38 — electricalc
®
Pro
VOlTaGE DROP
The reduction in Voltage between the power source and the
load can be determined by entering the Phase, Volts, Amps,
Wire material, Voltage Drop Wire Size and Length of run.
The calculator determines Resistance and then the Voltage
reduction. Voltage Drop can be displayed as Volts dropped, or
as a percent reduction of potential load.
This calculator also finds Voltage Drop Wire Size once you
have entered or calculated the Phase, Volts, Amps, Length,
Wire Type, and allowable VD percentage. It will solve for the
distance () once you have entered or calculated the
Phase, Volts, Amps, Wire Type, Voltage Drop Wire Size, and
allowable VD percentage. The ElectriCalc Pro uses Resistance
values found in NEC Table 8 Chapter 9 to determine Voltage
Drop.
Note: Voltage Drop solutions may vary slightly from actual AC circuit
measurements, as the calculator does not incorporate factors such
as inductive reactance, skin effect, raceway material, etc. In most
situations, the DC Voltage Drop calculation method is sufcient to meet
safety standards for AC systems.
IMPORTANT NOTE ON VOLTAGE
DROP CALCULATIONS
The ElectriCalc Pro calculates Voltage Drop and Wire Size using DC
Resistance as dened by the 2011 NEC. To nd the Voltage Drop
for a specic Wire Size, you must rst enter Amps and the one-way
wire Length (and other required variables), entering the specic Wire
Size last. Otherwise, for your safety, the calculator will recalculate
the Wire Sizes based on the NEC Ampacity Tables and maximum
allowable Voltage Drop.
Finding Single-Phase Voltage Drop
You are installing 175 Feet of 75°C, #8 THW branch circuit Copper
conductors to supply an 11A load on a 208V 1Ø system. What is the
source Voltage Drop at the load?
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