DC fuse caught fire! Help ?

[BradCagle]

Hi All!

So I'm kinda new , I have 8 panels 320V ( 3.1kw ) in series open circuit voltage and a AIO 3.6kw inverter.

So I got these DC fuses to install between the panels and the inverter.

I checked with the multimeter that the polarity was good and when I closed both + - circuit fuses I was reading 0v and then when I tried again one of the caught fire!

I read about the current flow that it has to enter in a specific way for DC breakers but mine is just a fuse and it doesnt mention current flow diagram ? Or I don't understand.

Should have I connected the panels on top of the fuse ? Or is something else is happening ?

I tried to turn on the inverter with just battery and it works fine it seems. Is there any possibility I have destroyed something in the panels or the inverter ?

Thank you!

Edit : The housing is made in france and the fuse made in italy. Shall I get a circuit switch breaker instead of fuse ? Im going to the shop again to buy new
View attachment 114362View attachment 114361

I tried fuses, and housing similar to what you have. Mine got scary hot, and when I started smelling plastic melting I shut it down.

I switched to midnight breakers. I wont do the fuses ever again.

 

[Hedges]

I tried fuses, and housing similar to what you have. Mine got scary hot, and when I started smelling plastic melting I shut it down.

I switched to midnight breakers. I wont do the fuses ever again.

Just carrying current, not arc on closing?
Any chance it was wire to terminal, or do you think it was clip contact to fuse?
What fraction of rated current?

I had a box full, but carrying 7A through 15A fuse in each 30A holder.
Power dissipated proportional to I^2R, so 1/4 rated self-heating of fuse, 1/16 rating for fuse holder. very benign.

OP's 12A fuse in 32A holder, with ~ 10A to 12A panel, could have made fuse hot (normal rated temperature) but holder should have been fine.

 

[EliteSolar]

The fuse itself is good for the voltage of your PV array, and probably won't blow with the current.
(I think 12A fuse is smaller than the recommended minimum 1.56 x Isc; what are ratings on PV panel label?)

The fuse holder is touch-safe, but not meant to open or close with load.
If closing the fuse holder shorts the PV string, then fuse to fuse holder contacts would burn under load.
If wire connection isn't good, that would heat up.

If PV string is wired reverse-polarity, it hopefully has protection diode, but that makes a short circuit.

You should check voltage across fuse holder with DMM before closing. If that completes circuit to inverter, capacitor would take forever to charge up through 10 meg ohm DMM, looks like a short. In that case, a precharge resistor scheme might be advisable. I have fuse and switch. DMM briefly shows voltage across switch just charging capacitance of wire. I check polarity with DMM, then close switch.

Hi , as I said my LSC is 11.07A and LMP 10.57 and my fuse is 12amp , I know not ideal, but doesnt explain the problems I have, does it ? I am not having any load on the AC output , I just want to power the inverter for start.

So what you say , that if the fuse holder shorts the PV string , that explains why it didnt burn last night at sunset, it was quite dark ( I had like 250V ? instead of 330V ~ ) and the voltage drop stayed at 0, as I explained before , but burnt today when there was full sun ( it was around 330V I think when it burnt ) ?

I checked with the multimeter that my positive and negative are correct.

I tried to find switches but DC not available. So the only way to close the circuit is to close the fuse , or connect the mc4 cables ( or connect directly to inverter ( I would never do that for safety reasons ) .

When I closed both fuses voltage dropped to zero before or after the fuse. 2nd time I tried it after I checked all my cables , one fuse holder caught on fire .

So the problem really is why is the inverter shorting the PV array ?

Thank you all for your responses I highly appreciate it because I can't get anyone near me to help me with my setup. And I also love to learn new things ( without dying hopefully )

 

[Danke]

You need to get someone else to do this.

So I posted a question on a Do-It-Yourself forum…

I went to a book store and asked the clerk where the Self Help section was.

She said if she told me it would kinda defeat the purpose.

 

[chess-equality]

First time I've seen a fuse that can be opened and closed like a breaker used in solar, I thought it's only a thing from very old AC panels.

 

[Mattb4]

Looking at the picture of the burnt fuse holder it makes me wonder if you have the right fuses installed. There is definite indication of arcing which would only happen if solid connection was not being made. Did the fuse blow?

 

[EliteSolar]

I have no way of telling since the plastic has melted and I cannot extract the fuse from within the holder.

Shall I try to break it to see if the fuse blew ? Does it matter ? Would that mean Im using the wrong fuses ? Why would it drop to zero at night before it blew and stay like that ?

The fuses are the ones I showed in the first post.

 

[OzSolar]

 

[chess-equality]

View attachment 114383

I hope you just made that up.

 

[OzSolar]

This does not appear to have the DC rating on it?

 

[Mattb4]

I have no way of telling since the plastic has melted and I cannot extract the fuse from within the holder.

Shall I try to break it to see if the fuse blew ? Does it matter ?

The fuses are the ones I showed in the first post.

It matters if the fuse did not blow because it would indicate that it was not excessive current enough to blow fuse (short circuit condition). Arcing that can happen due to a bad connection creates heat that eventually damages things. It is like a loose wire at a terminal gets things hot eventually.

The fuses shown and the holder must match and I can not tell from your pictures if they do.

 

[EliteSolar]

This does not appear to have the DC rating on it?


View attachment 114386

From the website :

Type of Input

AC/DC

 

[chess-equality]

View attachment 114383

Another addition to the collection?

Interface Hall of Shame

 

[Mattb4]

View attachment 114383

Hey, it was right.

 

[Quattrohead]

Those type fuse holders are junk, I had one burn up for no apparent reason. I was operating it within the limits specified.
Circuit breakers for me from then on.

