[RE-wrenches] DC wire sizing

[Warren Lauzon]

I would never design such a system. That is what MPPT controllers are for. 10 years ago we did not have that choice, but now we do, so there is no reason at all to design a 40 amp 12 volt array circuit.

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Northern Arizona Wind & Sun - Electricity From The Sun Since 1979
Solar Discussion Forum: http://www.wind-sun.com/ForumVB/
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  ----- Original Message ----- 
  From: Kent Osterberg 
  To: Wrenches 
  Sent: Saturday, April 10, 2010 9:22 AM
  Subject: [RE-wrenches] DC wire sizing


  Here's my challenge to all of you that want to design for 1% or 1.5% voltage drop all the time:
  Take a 50-ft circuit carrying 40 amps at 12 volts, going to a C40 charge controller, select your wire size for 1% or 1.5% loss. You know that's not a practical solution.  I know that it makes more sense to replace the charge controller and run the PV circuit at a higher voltage.

  At % loss did it become impractical?  Ray's answer and my answer is "when there is a cheaper alternative -- lower cost per watt out or lower cost per kWh over the project life."  And that answer works even when you are considering a 400-kW PV array that is 1000 feet away.

  Kent Osterberg
  Blue Mountain Solar, Inc.




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