Why would a central vacuum breaker trip once every time I used it?
It is likely your breaker type...

The CVS Power Unit is engineered using a high-performance motor. As with all power units, it is recommended
that the CVSPU have a dedicated circuit to ensure consistent operation.

ISSUE: Standard Square D Circuit Breakers May Cause Tripping
Several dealers have reported nuisance tripping issues with the CVSPU.
We have discovered that the some circuit breakers trip more easily when used to power the CVSPU. 
In discussions with a circuit breaker manufacturer, we were advised these breakers are not designed to operate high-performance appliances like
central vacuums, air compressors and even some microwave ovens. 

SOLUTION: Use High-Magnetic Breakers to Power CVSPU’s
The manufacturer recommends using high-magnetic designed breakers like those listed below for dedicated circuits
connecting to high-performance equipment. High-magnetic breakers can tolerate the high in-rush of current that occurs when high-
performance appliances start, preventing nuisance tripping.

Please be aware that if you experience nuisance tripping with the CVSPU, replacing the breaker should eliminate the issue. For new
construction, however, it would be preferable to discuss this issue ahead of time with the builder or electrician.

Recommended Breakers
The recommended breakers to use with the CVSPU are listed below:
• Square D (#QO115HM) for a 15 amp circuit
• Square D (#QO120HM) for a 20 amp circuit
• Square D Homeline (#HOM120HM) for a 20 amp circuit
These breakers are available where electrical supplies are sold.