Temperature Standard for Air Switch in Distribution Box

Air switches in distribution boxes should operate within an ambient temperature range of -5°C to 40°C, with a 24-hour average not exceeding 35°C, according to IEC 62271-1 standards.

Standard Operating Temperature

For indoor medium-voltage and low-voltage equipment, including air switches in distribution boxes, the normal service ambient temperature is defined as follows:

• Maximum ambient temperature: 40°C
• Average over 24 hours: Not to exceed 35°C
• Minimum ambient temperatures: Commonly -5°C, -15°C, or -25°C depending on installation requirements . These limits ensure that the air switch operates reliably without overheating, insulation breakdown, or reduced mechanical performance.

Enclosure Considerations

The enclosure housing the air switch plays a critical role in maintaining safe operating temperatures:

• Ensure adequate ventilation or forced airflow to dissipate heat generated by the switch and connected conductors .
• The ambient temperature inside the enclosure should ideally be about 5 K lower than the maximum permissible temperature of the components .
• Avoid placing the distribution box in areas exposed to direct sunlight or excessive heat sources, as this can raise internal temperatures and reduce switch lifespan .
• For fully populated enclosures, consider fan-and-filter units to maintain airflow and prevent overheating .

Impact of Temperature on Air Switch Performance

• High ambient temperatures can reduce the current-carrying capacity of the air switch and may trigger nuisance tripping.
• Low temperatures can affect the mechanical operation of moving parts, especially in isolation or circuit-breaking mechanisms.
• Condensation and humidity, often associated with temperature fluctuations, can lead to corrosion or insulation failure, so proper enclosure design and climate control are recommended .

Practical Recommendations

• Verify the manufacturer's datasheet for the specific air switch model, as some devices may have narrower temperature ranges.
• Maintain clearances around the distribution box to allow natural convection or forced cooling.
• In high-temperature environments, consider derating the switch or using climate-controlled enclosures to ensure long-term reliability. By adhering to these temperature standards and enclosure practices, air switches in distribution boxes can operate safely, maintain their rated performance, and achieve a long service life.