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Thread: Time Delay or Fast Acting Fuses for Supply Side Connections

  1. #1
    Join Date
    Oct 2011
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    Time Delay or Fast Acting Fuses for Supply Side Connections

    Wondering what others are using for fuses in the AC disconnects with supply side connections, time delay or fast acting fuses? Since there isn't any surge with grid tied inverters it seems like fast acting would be the way to go but curious to hear other's opinions.

  2. #2
    Join Date
    Jul 2018
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    US
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    17
    I always use time delay dual element fuses. Sometimes voltage sags and current increases and when the fuses are in a box in direct sunlight during the summer you could get false tripping of your fuses. My engineered plans always call for time delayed dual element fuses.

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  3. #3
    Join Date
    Sep 2012
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    CA, US
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    132
    On a job of ours the utility (PGE) required Fast Acting. Not sure if that was specific to their transformer located there or that is standard for them.

  4. #4
    Join Date
    Jul 2018
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    US
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    17
    What was the overall ac wattage and voltage of the system and what size fuses did you use? I know here in kansas and missouri if you use a 7.6kw inverter with 40 amp fuses or an 11.4kw inverter with 60 amp fuses we can get a few false tips in the heat of the summer.

    Sent from my SM-G955U using Tapatalk

  5. #5
    Join Date
    Nov 2015
    Location
    CA, USA
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    681
    I always specify RK1 or RK5 fuses to provide a high AIC rating for the disconnect, so I just don't have to worry about the available fault current from the utility. The default type H fuses only give a 10kAIC rating.

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