Wire Temperature Rise Calculator

When current flows through a wire, resistance generates heat — and knowing how hot your wire gets is critical for safe electrical design. Enter your current, wire resistance, ambient temperature, and thermal resistance, then select your wire material and insulation type to get the conductor temperature and temperature rise. Secondary outputs include power dissipated, insulation max temperature, and the safety margin remaining before your insulation reaches its rated limit.

A

Current flowing through the wire

Ω

Resistance per unit length or total resistance

°C

Environmental temperature around the wire

°C/W

Thermal resistance from conductor to ambient

Results

Conductor Temperature

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Temperature Rise

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Power Dissipated

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Insulation Max Temperature

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Safety Margin

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Frequently Asked Questions

How do you calculate wire temperature rise?

Wire temperature rise is calculated using the formula: ΔT = I²R × Rth, where I is current, R is resistance, and Rth is thermal resistance. The total conductor temperature is ambient temperature plus the temperature rise.

What factors affect wire temperature rise?

The main factors are current flow (squared effect), wire resistance, thermal resistance to ambient, ambient temperature, wire material properties, and installation conditions like bundling or conduit.

How do I determine the thermal resistance of a wire?

Thermal resistance depends on wire size, insulation type, installation method, and ambient conditions. It's typically provided in manufacturer data sheets or can be estimated based on standard values for different wire types and installations.

What is the maximum safe operating temperature for different wire types?

Common limits are: PVC insulation (70°C), XLPE/EPR (90°C), PTFE (200°C), and Silicone (180°C). Always check manufacturer specifications and local electrical codes for specific requirements.

Why is current squared in the temperature rise calculation?

Power dissipation follows Ohm's law: P = I²R. Since temperature rise is proportional to power dissipated, doubling the current quadruples the temperature rise, making current the most critical factor.

How does ambient temperature affect wire capacity?

Higher ambient temperatures reduce the allowable current because the wire starts from a higher baseline temperature. Derating factors are applied in hot environments to maintain safe operating temperatures.

What safety margin should I maintain for wire temperature?

A safety margin of 10-20°C below the maximum rated temperature is recommended to account for variations in ambient conditions, load fluctuations, and aging effects on insulation.