Wire Size worksheet

1. Suggested size (planning estimate): 6 AWG aluminum

1. Find the smallest size the table allows for 50 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{6 AWG}$

2. Work out the resistance of 6 AWG wire over the run. Current travels out and back, so double the one-way length

   $2\times 54.86\times 0.00212$$=0.2326\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.2326\times 50$$=11.631\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{11.631}{480}$$=\mathrm{2.42\%}$

5. Current sets the size here. Voltage drop is already within your limit.

   $\text{planning estimate}$$=\text{6 AWG aluminum}$

2. Suggested size (planning estimate): 3/0 AWG copper

1. Find the smallest size the table allows for 30 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{10 AWG}$

2. Work out the resistance of 3/0 AWG wire over the run. Three-phase circuits use √3 times the one-way length

   $1.732\times 39.62\times 0.000203$$=0.0139\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.0139\times 30$$=0.417\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{0.417}{24}$$=\mathrm{1.74\%}$

5. Voltage drop sets the size here. 10 AWG could carry the current, but it would lose 28.11%.

   $\text{planning estimate}$$=\text{3/0 AWG copper}$

3. Suggested size (planning estimate): 8 AWG copper

1. Find the smallest size the table allows for 50 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{8 AWG}$

2. Work out the resistance of 8 AWG wire over the run. Current travels out and back, so double the one-way length

   $2\times 42.67\times 0.002061$$=0.1759\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.1759\times 50$$=8.794\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{8.794}{277}$$=\mathrm{3.17\%}$

5. Current sets the size here. Voltage drop is already within your limit.

   $\text{planning estimate}$$=\text{8 AWG copper}$

4. Suggested size (planning estimate): 4 AWG copper

1. Find the smallest size the table allows for 20 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{12 AWG}$

2. Work out the resistance of 4 AWG wire over the run. Three-phase circuits use √3 times the one-way length

   $1.732\times 36.58\times 0.000815$$=0.0516\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.0516\times 20$$=1.033\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{1.033}{48}$$=\mathrm{2.15\%}$

5. Voltage drop sets the size here. 12 AWG could carry the current, but it would lose 13.75%.

   $\text{planning estimate}$$=\text{4 AWG copper}$

5. Suggested size (planning estimate): 10 AWG copper

1. Find the smallest size the table allows for 15 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{14 AWG}$

2. Work out the resistance of 10 AWG wire over the run. Current travels out and back, so double the one-way length

   $2\times 54.86\times 0.003277$$=0.3596\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.3596\times 15$$=5.393\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{5.393}{208}$$=\mathrm{2.59\%}$

5. Voltage drop sets the size here. 14 AWG could carry the current, but it would lose 6.56%.

   $\text{planning estimate}$$=\text{10 AWG copper}$

6. Suggested size (planning estimate): 3 AWG copper

1. Find the smallest size the table allows for 100 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{3 AWG}$

2. Work out the resistance of 3 AWG wire over the run. Three-phase circuits use √3 times the one-way length

   $1.732\times 60.96\times 0.000646$$=0.0683\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.0683\times 100$$=6.825\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{6.825}{480}$$=\mathrm{1.42\%}$

5. Current sets the size here. Voltage drop is already within your limit.

   $\text{planning estimate}$$=\text{3 AWG copper}$

7. Suggested size (planning estimate): 10 AWG copper

1. Find the smallest size the table allows for 30 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{10 AWG}$

2. Work out the resistance of 10 AWG wire over the run. Three-phase circuits use √3 times the one-way length

   $1.732\times 57.91\times 0.003277$$=0.3287\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.3287\times 30$$=9.861\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{9.861}{480}$$=\mathrm{2.05\%}$

5. Current sets the size here. Voltage drop is already within your limit.

   $\text{planning estimate}$$=\text{10 AWG copper}$

8. Suggested size (planning estimate): 12 AWG aluminum

1. Find the smallest size the table allows for 15 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{12 AWG}$

2. Work out the resistance of 12 AWG wire over the run. Current travels out and back, so double the one-way length

   $2\times 42.67\times 0.008523$$=0.7274\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.7274\times 15$$=10.911\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{10.911}{277}$$=\mathrm{3.94\%}$

5. Current sets the size here. Voltage drop is already within your limit.

   $\text{planning estimate}$$=\text{12 AWG aluminum}$

9. Suggested size (planning estimate): 4 AWG copper

1. Find the smallest size the table allows for 60 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{6 AWG}$

2. Work out the resistance of 4 AWG wire over the run. Current travels out and back, so double the one-way length

   $2\times 31.7\times 0.000815$$=0.0517\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.0517\times 60$$=3.101\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{3.101}{208}$$=\mathrm{1.49\%}$

5. Voltage drop sets the size here. 6 AWG could carry the current, but it would lose 2.37%.

   $\text{planning estimate}$$=\text{4 AWG copper}$

10. Suggested size (planning estimate): 10 AWG aluminum

1. Find the smallest size the table allows for 15 A, using the 75 °C column and the limits for small wires

   $\text{sized for current}$$=\text{12 AWG}$

2. Work out the resistance of 10 AWG wire over the run. Current travels out and back, so double the one-way length

   $2\times 45.72\times 0.00536$$=0.4901\text{\hspace{0.17em}Ω}$

3. Multiply by the current to get the voltage lost in the wire

   $0.4901\times 15$$=7.352\text{\hspace{0.17em}V}$

4. Compare that loss with your source voltage to see the percent drop

   $\frac{7.352}{208}$$=\mathrm{3.53\%}$

5. Voltage drop sets the size here. 12 AWG could carry the current, but it would lose 5.62%.

   $\text{planning estimate}$$=\text{10 AWG aluminum}$