Reference Ambient Air Temperature is one third (1/3) of sum of ( Maximum Current Air Temperature °C, Maximum Daily (24 hours) Average Air Temperature °C, Maximum Annual Average Air Temperature °C, +10°C ). As per IS 9676.
- Maximum Ambient Air Temperature °C : 45 °C
- Maximum Daily (24 hours) Average Air Temperature °C : 35 °C
- Maximum Annual Average Air Temperature °C : 30 °C
Electrical Equipments, Switchgear & ASSEMBLY, shall be rated to be used at stadnard reference Ambient Air Temperature of 40°C.
For conducting any Test on the ASSEMBLY / Switchgear, Ambient Air Temperature should be measured during last quarter (15 minutes before the Test), it can be computed by means of two or more thermometers or thermocouples equally distributed around the ASSEMBLY at half its height and at a distance of 1 meter from the ASSEMBLY. As per IEC 61439.
While computing the Ambient Air Temperature, the temperature measuring devices shall be protected against air currents and heat radiations.
Ambient Air Temperature for indoor installations
For Indoor Installations, Ambient Air Temperature does not exceed +40°C and its average over a period of 24 hours does not exceed +35°C.
For Indoor Installations, Relative humidity should not exceed 50% at a maximum temperature of +40°C. At lower temperature higher relative humidity many be allowed.
Ambient Air Temperature for outdoor installations
For outdoor Installations, Ambient Air Temperature does not exceed +40°C and its average over a period of 24 hours does not exceed +35°C.
For outdoor Installations, Relative humidity may exceed to 100% temporarily at maximum temperature of +25°C.