Is this normal?

intel415intel415 Solar Expert Posts: 31
Hello folks,

My first burnt fuse came after 6 months lol. Suddenly everything was stopped working. I was suspecting the inverter was faulty, walked closer to my setup today and saw the 100A fuse has been burn pretty bad, even the wire to the positive side of the inverter melted a little bit. So i replace with a new 100A fuse. Everything is back to normal wonderful lol. After i replaced the fuse, i touch the fuse holder it feels warm/hot the side to the positive input of the inverter, is this normal? Thanks guys.

Setup
morningstar 300W
2x t105
100A fuse between battery and inverter.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Is this normal?

    No, that is not normal.
    Under normal circumstances the MS 300 draw about 25 Amps at peak power and wouldn't even phase that 100 Amp fuse. At its surge rating of 600 Watts its only about 50 Amps. Even at minimum operating Voltage and maximum power output it shouldn't be heating a 100 Amp fuse.

    This leaves me wondering what size wires are being used and what type of fuse/holder is on that wire.
  • intel415intel415 Solar Expert Posts: 31
    Re: Is this normal?

    I'm using 4AWG and ANL 100A audio fuse got off from ebay please see picture. Can a bad inverter causing this? thanks
  • intel415intel415 Solar Expert Posts: 31
    Re: Is this normal?

    I took some pics showing the fuse holder. I circled red thats the part where it feels warm/hot to touch. Faulty inverter? what do u think?

    Thanks
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Is this normal?

    The 4 AWG should certainly be sufficient. Not sure I'd pick those fuses for the app but they're probably easily available.

    Now what you need to do is difficult, because you really need one of those clamp-on DC Ammeters Bill is always talking about: you need to measure the actual current going to the inverter. If it is within limits for the load put on it, then I would suspect that the mounting/ends of these ANL fuses are not actually sufficiently sized (we see this a lot in the automotive blade fuses - El Cheapos where they've slimmed the contacts down to minimum making them weaker than the actual fuse).

    If the current drawn is out of spec for the load on the inverter, then it is drawing too much current itself. The good news is that Morningstar's customer service is second to none, and if you contact them you should get excellent results.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Is this normal?
    intel415 wrote: »
    I'm using 4AWG and ANL 100A audio fuse got off from ebay please see picture. Can a bad inverter causing this? thanks
    The two main reasons for the end of a fuse heating up and the plastic body charring or offgassing while the fuse element itself (narrow part in the center) remains unmelted are:

    1. A bad connection between the fuse and the fuseholder or the terminal on the end of one of the cables.
    2. A badly made connector which is heating up between the copper and the terminal lug.

    Either of these conditions can affect primarily one end of the fuse, which appears to be the case here.

    If you feel only one of the wire connections to a fuse holder or only one end of the fuse getting hot, then you have a bad connection. The normal operation of the fuse under severe overcurrent will melt (or vaporise) the link in the middle before either end gets very hot.

    I can't think of anything that the inverter could be doing to cause this (other than drawing the current it needs through the fuseholder!)
    SMA SB 3000, old BP panels.
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Is this normal?

    my best guess is high resistance at the connection to the fuse, either the lug, or the fuse itself. Put an ohm meter on the fuse and see how much resistance it has. Bad crimp on the lugs, or the fuse itself might be suspect as well.

    Tony
  • intel415intel415 Solar Expert Posts: 31
    Re: Is this normal?

    Now the inverter is completely dead, it doesnt turn on anymore only my 12v cooling fan is on. lights had been blinking red before i notice burn on the fuse and the meltdown on the wire Ms is sending me a replacement.

    Cari do you think it would be better to use a fast blown glass fuse before the inverter then ANL type?

    Thanks again.
  • Joe_BJoe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    Re: Is this normal?
    intel415 wrote: »
    Now the inverter is completely dead, it doesnt turn on anymore only my 12v cooling fan is on. lights had been blinking red before i notice burn on the fuse and the meltdown on the wire Ms is sending me a replacement.

    Cari do you think it would be better to use a fast blown glass fuse before the inverter then ANL type?

    Thanks again.

    Most inverters require a class "T" type fuse. Here is an example

    http://www.solar-electric.com/nsearch.html?catalog=wind-sun&query=fuse&x=0&y=0
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Is this normal?
    Joe_B wrote: »
    Most inverters require a class "T" type fuse. Here is an example

    http://www.solar-electric.com/nsearch.html?catalog=wind-sun&query=fuse&x=0&y=0

    And here is a time-delay vs. current graph for a typical class "T" fuse. It is specifically designed to blow almost as fast as a transistor under a short circuit condition and to be able to interrupt ungodly amounts of short circuit current. The typical 12 volt fuse like the one in your picture may be hard pressed to interrupt a high current arc, especially with a DC voltage higher than 12 volts or battery capacity larger than your typical auto cranking battery. (Think 1000 AH of AGM, for instance.)
    Compare that to the graph for a typical ANL type fuse, which basically does not blow at all in less than a tenth of a second even at 600% overload. Compare this to the 1/100 second blow at 500% from the T.

    It will still not save your inverter from self-destructing (look at the infinite hold time at 150%, for example) but it will do its part to insure that only the inverter fails.

    Glass fuses generally will not have the DC interrupting ratings that you need, regardless of their time delay.
    SMA SB 3000, old BP panels.
  • intel415intel415 Solar Expert Posts: 31
    Re: Is this normal?

    thanks guys i will look into class t fuse.

    Guess what inetdg was right, it was a bad connecting where the part got burnt. Maybe when i was putting a 12v cooling fan next to the inverter, i loosen the wire a bit somehow. I tighten everything guess what everything is back to normal once again :) Inverter is not dead.

    Thanks guys.
  • vtmapsvtmaps Solar Expert Posts: 3,739 ✭✭✭✭
    Re: Is this normal?
    intel415 wrote: »
    I tighten everything guess what everything is back to normal once again

    Do you realize that copper flows? When you tighten a connection to a copper wire, you should wait 30 minutes and then tighten it again.
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Is this normal?
    vtmaps wrote: »
    Do you realize that copper flows? When you tighten a connection to a copper wire, you should wait 30 minutes and then tighten it again.
    --vtMaps

    That is one very good reason to use terminal lugs (crimped or soldered) rather than bolting the wires directly!

    Also, directly bolting the wire is not advisable for stranded wire in any case. Especially with large diameters.
    SMA SB 3000, old BP panels.
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Is this normal?

    And fastening the cables where they enter to bolted connections so that somebody moving the cable around does not loosen your bolted connections (because of the large diameter/stiff cables).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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