Ambient conditions

Pollution degree

Operation of the 3VA1 and 3VA2 molded case circuit breakers is approved in accordance with IEC / EN 60947‑1 and IEC / EN 60664‑1 for pollution degree 3.

Ambient temperature

3VA molded case circuit breakers are used at ambient temperatures from -25 °C to +70 °C. Derating (reduction in rated operational current) is required at temperatures above +50 °C.
You will find more information on the applicable derating factors in chapter Derating and temperature compensation.

The permissible storage temperature in original Siemens packaging lies between -25 °C and +80 °C.

Special climatic requirements

3VA molded case circuit breakers including their accessories can also be used in challenging operating environments.

Harsh conditions of storage, transportation and stationary use

The molded case circuit breakers have been tested according to the relevant special test procedures defined in IEC / EN 60947‑1, Appendix Q for Class E applications.

This class covers the areas MC3 + CC2 + SC1:

  • Ambient temperature

  • Humidity

  • Vibration environment

  • Shock environment

These ambient conditions can be referred to as "Open deck, damp and cold atmosphere without salt spray" or "Difficult, non-marine conditions".

The following standards-related criteria are complied with:

  • IEC / EN 60068‑2‑2 "Bd" and IEC / EN 60068‑2‑1 "Ab":

    Temperature range: ‑25 °C … +70 °C

  • IEC / EN 60068‑2‑30 "Db"

    Humid heat up to +55 °C and air humidity up to 95 %

  • IEC / EN 60068‑2‑6 "Fc"

    Vibration test

  • IEC / EN 60068‑2‑27 "Ea"

    Shock resistance test

Between the tests of compliance with the standards and at the end of the tests, the usability of the devices is assured with the "Verification of operation characteristics".

Vibration resistance and shock resistance

3VA molded case circuit breakers are insensitive to vibrations and meet the requirements relating to mechanical and electromechanical vibration strength according to IEC / EN 60068 and the specifications of the shipbuilding societies.

The circuit breakers resist impacts of up to 10 g and are tested to withstand without damage their operating conditions with shock impact according to IEC / EN 60068‑2 27 "Ea" with 150 m/s² / 11 ms.

Installation altitudes

When 3VA1 and 3VA2 molded case circuit breakers are used at up to 2000 m above sea level, the rated data will not change.

An installation altitude above 2000 m can lead to higher temperatures at the switching devices. The lower density of air can significantly reduce heat dissipation,

making it necessary to decrease rated operational voltage, the rated uninterrupted current and the short-circuit values.

Refer to the table below for the calculation factor for determining the key values:



At maximum ambient temperature +50 °C


Thermal-magnetic trip units only