The Safe Current-carrying Capacity of Common Cables

The following are the safe current-carrying capacities and selection methods of common cables, covering copper-core and

aluminum-core cables, and accompanied by estimation formulas and influencing factors: I. Table of Safe Current-carrying Capacities of Common Cables 1. Copper-core Cables (Exposed Installation, Ambient Temperature 25℃)

2. Aluminum-core Cables (Exposed Installation, Ambient Temperature 25℃)

II. Estimation Formula for Current-carrying Capacity (Based on Aluminum-core Insulated Wires) Formula: "Five times for below 10, twice for above 100. For 25 and 35, it's between four times and three times. For 70 and 95, it's two

and a half times. For pipe installation and high temperature, it's 80% or 90% of the original value. For copper wires, calculate

according to the next larger size of aluminum wires." Explanation: 1. **Five times for below 10**: For aluminum wires with a cross-sectional area of 10mm² and below, the current-carrying

capacity is **5 times** the cross-sectional area (for example, for a 2.5mm² aluminum wire: 2.5×5 = 12.5A, and the actual value

is taken as 12A).

YouTube：https://youtube.com/shorts/3FHF0FqZfhU  2. **Twice for above 100**: For aluminum wires with a cross-sectional area of more than 100mm², the current-carrying capacity

is **2 times** the cross-sectional area. 3. **For 25 and 35, it's between four times and three times**: For a 25mm² aluminum wire, calculate it as **4 times** (25×4 = 100A),

and for a 35mm² aluminum wire, calculate it as **3 times** (35×3 = 105A). 4. **For 70 and 95, it's two and a half times**: For 70mm² and 95mm² aluminum wires, calculate them as **2.5 times** (for example,

70×2.5 = 175A). 5. **For pipe installation and high temperature, it's 80% or 90% of the original value**:   - For pipe installation, the current-carrying capacity is **80%** of the original value. If the ambient temperature is > 25℃, it's *

*90%** of the original value. If both situations exist, it's **70%** of the original value. 6. **For copper wires, calculate according to the next larger size of aluminum wires**: The current-carrying capacity of copper wires

is calculated according to the **next larger size of aluminum wires** (for example, a 4mm² copper wire is approximately equal to a

6mm² aluminum wire: 6×7 = 42A). III. Key Factors Affecting the Current-carrying Capacity 1. **Ambient Temperature**:   - For every 10℃ increase in temperature, the current-carrying capacity decreases by approximately **10%~15%** (for example,

when the temperature is 25℃, the current-carrying capacity of a 2.5mm² copper wire is 26A, and when the temperature is 35℃,

it's about 23A). 2. **Laying Method**:   - For pipe installation (steel pipe/plastic pipe): The current-carrying capacity is **80%** of the original value.   - For multiple wires laid in parallel: For each additional wire, the current-carrying capacity decreases by **10%~20%** (for example,

if there are 3 wires in the same pipe, it's **70%** of the original value). 3. **Insulation Material**:   - Polyvinyl Chloride (PVC) insulation can withstand a temperature of **70℃**, and Cross-linked Polyethylene (YJV) insulation can

withstand a temperature of **90℃**. The latter has a higher current-carrying capacity. IV. Selection Suggestions for Common Household Scenarios

V. Safety Precautions 1. **Avoid Overload**: The actual current should be **≤80% of the current-carrying capacity** (leave a margin). 2. **Neutral Wire Specification**: In a single-phase circuit, the specification of the neutral wire is **the same as that of the phase wire**.

In a three-phase circuit, the neutral wire is ≥ **1/2 of the phase wire**. 3. **Professional Verification**: For complex circuits (such as industrial power supply), the formula **\(I = P / (\sqrt{3}U\cosφ)\)**

needs to be used for calculation, or refer to national standards (such as GB/T 12706). **Example**: When installing 2 air conditioners of 1.5 horsepower at home (the power of a single unit is 1.1kW, and the total power is 2.2kW),

the total current \(I = 2200W/220V = 10A\). Selecting a **2.5mm² copper-core wire** (the current-carrying capacity for pipe

installation is 20A) is sufficient.