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  • Fuse question...

    I have built a medium sized portable solar generator for camping and home emergency (power outage use). I have a 300w solar panel 24v going into a 30a solar controller. Should I have a fuse between the panel and inverter, and what would be recommended if needed? Thanks Ken

  • #2
    While not necessary to install a fuse for a single solar panel the cost is usually low and it will protect the wire between the panel and CC if there is a short circuit.

    As for the size. It depends on the Isc rating of that 300 watt panel. There is usually some mention of the max fuse size on the panel data.

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    • #3
      Thank you Suneagle! Just had a bad situation about an hour ago... my new Krueger 1500w inverter blew up right after I turned it on this morning. Just called amazon to return it.

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      • #4
        A fuse between a cc and a single solar panel does nothing to protect an otherwise well designed system. The fuse between the battery and cc is the important one. The *minimum* fuse rating on the panel generally applies only if the array has at least three panels/strings in parallel.
        CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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        • #5
          The manual for my Morningstar Tristar controller said a fuse between the panels and controller is required for building codes. However, like sensij said there isn't enough current in that path to be much of a danger to anything. But having a convenient way to disconnect the panels from the controller, by either pulling a fuse, tripping a circuit breaker, or a simple switch, is very useful if you need to disconnect the controller from the batteries since you don't want current coming into the controller if it isn't connected to a battery.
          I'm an RV camper with 470 watts of solar

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          • #6
            Code does not require the fuse between the panel and cc in this case, despite what the manual may suggest. Agreed that some kind of dc disconnect is nice to have.
            Last edited by sensij; 06-30-2016, 11:22 AM.
            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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            • #7
              The fuses nneed to be between the battery and
              charge controller (about a 20a fuse - depending on the wire gauge used)
              Loads (inverter) more like a 90A fuse, go with what the inverter mfg suggests and wire gauge dictates.

              Wire Gauge and fuses. The fuse it there to only protect the wire (keep it from burning up) There are many wire/amp tables,
              as long as the wire is rated to carry at least the amperage of the fuse, you should be safe. You can use larger wire to reduce voltage drop
              Legal:
              20A fuse (or circuit breaker) with 10ga wire
              20A fuse w/ 4ga wire

              dangerous:
              20A fuse 14ga wire
              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

              solar: http://tinyurl.com/LMR-Solar
              gen: http://tinyurl.com/LMR-Lister

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              • #8
                Originally posted by ewarnerusa View Post
                The manual for my Morningstar Tristar controller said a fuse between the panels and controller is required for building codes.
                That is a lie. The fuses go on the battery term post.




                A fuse between the Panel and Controller is not required or needed for anything. It is called CYA for idiots.


                MSEE, PE

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                • ewarnerusa
                  ewarnerusa commented
                  Editing a comment
                  I was wrong. I looked again and it makes a statement about requiring a disconnect from the power supply incorporated into the fixed wiring in the "Safety and Regulatory Information" section. I had assumed the panels were a form of power supply and that this alludes to a regulatory requirement. The installation diagram most certainly does indicate a disconnect between panels and controller as well as between the battery and controller. And I mentioned a useful reason for having one, acknowledging that it is not related to wiring protection. Every time a I change a controller parameter, I must cycle power to the controller to reset it. The array must be disconnected first and the breaker is a convenient way to do it.
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