Service and maintenance
10.1 Preventive measures
3VL IEC molded case circuit breakers
126 System Manual, 11/2013, 110 0110 - 02 DS 03
The following checks must be carried out within the scope of the inspection(s) and/or after
1,000 rated current shutdowns. Please proceed as follows:
● External circuit breaker housing
– Examine all visible surfaces for oxidation, residues or other adverse effects.
– Remove residues with a lint-free, dry and clean cloth. (Never use chemical cleaners or
water)
Damage to the molded case circuit breaker
Never carry out repairs to the plastic casing or the interior of the circuit breaker!
Molded case circuit breakers contain only maintenance-free components.
● Electrical and mechanical functions of the circuit breaker
– Test the operating lever to check the mechanical functioning of the molded case circuit
breaker contacts
● Function of the mechanical on and off switch
– Operate the trip button, if available. Return the molded case circuit breaker to the
starting position after each operation.
● Main circuits and control circuits, function.
● Check connections are tight
– Check the tightening torque of the connecting screws (80% of the tightening torque
recommended)
– Visual inspection of the incoming and outgoing cables
– Visual inspection of the connection accessories
– Replace damaged terminal accessories after cleaning the terminal area
● Check and, if necessary, correct the settings of the overcurrent release in accordance
with the system conditions
– Electronic molded case circuit breaker releases must only be tested with a device
especially supplied for this purpose (MLFB: 3VL9000-8AP01).
The operator (customer) must arrange for the disposal of the molded case circuit breaker or
the replaced parts at the end of their service life in accordance with the currently applicable
legal requirements and guidelines.
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