A 15A circuit contains only a central vac unit, and an exterior floodlight and outlet. This breaker is tripping several times a week...always when nothing on the circuit is running or turned on. I replaced the breaker - no luck. The exterior junction boxes are dry. This began occurring suddenly 2 weeks ago, and had never occurred before. There has been no work to this circuit recently. I'm stumped, and would really appreciate any ideas. Thanks.