Application planning
5.7 Use in unusual environments:
3VL IEC molded case circuit breakers
System Manual, 11/2013, 110 0110 - 02 DS 03
67
Use in unusual environments:
If the 3VL molded case circuit breakers are to be used outside closed control cabinets or in
difficult operating conditions, the following information must be taken into account at the
planning stage:
Reduction factors under unusual operating conditions
● Altitude in excess of 2000 meters
● Temperature above 50 °C
● Frequencies outside the 50 / 60 Hz range
● Humidity
● etc.
You can find further details in DIN ISO 2533 "Standard Atmosphere".
Use at altitudes above 2,000 meters
The lower air density at altitudes above 2,000 meters affects the key electrical data of
molded case circuit breakers. The table in the Technical data (Page 142) shows the derating
factors that have to be taken into account when using the molded case circuit breakers at
altitudes above 2,000 m.
Use at different ambient temperatures
A reduction (derating) of the rated operational current of the 3VL molded case circuit
breakers is necessary if the ambient temperature around the molded case circuit breaker
exceeds 50 °C. The reference temperature is 40 °C for molded case circuit breakers with
RCD modules or for plug-in / withdrawable versions.
The permissible load for various ambient temperatures with reference to the rated
operational current of the molded case circuit breaker are shown in the technical data.
Furthermore, the following points must be taken into consideration, because each one of
these factors can influence the rated operational current and permissible load.
● Type of molded case circuit breaker (fixed-mounted, plug-in or withdrawable version)
● Type of main connection (vertical/horizontal busbar, cable)
● Ambient temperature around the molded case circuit breaker
● Altitude derating factors
● Temperature derating factors based on different trip units and connections
● Increased degree of protection
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