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ws9876
ws9876 Solar Expert Posts: 440 ✭✭✭
in Off Grid Solar & Battery Systems #1
I have an old Franklin well control box for a 2hp submersible pump. It says on it max 14 amps and its 230v.
It has a block in there to join wires coming and going. It looks substantial. Do you think there would be a problem using it in a 120v
circuit requiring 30 amps max.Like a charge controller?
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    Don't use it.   If it's rated for 14A, why would you think 30A would be safe, that over 100% overload !!
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  • rgk1
    rgk1 Solar Expert Posts: 134 ✭✭✭
    #3
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    mike95490, this brings up a probably silly question but one I have often had in passing.  In reference to protection, is an amp just an amp no matter the voltage?
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited August 2019 #4
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    An amp is an amp, the voltage rating however has to do with dialetric strength, which is why a maximum voltage is used in conjunction with the amp rating. The AC current  rating would not be the same as DC current , DC could sustain an arc in a fuse designed for AC still allowing current to flow even when the element has failed. AC is sinusoidal, meaning  that current and voltage will be at a zero potential 50 or 60 times per second depending on frequency, 50 or 60Hz, it's this cycling that allows the arc to quench, so if there is no specific DC rating and only an AC rating assume it's not compatible 

    With regards to circuit breakers, AC circuit breakers are generally not compatible with DC, there are a few exceptions, if they are rated for both they will have markings stating so, just like fuses.

    Any eloborations welcome.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,044 ✭✭✭✭✭
    #5
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    mcgivor said:

    With regards to circuit breakers, AC circuit breakers are generally not compatible with DC, there are a few exceptions, 
    The Square D QO line of circuit breakers being one exception. There is plenty of documentation online regarding their DC compatibility if you take the time to search the companies website.. The various QO models have varying DC voltage limits.

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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #6
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    I believe that the OP is pondering using the TERMINAL strips of the above mentioned Franklin box, not the breaker.  That said, IMHO if the lugs are substantial and fit the wire sized I wouldn’t really have a problem with it.  You can always check the lugs under load with a IR thermometer to see if they are heating abnormally.  I agree 100% about the breaker oversize however if I am wrong on my assumptions.

    Tony
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