First I would check the electrical connections to the compressor and the breaker in the panel, see that they are tight and not corroded. Next I would measure the starting current of the compressor with a clamp on ammeter. I had a problem like this on a friends AC, only his problem was tripping the breaker at times. His compressor is about 10 years old, and is harder to start now. When I measured the starting current it measured 175 Amps! Which on this compressor is the locked rotor current! We replaced the starting capacitor and added a "Hard start kit". Now the starting current is a respectable 50 Amps.
Some tech info:
The induction type motors used in these compressors have an extra motor winding. This is called a "start" winding and is used with the "start capacitor" it is there only to get the motor to initially turn and a mechanical switch disengages it at a low speed. What happens over time is that the motor load is increased due to wear, and the start capacitance becomes weaker. So why not just build a compressor with a large start up capacitance to begin with? Some higher end units do just that, but most don't to save $$$. Contrary to popular belief, the start capacitor size does not "Give a bigger jolt" to the motor, but delays the 60 cycle feed to the second winding fooling the motor to think it is driven by a poly phase feed. The larger the capacitor value, the bigger the delay - hence the lower the starting current. Without a start winding, the motor will sit there humming until it trips the breaker. Three phase motors (poly phase) do not have start windings because they have three windings.
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.
Best Answer
If a breaker is tripping regularly, that's a serious problem you should look at. That is not normal or acceptable. It means something is wrong with your overcurrent protection, or a defective device actually drawing too much current.
It is normal for circuit breakers to allow overcurrent for a short amount of time. This is needed by motors to start, incandescent bulbs to light, and many electronic power supplies to initially start up. The term is called "inrush current".
Ultimately the purpose of breakers is to protect wiring and receptacles. Overcurrent makes them excessively warm, but small overcurrent makes them warm slowly. The breaker is designed to trip before this heat would endanger the wires.
Many breakers also have an instantaneous trip, where they will trip immediately for very high current (i.e. a dead short). This is many times the nameplate rating of the breaker.
There is a chart for your breaker of how much overcurrent it will permit for how long. Here is one example, there should be a vaguely similar chart for your breaker. I'd get and see if it explains your breaker's tripping behavior. If it doesn't, then either your measuring method is not precise enough, or you have a bad breaker. I would be surprised at a breaker instantaneously tripping at 125% of rating.