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RichieRich

Solar fuses keep blowing

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I’m having an issue with one of my strings. 
I keeps blowing a fuse once every 3 weeks or so. It’s done this 3 times 
I have  6X 290w panels 3S2P on that line. and therefore should only be getting a max of 20amps. However I’m blowing a 30amp fuse. Now I have another string of 6 panels facing the same way wired exactly the same and its fuse never blows. 

Today when the fuse blew my solar was putting out 88v and 2880w  from 15 panels which should equate to around 13amps on that string. 
 

In the past when I’ve replaced the fuse I’ve tested the current draw on each of my strings and all the numbers and where what they supposed to be. 

Any ideas? 
 

 

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Unfortunately I’m nowhere near my system at the moment and won’t be for the next 3 weeks. It’s a standard 32amp dc  fuse holder and a 10mm x 38mm 30amp dc solar fuse being used. The cable run is around 10m and I’ve used 6m2 solar cable.  

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Posted (edited)

Hi 

If I am correct you have  2 strings in parallel  of 3 pv panels in series. Each string is just over 9amps which gives you the 20amps  in total.

It is unlikely that the 30amp fuse will blow due to overcurrent.

To my knowledge and experience with fuses the most likely cause would be the following.

A fuse when it blows from overcurrent will usually  fuse in the middle of the  fuse wire. this can only be seen if the fuse wire can be seen eg. glass fuses.

I am sure the fuse wire cannot be seen because it is a ceramic fuse.

The fuse can also  blow or fuse, in this case melt because of a bad contact in the fuse holder. The resistance caused by the bad contact acts as an element.

The fuse wire will melt off the end of the fuse metal contact because of heat.

It will be best just to replace the fuse holder and the fuse. Also check that the wires are securely fastened which can cause the same problem.

I hope this info will solve your problem.

 

 

 

Edited by Peter Topp

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7 hours ago, Peter Topp said:

I am sure the fuse wire cannot be seen because it is a ceramic fuse.

You can open it up. If it burns off at the end, then once you open it up and poor out the silica inside, you should theoretically have an intact fuse wire attached only on the one end.

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Thank guys for the support and response. I managed to get someone to change the fuse and the fuse holder last night. So lets see how it goes over the next few weeks. I'll check temperatures when i get back home. 

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On 2020/03/11 at 7:37 PM, RichieRich said:

I have  6X 290w panels 3S2P on that line

Hi Richie hope your problem is sorted, if it still happens it might be worth confirming that the panels are indeed connected 3S2P and not 2S3P because that could cause it to possibly reach the 30A range on peak PV and blow a fuse. 

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On 2020/03/13 at 11:35 PM, Gerrie said:if it still happens it might be worth confirming that the panels are indeed connected 3S2P and not 2S3P

So far so good hopefully it was just a dodgy fuse holder. They definitely 3S2P 60 cells panels with a combined open voltage of about 103v. When I get back to SA double check everything. 
 

 

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Seems I have also blown a fuse yesterday afternoon. Will follow some of the advice given and provide feedback once I have a replacement fuse at hand.

 

 

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24 minutes ago, RichieRich said:

So far mine has been behaving itself since changing the fuse holder. 

The holder that blew a fuse was a Johnson, it has a light to indicate which fuse blew, so was easy to spot since I only realised my east string is dead this morning. 

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On 2020/03/18 at 8:17 AM, PaBz0r said:

Seems I have also blown a fuse yesterday afternoon. Will follow some of the advice given and provide feedback once I have a replacement fuse at hand.

 

 

And... it was an AC fuse.. nice....

 

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On 2020/03/19 at 9:34 AM, PaBz0r said:

And... it was an AC fuse.. nice....

Yes,  We always have to double check the goods supplied, Some of the sales guys don’t know the difference and on top of that the guy in the back store pulling the goods even knows less. I see this everyday, I return at least 1 out of 10 items that is supplied wrong.

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On 2020/03/21 at 7:13 AM, Gerrie said:

Yes,  We always have to double check the goods supplied, Some of the sales guys don’t know the difference and on top of that the guy in the back store pulling the goods even knows less. I see this everyday, I return at least 1 out of 10 items that is supplied wrong.

Funny enough.. this was done on installation.. and it turns out that only 1 fuse out the 6 was a dc fuse. This is what happens when people are left unsupervised and want to complete the job and make due with what they have in a toolbox somewhere. I was pretty livid to say the least.

I am still planning on my next approach as on closer inspection 3 out of the 6 fuse holders are AC fuse holders.. 

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Just a general question about this: Are DC fuses a specific type of item?

I have fuses in the line between inverter and battery and between the inverter and each string of PV panels. I have no spares and will have to buy a spare set just in case.

So

1) What are the important markings I should look for?

2) Where in Randburg can I buy them (assuming such shops are actually open, but that's another matter)?

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6 hours ago, Richard Mackay said:

Try Lido Electrical in Strijdom Park  Ph: 011 791 6070

They are quite sharp I have found..

I know them. Thanks. I'll have to hope nothing pops in the next 3 weeks, other wise it's tin foil

joking...

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Just now, Bobster said:

Nothing a sawn off teaspoon won't sort out.

I say this but I remember being an appy in what was then the Department of Posts and Telecommunications. All the exchange equipment back then ran on 50V DC and they used to have DC bus bars above every rack of equipment. The local bus bars were connected to a trunk. And all the trunks eventually connected to the main bus bars which were massive and ran the length of the exchange.

One day being bored (and actually incredibly stupid) a mate and I decided to throw a pair of sidecutters so that they'd land across the main bus bar. Just to see what would happen. What were we thinking?

Anyway, we did, and the sidecutters basically went poof! and vanished in a cloud of sidecutter particles.

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4 hours ago, Bobster said:

I say this but I remember being an appy in what was then the Department of Posts and Telecommunications. All the exchange equipment back then ran on 50V DC and they used to have DC bus bars above every rack of equipment. The local bus bars were connected to a trunk. And all the trunks eventually connected to the main bus bars which were massive and ran the length of the exchange.

There was probably a battery room at the end of the main bus bars with banks of massive 2V cells?

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