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  • Fuses vs circuit breakers and grounding

    Hi All,

    I have a 750 watt array coming into a 60a controller feeding a 24v battery bank leading to a 24v 1500w inverter. I have had lots of conflicting advice with regards to the size and type of fuses I need. I have 4awg wire between the controller and batteries (about 3 feet) and 4awg between the batteries and the inverter (about 8 feet). The inverter Compay (GoPower) suggests a 110A type T fuse. The cable manufacturer suggests a 150A fuse with any 1500 watt inverter. I haven't been able to find any info about what size to put between my controller and battery, but I did just pick up a 150A DC surface mount circuit breaker because someone suggested it. Thoughts? Any reason why I couldn't use a circuit breaker rather than a fuse on both connections (makes disconnecting when required easier).

    I'm also wondering why the fuses would be more like 120A given that the maximum surge is 2400W at 24v. Perhaps because a discharged battery might need to push more current?

    Finally, can I run the ground wire from the inverter into the same ground (leading to buried grounding plate) as my controller?




    Thanks!


  • #2
    I know this doesn't answer all of your questions but it might help a little with determining if you can use a circuit breaker instead of a fuse on both connections.

    https://www.dosupply.com/tech/2017/02/15/what-is-the-difference-between-a-fuse-and-a-circuit-breaker/

    https://www.renogy.com/blog/how-to-fuse-your-solar-system/

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    • #3
      Another problem with fuses. Most (but not all) CANNOT be used to open a circuit for testing. The holders are labeled "touch safe" so you can't shock yourself, but they cannot be opened and removed while energized. The fuse cartridge is rated to "open" the circuit, but not the holder, which is likely to arc and burn.
      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

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      • #4
        Originally posted by Mike90250 View Post
        Another problem with fuses. Most (but not all) CANNOT be used to open a circuit for testing. The holders are labeled "touch safe" so you can't shock yourself, but they cannot be opened and removed while energized. The fuse cartridge is rated to "open" the circuit, but not the holder, which is likely to arc and burn.
        For those of you who may wonder why this distinction, it has to do with where the DC arc is located. When the fuse blows the arc as the fuse element opens is [I]inside[/I] the fuse cartridge and prevented from spreading. In addition there may be substances there designed to help quench the arc.
        When you pull the fuse the arc is between the fuse end and the holder, and can expand to join between the two fuse clips of the holder, without [I]extinguishing an arc[/I] ever being part of the design of the fuse holder.
        Finally, in the worst case the arc at the fuse contacts could well injure you even though the fuse holder is touch [I]voltage[/I] safe.

        SunnyBoy 3000 US, 18 BP Solar 175B panels.

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