Circuit breaker nuisance trips.
If the cicuit breaker trips occasionally, even when stat and floor test OK, it may be because of in-rush on large heating systems. If everything tests OK, try one of these:
QO-HID and QOB-HID High Intensity Discharge Circuit Breakers
These items are pretty expensive, but they are designed for HID lighting, and are designed for high in-rush applications.
Available locally, do a google search for locations.
If these do not remedy the situation, they may have electrical issues in the house.