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Thread: voltage drop

  1. #1
    DIY Member ugabulldog's Avatar
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    Default voltage drop

    Voltage drop was calculated for #10 wire and I am very close (right at) to the max run so I think I will need to size down to #8 wire running 390 ft. to well,....wire in well is 240' of #10 wire, is this ok to mix 8 & 10 to compensate for volt drop?
    Last edited by ugabulldog; 01-20-2011 at 06:16 PM.

  2. #2
    Moderator valveman's Avatar
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    Actually having the maximum recommended cable length is a good thing. It makes a natural soft starter. #10 wire will go 630' with a 1 HP motor. It doesn't hurt anything to start with #8, except that it won't give you the soft start like 630' of #10 will do.

    "Reduced-voltage starters may not be required if the maximum recommended cable length is used. With maximum recommended cable length there is a 5% voltage drop in the cable at running amps, resulting in about 20% reduction in starting current and about 36% reduction in starting torque compared to having rated voltage at the motor. This may be enough reduction in starting current so that reduced-voltage starters are not required."

    Heres the link;
    http://www.franklin-electric.com/aim...l/page-36.aspx

  3. #3
    General Engineering Contractor ballvalve's Avatar
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    I have almost the exact same setup and pump is happy for several years and runs on 239 volts after start up. I may even have a 1.5hp motor on it.

    But where is the control box? at the beginning of the run, or at the well head?

  4. #4
    Moderator valveman's Avatar
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    I don't think it will make much difference where the control box is. But I think the starting torque would be less the further away the control box is.

  5. #5
    DIY Member ugabulldog's Avatar
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    Quote Originally Posted by valveman View Post
    Actually having the maximum recommended cable length is a good thing. It makes a natural soft starter. #10 wire will go 630' with a 1 HP motor. It doesn't hurt anything to start with #8, except that it won't give you the soft start like 630' of #10 will do.

    "Reduced-voltage starters may not be required if the maximum recommended cable length is used. With maximum recommended cable length there is a 5% voltage drop in the cable at running amps, resulting in about 20% reduction in starting current and about 36% reduction in starting torque compared to having rated voltage at the motor. This may be enough reduction in starting current so that reduced-voltage starters are not required."

    Heres the link;
    http://www.franklin-electric.com/aim...l/page-36.aspx
    That is my problem,...I am a little over 630', by a few feet, so I should go with #8, in fear of burning pump up faster, correct?
    Last edited by ugabulldog; 01-22-2011 at 06:57 AM.

  6. #6
    General Engineering Contractor ballvalve's Avatar
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    You can mix wire sizes. But the charts have much leeway in them. Dont sweat a few feet.

  7. #7
    DIY Member ugabulldog's Avatar
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    control box is at the well head, does this make a differnce ballvalve or anyone??

  8. #8
    Well Drilling/Service justwater's Avatar
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    it's fine, no worries.

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