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Thread: Stepping up/down voltage from incoming feed???

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    Default Stepping up/down voltage from incoming feed???

    Here is my situation: my home is being built about 2000 feet from my utility transformer which as the end of the utility's line in a very rural, ag area. The utility wanted wayyyy tooo much to extend the line, so I did a little research, some cost comparisons, and found it about 1/3 the price to lay my own cable. I bought a 350kcl cable, and laid it from the transformer to my home. The utility would not supply me with the 480V (I think) from their feed directly, which is what I wanted, so I have the standard 240V service. What I would like to do is to install a step up transformer after my meter to raise the voltage to 480V, then step it down 2000 feet away at the house to 240V. I would like to do this to get more amps at the house. Has anyone had any experience with this sort of thing?

  2. #2
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Typically you would run primary (~3000v-6000v) from the utility to near the house (<250') where the transformer is placed. This cable is typically the customer's responsibility.

    Are you saying the POCO will not let you do this?

    There is NO WAY secondary (240v-480v) would be enough to combat voltge drop @ 2000'.

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    Electrician frenchelectrican's Avatar
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    Did you buy the 350 KCM cable ?? for the entrie run ??


    I am going to be very blunt on this one for 2000' of run IMO that is very serious voltage drop for that kind of distance you will really need oversized secondary wire but what SpeedyPete mention there about the POCO will run the wires normally they will put the transformer close to the house useally 250 feet or less

    but you say you want to boost up with the transformer up to 480 volts then use the second transformer to down step back to 120/240 IMO i think not really worth it becuse you have to deal more dangerous poineal with 480 volts and also the POCO will NOT provide 480 for resdentail service it was written in the NEC code for very long time

    you may want to try talk to the POCO to bury the primary line or run the primary with the post along the way to near to your house you will have to deal with this

    if you really want to do this in your way you will have alot of serious issuse will crop up fast


    Merci , Marc

  4. #4

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    The utility tells me that the voltage at the primary of their transformer is 480V. The 2000 foot cable is in and I have been using it for a year. Voltage drop calculations indicate that I will have about a 8% voltage drop at 100 amp draw, giving 220 at the house. I know that this is quite a bit below the recommended drop but I will not be drawing 100 amp continuous and most appliances are fine at 110V....at more realistic amp draws, I will have a lot less drop. I am interested in using the step up/down transformers to increase the capacity and reduce the drop...

    Yes, the utility would run the line to the house, as I said, but the cost was 4X what it cost me to put in my own line....Again, the utility WILL NOT provide 480V, so what I am asking is, what are the issues with me using a step up and step down transformer to get the voltage up myself? What serious issues will crop up fast? As I said, the cable is in the ground and has been used now for over a year without any issues to date....
    Last edited by cab; 08-24-2007 at 03:05 PM.

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    DIY Senior Member BrianJohn's Avatar
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    I live about 2000' from the utility street connection, I paid $6,000.00 for primary distribution 15 years ago.

    If I had the time at the time I would have run the priimary myself.

    For $6,000.00 dollars you could buy 2-transformers step it up and down if they will only supply 240, If the give you 480 at the street use it if allowed by the AHJ, then step it down at the house, An other alternative would to be to use a 1 to 1 transformer with primary taps set to allow for the VD. Typical taps are in 2.5% increments. Figure an average so at no load you are not at a excessively high voltage.

  6. #6

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    My utility is an electric coop and they wanted about 3X your $6000 to extend their primary. That is why I bought the cable and had it trenched in.

    I am hoping someone will elaborate on what, if any, issues there may be in my plan to install a step up after the meter to take the 240 service to 480V, then step it down at the house 2000 feet away from the 480V to 240V....Any takers?

    Thanks to all who have responded....

  7. #7
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by cab
    Any takers?
    Where is the meter?

    If it will be before the first transformer then the bill will be based on the draw of the primary of the first transformer at 100% 24 hours a day 7 days a week. This would be one hellish bill to pay month after month.

    I think you said;
    Quote Originally Posted by cab
    As I said, the cable is in the ground and has been used now for over a year without any issues to date....
    Then why mess with something that ainít broke?

  8. #8

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    Can you explain a bit why a step-up/step-down set of transformers placed after the meter would run the bill up? As I understand it, transformers don't draw current on their own...

    I am looking at this to increase my capacity should I wish to add additional loads...

    Thanks again.

  9. #9
    Licensed Electrical Contractor Speedy Petey's Avatar
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    You will not "gain" much ampacity, if any at all. All you will do with your plan is lower voltage drop.
    You still only have a cable that is just so big. Stepping up and back down will not make the cable any bigger.

    Your thoughts on VD are a bit flawed as well. 120v loads have MUCH higher VD issues than 240v. Thing is your service is what you are worried about. That is 120/240v. In the eyes of VD it is more 240v than anything else. Residential services are typically pretty well balanced.

    Sorry, but I find your particular situation very hard to believe. Not that I think you are lieing, but that your POCO is SO stubborn on this issue.
    They HAVE to allow you primary for a distance like that. Even at 480v (which is NOT primary BTW) that distance is too far for anything practicable.
    Possibly the reason is if there is 480v secondary at the road, the primary is likely 13,200v. Maybe they do not allow that high of a primary voltage to be run to transformers for dwellings.

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