Cable size by load calculator: Checking load and wire-size candidates — Worked Scenario

What this scenario actually checks

Select the installation country before calculating: South Korea uses KEC-referenced KS tables and the USA uses NEC 2023 reference conditions. Korean sizes use mm²; US sizes use AWG or kcmil. Enter essential values first, then expand installation conditions and calculation details when needed.

This walkthrough focuses on checking load and wire-size candidates. It follows the published tool inputs, not a new formula or an automatically verified legal, financial, medical or engineering determination.

Start by preparing the right inputs

Choose the installation country independently of the display language. Korea KEC/KS and USA NEC 2023 are separate profiles; verify the locally adopted NEC edition. Enter load power, supply and installation method. A supported general-wiring breaker rating and cable size candidate are selected automatically. Expand Site conditions to adjust temperature, grouping or power factor, or to enter a verified breaker rating manually.

Before copying the example, confirm that each entered unit, date, dimension and default matches your real task. Changing only a visible number without revisiting its assumptions can change what the answer means.

• Choose the installation country independently of the display language. Korea KEC/KS and USA NEC 2023 are separate profiles; verify the locally adopted NEC edition.
• Enter load power, supply and installation method. A supported general-wiring breaker rating and cable size candidate are selected automatically. Expand Site conditions to adjust temperature, grouping or power factor, or to enter a verified breaker rating manually.
• Read the concise result, or expand Calculation details for correction factors and conditions. Voltage drop, protection coordination, equipment and manufacturer limits require separate verification.

Worked example with the calculator

Use the following input values: Korea · 10 kW electrical input, 380 V three-phase, PF 0.9, copper XLPE B2, 30°C, 1 circuit, automatic breaker.

The example output is Breaker candidate 20 A; cable 2.5 mm²; allowable ampacity 26 A. Load current is about 16.88 A. Select the supported 20 A rating, then the smallest cable rated at least 20 A under these conditions. Special loads need separate protection selection.

Treat this as a reproducible example, not a result to reuse with different measurements.

What can change the answer

Read the concise result, or expand Calculation details for correction factors and conditions. Voltage drop, protection coordination, equipment and manufacturer limits require separate verification. Korea supports copper B2/C 1.5–300 mm². USA supports copper THHN/THWN-2 90°C, 14 AWG–500 kcmil under raceway/cable conditions, with a 60°C termination default, optional verified 75°C terminations, small-wire OCP caps and the selected 125% continuous-load allowance.

Is ampacity alone enough to select a cable? No. This page suggests a cable and breaker under the selected assumptions. Real designs must also review voltage drop, protection coordination, site conditions and manufacturer data.

Before using the result for a real decision

For checking load and wire-size candidates, check the original measurements and input units, and save the assumptions alongside any number you share.

Where legal rules, official allowances, equipment ratings or contractual conditions matter, consult their current authoritative documents. An illustrative estimate is not a substitute for that verification.

• Reproduce the example before changing inputs
• Check all units and assumptions, including any default values
• Verify official or manufacturer-specific requirements outside the calculator