Masterpact and Powerpact circuit breakersResolution:
Masterpact and Powerpact P and R breakers which have gotten wet are prone to nuisance tripping. Water will interfere with normal operation of the current sensors, reporting more current to the trip unit than actually exists, resulting in tripping with Ir, Ii, Ig, Ap indication, or no indication. Which function trips depends on the magnitude of phantom current reported to the trip unit. It is also possible for water to compromise the trip unit causing nuisance tripping.
Once a circuit breaker has become wet enough to nuisance trip, it cannot be restored to reliable operation and the recommendation of NEMA and of Schneider Electric is to replace the breaker.
Links to bulletins:static.schneider-electric.us/docs/Circuit%20Protection/0110DB0401.pdf