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.
.................................................................................................. Northern Arizona Wind & Sun - Electricity From The Sun Since 1979 Solar Discussion Forum: http://www.wind-sun.com/ForumVB/ .................................................................................................. ----- 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. ------------------------------------------------------------------------------ _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
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