency equipment at the panels becuase they are so far from everything else.

You don't need the fuse or the breaker then. Just the disconnect. So you can definitely get rid of the fuses and leave the breakers if you want.

 

[WarmachineX0]

So after pulling the working one off and examining it, it's worn out. The connections have gotten loose after all these years, the grease has dried up. They weren't like this when I got them, something like 10 years ago. Time or subpar components, I'll need to check the ones on my cabin.

You don't need the fuse or the breaker then. Just the disconnect. So you can definitely get rid of the fuses and leave the breakers if you want.

Thank you. The system is up and charging again, I even removed the working one, didn't want to chance it.

 

[seneysolar]

If anyone needs a inline fuse, get these. On sale right now too!