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Blew a 30 amp fuse?!!? Say What?

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  • Blew a 30 amp fuse?!!? Say What?

    Ok. I have a 100 watt solar panel. I was using 16 ga. Wire this morning (16 ga. output from charge controller. Input is 10 ga 25 ft. Copper.) it's going into a 300 watt pure since inverter. Powering a 60 watt mini fridge. ) it was working fine, through a car Bart 12v. 12.7 volts. Then it was 12.1 volts but still going. I noticed wire clamps getting warm/ hot after 1/2 hour so I upgraded the output wire from charge controller to 12ga copper. Turned on the inverter, fridge still plugged in, and it blew the 30 amp fuse.
    Any ideas? Thinking of using a power strip next time so I have on and off.
    Last edited by SolarRV; 06-28-2017, 02:04 PM.

  • #2
    Originally posted by SolarRV View Post
    Ok. I have a 100 watt solar panel. I was using 16 ga. Wire this morning (16 ga. output from charge controller. Input is 10 ga 25 ft. Copper.) it's going into a 300 watt pure since inverter. Powering a 60 watt mini fridge. ) it was working fine, through a car Bart 12v. 12.7 volts. Then it was 12.1 volts but still going. I noticed wire clamps getting warm/ hot after 1/2 hour so I upgraded the output wire from charge controller to 12ga copper. Turned on the inverter, fridge still plugged in, and it blew the 30 amp fuse.
    Any ideas? Thinking of using a power strip next time so I have on and off.
    Your most likely problem is a short-cycle start. Many compressors can not restart quickly after being shut down since their high side pressure is much higher than normal. (Many air conditioners and some refrigerators have a short cycle timer that prevents this.) Even if it can restart it takes a lot more power. Let it sit for 10-15 minutes then try again.

    Other possibilities include higher current needed due to the lower voltage and just plain surge. A fridge is going to need several amps to start, and 4 amps at 120 volts = 480 watts, which is 37 amps at 12.7 volts (and 40 amps at 12 volts.)

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    • #3
      Ah. Ok. So I'm trying to figure out how many amps my inverter can take. It only says 240VA output. So I'm thinking a 40 amp fuse at least if I can get one? But the calculator says only 20 amp single phase. I had a 30 amp fuse in it. The fridge draws 60 watts. I'll try again tomorrow with a 30 amp fuse. Do I need a larger inverter?
      http://www.rapidtables.com/calc/elec...calculator.htm

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      • #4
        Originally posted by SolarRV View Post
        Ah. Ok. So I'm trying to figure out how many amps my inverter can take. It only says 240VA output.
        240VA continuous or surge?

        240VA means 120V at 2A, or 12V at 20A. You have to add surge to that, as well as consider lowest operating voltage (operation at 11V takes more current than operation at 13.5V - not that you should be operating at 11V anyway.)

        So I'm thinking a 40 amp fuse at least if I can get one? But the calculator says only 20 amp single phase. I had a 30 amp fuse in it. The fridge draws 60 watts. I'll try again tomorrow with a 30 amp fuse. Do I need a larger inverter?
        If the fridge will start normally (i.e. not during a short cycle, but during normal operation) then you probably don't need a new inverter. And if you avoid short cycles you probably don't even need a 40A fuse.

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        • #5
          Queer Electrons blow the fuses.

          Seriously you have several issues.

          A 16 AWG wire from the panel to controller is just fine, that will not cause current to increase, it will cause voltage to sag if longer than So if you have a 100 watt panel, with 25 feet 1-Way between Panel and Controller needs to be !0 AWG to limit voltage drop to 3% or less. But that i snot what is causing you fuse to blow

          With a 100 watt panel and 12 volt battery, you need at least a 10 amp controller. Again 10 amps is no problem on a 16 AWG wire as long as the 1-Way distance is 5-feet or less. Again not the cause of your fuse blowing.

          Now let's get to your problem. If wires between the battery and Inverter are getting warm or hot means you have either to small of a wire, bad connections, or both. A 300 watt TSW inverter pulls 25 amps at 300 watts, and 50 amps at surge of 600 watts. As you loose voltage on the wiring to the Inverter, current must go up to compensate for lost voltage. Minimum wire size for a 12 volt 30-Amp circuit is 10 AWG for rup to 6 feet. 10 AWg will get you up to.

          Morro to the story is use !0 AWG wire for everything you have to keep Queer Electrons away and make sure you have good connections to keep them out of the house. .
          Last edited by SunEagle; 06-29-2017, 09:00 AM. Reason: correct surge wattage
          MSEE, PE

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          • #6
            I guess I still don't know where in the circuit that 30A fuse is. I can assume it is on the DC side between the battery and inverter. But as Sunking states an inverter usually has a surge rating and can draw high amps for a brief time.

            Hot wires is a good indicator that they are too small for the amp load they are handling. Best to up-size ever wire to at least #10 AWG

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            • #7
              Yes on fuse local. Wire was 14 or 16 ga getting hot. I'll wait till I can upgrade the wire to try again.

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              • #8
                Originally posted by SolarRV View Post
                Yes on fuse local. Wire was 14 or 16 ga getting hot. I'll wait till I can upgrade the wire to try again.
                Just make sure you size your fuse to protect the wire. IMO a 30A fuse is too big for even a 14 ga wire so you may have been lucky to blow the fuse instead of burning up the wire insulation.

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                • #9
                  Originally posted by SolarRV View Post
                  Yes on fuse local. Wire was 14 or 16 ga getting hot. I'll wait till I can upgrade the wire to try again.
                  You cannot use a 14 or 16 AWG wire on a fuse. Must be 10 AWG or larger. It is getting hot because you are running way to much current.

                  MSEE, PE

                  Comment


                  • #10
                    Originally posted by sunking View Post
                    you cannot use a 14 or 16 awg wire on a [30a] fuse. Must be 10 awg or larger. It is getting hot because you are running way to much current.
                    fify

                    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                    • #11
                      Originally posted by inetdog View Post
                      fify
                      My bad. Cannot use 14 or 16 AWG with a 30 Amp Fuse. 10 AWG minimum.

                      He has given two clues.

                      Wire getting hot, and Inverter Tripping off-line from under voltage. My guess is both battery and wire is to small.
                      MSEE, PE

                      Comment


                      • #12
                        Originally posted by SolarRV View Post
                        Ok. I have a 100 watt solar panel. I was using 16 ga. Wire this morning (16 ga. output from charge controller. Input is 10 ga 25 ft. Copper.) it's going into a 300 watt pure since inverter. Powering a 60 watt mini fridge. ) it was working fine, through a car Bart 12v. 12.7 volts. Then it was 12.1 volts but still going. I noticed wire clamps getting warm/ hot after 1/2 hour so I upgraded the output wire from charge controller to 12ga copper. Turned on the inverter, fridge still plugged in, and it blew the 30 amp fuse.
                        Any ideas? Thinking of using a power strip next time so I have on and off.
                        You wrote "... car Bart 12v ..."
                        Did you mean "Car Battery 12V" ?
                        Maybe, replace with a Deep Cycle Battery, like a Golf Car GC12 12 Volt Battery or better?
                        An automotive SLI type battery cannot be deep cycled very many times ( < 50 ) before the voltage will sag under load.

                        Buy a pair of professionally crimped battery-to-inverter cables.
                        The hole in the lug should be just big enough to slide over the battery stud, then the washer, and finally the nut.
                        Some professionally crimped large cables shown below ...






                        Small gauge wire can heat up and start a fire, be safe.
                        You life is worth it.
                        Last edited by NEOH; 06-30-2017, 08:48 PM.

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