Thanks for your reply.
In order to answer your questions about my comments let me first elaborate on the design of my power system.
The way I have configured the system is as follows; power from the utility company goes to the main load center, then the automatic transfer switch (ATS), then the generator load center. The main load center is NOT powered during utility power failure.
During the loss of utility power the generator, via ATS logic, powers the generator load center, which provides power to all the high-priority circuits. Additionally, the generator load center provides power to the air-conditioning and the 90 amp sub-panel.
Dry contactors (terminals A-A) on the ATS allow the air-conditioning contactors to close when the ATS logic determines adequate power is available. The same is true for the dry contactors (terminals B-B ), which allows power to close a 90 amp, 2-pole, general purpose relay, providing power from the generator load center to the 90 amp sub-panel.
Regarding your question about balancing the load; the generator provides 240 volts via two legs at 120 volts each. Although the generator is capable of providing a total of 100 amps, it can only provide 50 amps per leg. My goal is to provide the maximum current from the generator by placing equal loads (within reasonable variations by trial and error) on each leg.
Regarding your question about my comment’ “as much stuff on the 90 amp sub panel.” Under no circumstance do I wan to overload the generator by placing too much on the generator load center, so I will attempt to maintain its load below the maximum threshold.
Don’t let the 90 amp sub-panel fool you into thinking it is part of the power limit. It is used because it is a convenient size for the number of circuits (spaces) required.
Now, the ATS logic will prevent overloading the generator by opening the contactors to the air-conditioning contactor and the 90 amp sub-panel contactor. My goal here is to put as much on the generator load center and the 90 amp sub-panel without opening the ATS contactor to the 90 amp sub-panel.
For example, say the generator load center requirement is 50 amps and the 90 amp sub-panel requirement is 50 amps, for a total of 100 amps. In theory, the generator will power both panels, if neither leg exceeds 50 amps. If one leg exceeds the 50 amp limitation I loose the entire 90 amp sub-panel.