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Thursday, July 20, 2017
Question:
Scenario: Need 150A of continuous loads 480ft away from an existing 200A 120/240v panel. If I were going to install / relocate a new panel / subpanel at the 480 ft distance, what size wire and OCPD would be required? What is the equation for figuring this out, and do I use the 120v or 240v for calculating voltage drop?
Thank you, Kenny
A
Answer:
Hey Kenny thanks for your question. Conductors and overcurrent devices must be sized at 125% of the load if it is a continuous load as stated in 215.2 and 215.3. Voltage drop limits are not generally required by the NEC but Informational Note No. 2 to 215.2(A)(1) indicates that 3 % for feeders and 5% for the total will provide a reasonable efficiency of operation. Energy codes and manufacturer's instructions can also have requirements. You use the voltage of the loads for doing calculations and here are some online tables and voltage drop calculators
http://www.cerrowire.com/voltage-drop-table
http://www.southwire.com/support/voltage-drop-calculator.htm
http://www.calculator.net/voltage-drop-calculator.html