Transfer Switch for Generator

[raywu1688]

Just joined as DIY homeowner.
I plan on buying a 10KW backup portable generator and using a transfer switch on the house in Riverside County. As part of that plan, I have these questions on transfer switch configuration that will pass inspection to get a permit. It is a chicken and egg situation for me to know what the county allows before doing anything:

The transfer switch (TS) in question is a 50A 10-circuit transfer switch. Position A&B jointly is a double-pole 30A breaker, the rest are 20A breaker. I'll focus on A&B. This transfer switch already has a built-in 50A power inlet for a generator 50A cable.

Questions

1) My outdoor 150A main panel has a 100A (child) breaker servicing an indoor Subpanel. The subpanel has individual 20A and lower amperage breakers. Can myTS's 30A breaker (A&B positions) be the counterpart/service of that 100A breaker, given that I will/can pick and choose which breaker in the subpanel to be active, this would enable me to limit usage to 30A?
For example, I will only turn on a 20A and a 10A breaker on the subpanel in a power outage. For this example, that would mean the Transfer Switch is only servicing a 20+10A breakers of the subpanel using its A&B 30A breaker. My thought was that if the user wrongly activates Subpanel's 20+10+10A, then the TS 30A will trip, upon tripping none of the wire gauge would overheat. Then I would realize to turn off one of the breakers on the Subpanel back down to 30A only, and all would be good.

 

[davesparks]

Switching on a 20A breaker doesn't cause 20A to flow in a circuit, it makes the circuit live and allows up to 20A to flow if something is connected which draws that much.

So in your scenario turning on a 20A and 2x 10A breakers won't cause the 30A breaker to trip unless those 3 breakers are fully loaded.

 

[raywu1688]

Switching on a 20A breaker doesn't cause 20A to flow in a circuit, it makes the circuit live and allows up to 20A to flow if something is connected which draws that much.

So in your scenario turning on a 20A and 2x 10A breakers won't cause the 30A breaker to trip unless those 3 breakers are fully loaded.

I knew that (your answer), one sized a breaker based on max current the wire gauge will handle. Your answer did not answer my original posted question: Can the transfer switch 30A be servicing the 100A of the 150A main panel? That 100A service indoor subpanel with multiple 20A and lower breakers. I do not intend to activate more than 30A on that subpanel. I know technically that can-do and even work as planned, but is that (California) code compliant is the motive of my question. If not code complaint and there is really no fusible transfer switch out there that has a breaker with 100A capacity, what could i do?