Use this calculator to determine the indicative copper and aluminum wire sizes (AWG ) wire size for single phase AC applications. To obtain the wire gauge, you need to provide the following information to the calculator:

- the supply voltage (V)
- load current (A)
- one-way length of cable (feet)

**Note:** This information is a guide. You should still consult a professional when designing your AC application.

**Note:**

- Wire length used is the one way length of wire from the voltage source to the appliance
- Resistance values used in the calculator are based on alternating-current resistance values for 600-Volt Cables, 3-Phase, 60 Hz, 75°C (167°F) — Three Single Conductors in Conduit.
- Resistance values assume a fully loaded conductor at that temperature. Resistance for conductors hence voltage drop at different temperatures, stranding may vary.

**Worked example** **using the calculator – calculating voltage drops**

*What is the voltage drop for 4 gauge wire, carrying 15 amps over 200 feet at 120 V?*

Using the calculator, the voltage drop is 2% with a final voltage of 117.6V.

### Formula for calculating AC Voltage drop

The AC voltage drop for single phase can be found from the formula = **I*R** where:

- I is the alternating current flowing
- R is the alternating current resistance for the conductor based on NEC Table 9.

### Why you should minimize voltage drops

Voltage drops results in wasted power along the cable run and a reduced voltage for the appliance which may cause the appliance not to work properly.

To ensure that your appliance receives its *recommended minimum operating voltage, *always select a wire gauge for the cable length such that the final voltage for the appliance **meets your appliance voltage requirements** (ideally not more than 3% for branch circuits).

### 2 Effective ways of minimizing voltage drops

**# 1. Avoid unnecessary long cable runs**

For example, at 120V, an appliance drawing 10A over 10 AWG wire with the one way cable length to the appliance at 90 feet results in a voltage drop of about 2%.

Should this distance double (180 feet), then the voltage drop increases to 4% resulting in more power wastage and possibly the appliance may not work properly.

**Fix:** To maintain the voltage drop (2%) while maintaining the cable length, decrease the wire gauge to 6 AWG.

**# 2. For appliances with a high power consumption, use a lower AWG (thicker wire)**

Larger appliances (larger loads) require more current which results in a bigger voltage drop for the same distance. Therefore to reduce the drop, you need to increase the size of wire, lower gauge.

For example, at 120V, you have 3% voltage drop when powering an appliance that draws 10A load over 12 AWG wire at a one way distance for the load of 70ft.

If a larger appliance (draws more current) is connected drawing 15A as an example, to maintain the same wire gauge and 2% voltage drop, one way cable should be 61 feet.

**Fix:**

- If this is not possible to move the load (reduce the cable length, you may use a thicker cable, 10AWG.
- Double the voltage to 240V if the load can take it which would allow you to extend the load up to 123 feet!

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