DC fuse caught fire! Help ?

[EliteSolar]

FIXED : THE PROBLEM WAS THAT I DONT KNOW HOW TO PROPERLY USE A DIGITAL MULTIMETER ( I HAD REVERSED THE RED BLACK LEADS AND I DIDNT NOTICE SO I MESSED UP THE POLARITIES. ALSO, NEVER OPEN/CLOSE DC FUSES HOLDERS WHEN THERE IS LOAD, ESPECIALLY WITH HIGH VOLTAGE PV STRINGS

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

 

[Kornbread]

Scary, because that fuse holder looks a lot like the generic Chinese made ones found in many combiner boxes. 1000v dc, 12a, 30ka interrupt fuse. Is the fuse still good and was it the housing that burned up?

 

[cods4]

It sounds like you have a short somewhere., either in the inverter or in the wiring somewhere.
I'm guessing the reason it arced and caught fire is that you opened the fuse switch under load. The removable fuse obviously isn't designed for that, so next time try this at night.

I suspect the fuse is still fine and should work correctly if it were to blow as the fuse has arc quenching sand inside it to stop the arc (and fire).

 

[EliteSolar]

The first time I just connected the panels to the AIO.. nothing else connected. What do you mean Im connecting under load? The inverter was off position. How am I supposed to do it?

The housing all caught fire and melted completely. so I cant open it and I dont know if the fuse is still good but I highly doubt it

the photo i posted above is a good one.not the burnt one

 

[Miles B]

This has to be either a high resistance joint in the housing, or you shorted the panels through the fuses.

 

[EliteSolar]

What would a high resistance joint in the house practically mean? Why did the voltage drop from 320v to 0v when I closed the fuse the first time and it stayed like that for half minute without catching fire? Was the inverter doing it to protect itself? Sorry Im not an expert and Im trying to understand how to proceed

 

[Miles B]

You haven't said what you were testing the voltage across, how your system is laid out etc.

I'm not sure you should be doing this.

 

[Bluedog225]

Agreed that some more detail about your system layout would be helpful.

The hive mind loves photos.

As the US crowd (edit-spelling) wakes up this morning, you will receive some more thoughts.

Sorry about the fire. Glad it wasn’t worse. And welcome to the forum.

 

[acdoctor]

Someone had one of them burn up a while ago but it worked for a while.
Can we get more information.
VOC from your panels label?
Was the 8 in series?
Did you install the fuse or inspect it for proper insulation?
Were you measuring from positive to negative or across the fuse?
Do you have a diagram or picture of the insulation?

 

[EliteSolar]

INFO :

I want to run batteryless for now , just the PV connected to the AIO.

VOC from your panels label?
46V STC

Was the 8 in series?
Yes ( measures 320V )

Did you install the fuse or inspect it for proper insulation?

Insulation you mean the box that holds the fuse ? Yes there was a fuse inside , the one I showed above, sorry if I dont understand exactly the question. It's the first time Im installing this setup

Were you measuring from positive to negative or across the fuse?

When the fuse is open and I measure DC voltage in the input of both the fuses, it is 320V and obviously zero at the outputs of the fuses . When I close both fuses , I got 0volt on all terminals both input and output . When I tried to close just one it measures on the input positive and negative 320V and if I measure the input on open fuse and the output of the other closed fuse I get 320V , so it seems when the inverter is connected , it droped the voltage to 0 .

Then I disconnected and checked everything and when I switched on both fuses , one caught fire.

Do you have a diagram or picture of the insulation?

Is this what you want to see ? Sorry I dont understand

 

[Miles B]

You need to get someone else to do this.

 

[EliteSolar]

I would have already done that if I could find anyone around me that knows how to do it. So it will have to be me .

 

[John Frum]

@EliteSolar check to see if there is voltage on the pv terminals of the all_in_one.
I mean with the pv panels totally isolated.
You should be able to short a string of panels with no real issue.
Lets rule out my suspicion that the fault current is coming from the all_in_one.
Be careful.

 

[EliteSolar]

The voltage on the PV terminals of the AIO is 0 with no cables connected to the AIO at all. I want to run this system batteryless.

Should I start it with batteries and then measure the voltage of the PV terminals ?

 

[John Frum]

The voltage on the PV terminals of the AIO is 0 with no cables connected to the AIO at all. I want to run this system batteryless.

AFAIK most AIOs won't run without batteries.

Should I start it with batteries and then measure the voltage of the PV terminals ?

Do you have batteries on hand?

 

[acdoctor]

If the panel voltage went to 0 when connected you have a short beyond the fuse.
With the inverter off, reconnect and check amperage on PV wire. I think you will find it to be a little below the short circuit amperage.
PV circuit voltage should stay between VOC and MPPT voltage of the string.

 

[John Frum]

Please provide a product link for your AIO so we know what we are dealing with.
Same for the panels.

 

[John Frum]

In light of @acdoctor 's observation...
With the AIO not connected to anything please check for continuity between pv negative and pv positive.

 

[Mattb4]

There is a wiring mistake in your setup. I hope you did not wire the solar (PV) to the battery terminals on the inverter. Your picture shows a red and black going into the PV opening of the inverter casing but a blue and red on the other side but does not show actual connections.

 

[Lilikoi_Heavy_Industries]

Where did you hear that an inverter is supposed to be able to run on PV only? Go back to that source of information for troubleshooting would be my suggestion since they're the people who set you up with some "interesting" expectations.

Sure, it might work for the model you're using, or it might not, but it's not a normal thing to do. Good luck.