 

[OzSolar]

From the website :

Type of Input

AC/DC

Sorry the rating on the fuse holder itself is the only thing I would go by.

 

[BradCagle]

Just carrying current, not arc on closing?

Yes just carrying current

Any chance it was wire to terminal, or do you think it was clip contact to fuse?

I double checked, and tightened the wire/terminal connection.

The clips in the holder are very tight, takes some good effort to close/open

What fraction of rated current?

Probably running close to max

The holder I had was a Chinese (random name) 32a/500v

The fuse was from midnight solar 30a

I can without a doubt say the bulk of the heat was coming from the center mass of the fuse area.

 

[EliteSolar]

It matters if the fuse did not blow because it would indicate that it was not excessive current enough to blow fuse (short circuit condition). Arcing that can happen due to a bad connection creates heat that eventually damages things. It is like a loose wire at a terminal gets things hot eventually.

The fuses shown and the holder must match and I can not tell from your pictures if they do.

I managed to break the fuse holder and extract the fuse and its good?



But even at night when I tried to close both fuses , the voltage dropped everywhere to 0 , how would that explain a loose connection ?

Im pretty sure I checked the voltage seconds before it blew and it was again 0 on all ends on the fuses but Im not totally sure

 

[chess-equality]

I managed to break the fuse holder and extract the fuse and its good?
View attachment 114389

That is continuity and it beeps?

 

[EliteSolar]

That is continuity and it beeps?

correct

 

[chess-equality]

Those type fuse holders are junk, I had one burn up for no apparent reason. I was operating it within the limits specified.
Circuit breakers for me from then on.

This...

 

[EliteSolar]

This is the product description :

Hager 32A 1-pole fuse disconnector 10.3X38 1 module LSN501​

---

Brand: Hager
Cod: HAG LSN501 EAN: 3250614120077
Hager disconnectable fuse switch with the following characteristics:

• Nominal operating voltage AC 690 Vac
• Type of supply voltage AC/DC
• Rated insulation voltage 1000 V
• Rated fault withstand current 6000 V
• Nominal frequency 50 to 60 Hz
• Rated current In 32A
• 1 pole
• 1 module
• IP2X enclosure degree of protection
• DIN rail mounting type o (symmetrical)
• Fuse size 10 x 38

It's supposed to be a good company and it is made in France, not doubting that it could be crap , its just not made in china if that says anything.


But how would this explain that when I closed both fuses the voltage would read 0v on the input and output of the fuses before it caught fire ?

 

[Mattb4]

I managed to break the fuse holder and extract the fuse and its good?



But even at night when I tried to close both fuses , the voltage dropped everywhere to 0 , how would that explain a loose connection ?

Im pretty sure I checked the voltage seconds before it blew and it was again 0 on all ends on the fuses

I am not there to see how you are measuring voltage. I am just looking at your pictures and going by things like checking the fuse to see if it blew to try to troubleshoot what happened.

Since the fuse did not blow it is likely that the problem becomes the fuse connection in the fuse holder. That could be from wrong size of fuse, fuse holder having bad spring connectors, something between fuse and spring clips or even the connection of the spring clip to wire terminals.

 

[EliteSolar]

Guys I think we nailed it!

I took the fuse box with the fuse inside and I shook and rotate gently and it was loosing the continuity beep!

DID WE SOLVE THE MYSTERY ?

But how would it also explain why I was getting 0v when I was closing voth fuse box before I caught fire ?

 

[Hedges]

Hi , as I said my LSC is 11.07A and LMP 10.57 and my fuse is 12amp , I know not ideal, but doesnt explain the problems I have, does it ? I am not having any load on the AC output , I just want to power the inverter for start.

Fuse should be 1.56x Isc, 1.56 x 11.07A = 17.3A minimum. Probably 20A max is recommended on PV panel label.

The 12A fuse should not be the problem by itself, but it would be running near maximum temperature rating, and twice as many degrees rise as with appropriate fuse. But still shouldn't burn.

Loose wire connection seems more likely.

So what you say , that if the fuse holder shorts the PV string , that explains why it didnt burn last night at sunset, it was quite dark ( I had like 250V ? instead of 330V ~ ) and the voltage drop stayed at 0, as I explained before , but burnt today when there was full sun ( it was around 330V I think when it burnt ) ?

So you closed fuse holder in near dark, not with much sun, and also did not open it with much sun? And it still burned?
That takes care of "don't make/break under load"

I checked with the multimeter that my positive and negative are correct.

I tried to find switches but DC not available. So the only way to close the circuit is to close the fuse , or connect the mc4 cables ( or connect directly to inverter ( I would never do that for safety reasons ) .

When I closed both fuses voltage dropped to zero before or after the fuse. 2nd time I tried it after I checked all my cables , one fuse holder caught on fire .

"both fuses" - one in positive lead and one in negative lead of a single PV string?
Or two PV strings, one fuse for each? (check polarity of both strings. Make sure both match intended connection to inverter.)

So the problem really is why is the inverter shorting the PV array ?

You could remove positive wire(s) from inverter, cap with wire nut for safety, repeat experiment. That way only PV strings and fuses are involved, not the inverter.

Thank you all for your responses I highly appreciate it because I can't get anyone near me to help me with my setup. And I also love to learn new things ( without dying hopefully )

What is your location?

Guys I think we nailed it!

I took the fuse box with the fuse inside and I shook and rotate gently and it was loosing the continuity beep!

DID WE SOLVE THE MYSTERY ?

But how would it also explain why I was getting 0v when I was closing voth fuse box before I caught fire ?

If wrong size fuse, not held securely by clips, that would explain burning. (Only when current flowing.)

But zero volts means either no power applied, or wires shorting positive to negative.

With inverter disconnected, you can check every connection and fuse holder for voltage with DMM before connecting/closing.