Voltage Drop. Calculated Industries ElectriCalc Pro 5060, ElectriCalc Pro

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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

([Length]) 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 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 is sufficient to meet safety standards.

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IMPORTANT NOTE ON

VOLTAGE DROP CALCULATIONS

The ElectriCalc Pro calculates voltage drop and wire size using DC resistance as defined by the 2002 NEC. To find the voltage drop for a specific wire size, you must first enter amps and the oneway wire length (and other required variables), entering the specific wire size last. Otherwise, for your safety the calculator will recalculate the wire sizes based on the ‘99 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?

Steps Keystrokes Display

Reset calculator [Set] [x] [On/C]

Set to 1-phase

Set to 75°C

[Set] [1]

0.

1 PH

[Set] [7] 1Ø 75 Cu 1 PH

Enter amps

Enter volts

Enter length

Enter wire size

11 [Amps]

208 [Volts]

175 [Length]

8 [WireSz]

11. AMPS

208. VOLT

175. FEET

8 CU

Solve volt. drop

Solve % v.drop

[VD%]

[VD%]

AWG WIRE SIZE

3.0 DROP V

1.4 DROP V %

User’s Guide — 43

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Finding Three-Phase

Voltage Drop

A 20-amp three-phase load is being fed by a 230-volt source located 150 feet away. The installation specifications require 75°C #10 THW stranded copper conduc-tor. What is the voltage drop on this branch circuit?

Steps Keystrokes Display

Reset calculator [Set] [x] [On/C]

Set to 75°C

Enter amps

[Set] [7]

20 [Amps]

0.

3Ø 75 Cu 0.

20. AMPS

Enter volts 230 [Volts]

Enter length(feet) 150 [Length]

Enter VD wire size10 [WireSz]

230. VOLT

150. FEET

10 CU

Solve volt. drop

Solve % v.drop

[VD%]

[VD%]

AWG WIRE SIZE

6.4 DROP V

2.8 DROP V %

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Finding Voltage Drop Wire Size

A 20-amp single-phase 208-volt load will be located 175 feet away from the source. Assuming a 3% allowable voltage drop, what is the size of 75°C conductor re-quired for this branch circuit?

Steps Keystrokes Display

Reset calculator [On/C]

Set to 75°C [Set] [7]

Set to 1-phase

Enter amps

Enter volts

[Set] [1]

20 [Amps]

208 [Volts]

0.

3Ø 75 Cu 0.

1 PH

20. AMPS

208. VOLT

Enter distance 175 [Length]

Enter allow. VD% 3 [VD%]

Find wire size [WireSz]

175. FEET

3.0 DROP V %

8 CU

AWG VD WIRE SIZE

Find actual voltage drop

Find % v.drop

[VD%]

[VD%]

5.4 DROP V

2.6 DROP V %

User’s Guide — 45

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Finding Voltage Drop Distance

How far from a single-phase 240-volt source can you install a 15 amp load using 60°C #10 Al branch circuit conductors? Assume a 3% allowable voltage drop.

Steps Keystrokes Display

Reset calculator [Set] [x] [On/C]

Set to 1-phase [Set] [1]

Set to aluminum [Set] [4] 1Ø 60 Al 1 PH

Enter amps 15 [Amps] 15. AMPS

Enter volts 240 [Volts] 240. VOLT

Enter wire size

0.

1 PH

Enter 3% VD

Find distance

Find actual

10 [WireSz] 10 AL

AWG WIRE SIZE

3 [VD%] 3.0 DROP V %

[Length] 123.77387 FEET voltage drop

Find % v.drop

[VD%] 7.2 DROP AL V

[VD%] 3.0 DROP AL V %

NOTE: The calculator automatically makes adjustments for resistance using

NEC Chap 9, Table 8, if the insulation type is other than 75°C.

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Finding Voltage Drop

Resistance

What is the resistance of 85 feet of #2

90°C copper conductor?

Steps Keystrokes Display

Reset calculator [Set] [x] [On/C]

Set to 90°C mode [Set] [9]

0.

3Ø 90 Cu 0.

Enter wire size

Find resistance

2 [WireSz] 2 CU

AWG WIRE SIZE

[Set] [Length] 0.2033993

OHMS WIRE

Find 85 ft resist* [÷] 1000 [x] 85 [=] 0.0172889

*NOTE: Given resistance per 1000 feet, divide by 1000 to get a per foot resistance, then multiply by 85.

Finding DC Resistance

What is the equivalent resistance of a

12 volt DC circuit pulling 5 amps?

Steps Keystrokes

Reset calculator [On/C]

Enter voltage

Enter amps

Find resistance

12 [Volts]

5 [Amps]

[Set] [Volts]

Display

0.

12. VOLT

5. AMPS

2.4 OHMS

User’s Guide — 47