Service and maintenance
10.2 Troubleshooting
3VL IEC molded case circuit breakers
128 System Manual, 11/2013, 110 0110 - 02 DS 03
Mechanical and
electrical functions:
High humidity The molded case circuit breakers must not be used in environments
with high humidity since this can cause dielectric and insulation
problems. In such environments, appropriate measures need to be
taken, such as placing the circuit breaker in an enclosure.
Corrosion The molded case circuit breakers are not designed to be used in
aggressive environments.
In such environments, the circuit breaker should be installed in a
Function of the internal
accessories
Determine what type of internal accessories are installed. Remove the
molded case circuit breaker cover and determine the type of
accessories using the circuit breaker order number. Then check for
correct functioning.
• Undervoltage release:
Ensure the correct voltage is connected to the undervoltage
release since otherwise, the circuit breaker cannot be tripped.
• Shunt release:
Ensure the voltage is not applied to the shunt release since this can
also prevent the circuit breaker from tripping.
• Auxiliary and alarm switches:
The auxiliary and alarm switches do not have any effect on the
protection function of the molded case circuit breaker.
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