Mike Dolt Enterprises
Mike Dolt Enterprises
User: mphillipps, Location: Dallas, Tx
Asked on: Friday, April 1, 2011 at 2:10 pm EDT
Answered on: Tuesday, May 14, 2024 at 3:37 am EDT
Question: I've been invited to bid on a project with a installing a new 50 amp sub panel 250' away from the service entrance. My VD calculation is at 3.2 %.Do I need to adjust the awg to correct to >3% ?
Yes, you need to adjust the AWG to correct to >3%.
Voltage Drop Calculation
Voltage drop (VD) is calculated using the following formula:VD = (Cable Length) x (Current) x (Resistance per Unit Length)
Adjusting AWG
If the VD calculation exceeds 3%, you need to reduce the resistance per unit length by increasing the AWG (wire gauge). A larger AWG wire has a lower resistance than a smaller AWG wire.To determine the appropriate AWG, refer to the National Electrical Code (NEC) Table 310.16. Find the maximum allowable VD for your project (typically 3%) and the amperage you need to carry (50 amps).For a 250' run and 50 amps, you will likely need to use a
#4 AWG copper wire to achieve a VD of less than 3%.
Important Note:
The NEC also sets minimum AWG requirements for certain applications. Ensure that your chosen AWG meets the minimum requirement for the subpanel installation. Flag for review