7.8 Inspection and Cleaning NFPA 70B – 17.8
Insulated-case and molded-case circuit breakers should be kept clean of external contamination so that internal heat can be dissipated in a normal manner.
Note: A clean case reduces a possible arcing condition between exposed live conductors and between energized conductors and ground.
The structural strength of the case is important in withstanding the stresses during fault-current conditions. Naturally, the case should be inspected for cracks and replaced where necessary.
Loose Connections NFPA 70B – 17.9
Excessive heat in a circuit breaker can cause a nuisance tripping and possibly lead to a failure. Loose connections are the most common cause of excessive heat. Maintenance inspections for loose connections or evidence of overheating should be checked as deemed as necessary. Tightness of loose connections should be performed and comply with NFPA 70B – 8.11. Insulated-case and molded case circuit breakers having non-interchangeable trip units are appropriately adjusted, tightened, and sealed at the factory. Interchangeable trip units installed and maintain improperly may overheat if not tightened properly during installation. Manufacturer’s recommended maintenance procedures of connections should be followed.