[ChasenSmokey]

I have an existing 200 amp service with an existing 100 amp sub-panel for a generator. See attached picture. I am wanting to add another 100 amp double pole breaker within the existing main panel to supply a new 100 amp box within a detached garage located approximately 200' away. All of the breakers inside the existing main panel are already of the "mini" type. The breakers in the 100 amp sub-panel for the generator are of the "standard" type. I do not have a generator. Can I move some breakers out of the main panel and put them in the sub-panel for the generator freeing up room within the main panel to add another 100 amp breaker?

 

[Syberia]

Yes. If the panels are not the same brand, you may have to buy new breakers, but I'm assuming you knew that.

 

[ChasenSmokey]

I am worried about overloading the panel. Is there a limit to how many sub panels that one can have off of a main panel

 

[Oso954]

There is no way for us to tell you whether it will overload the main. We have no way to tell how lightly or heavily your circuits are loaded.
You need to do a load calc, or get someone to do it for you.

 

[MrElectricianTV]

I have an existing 200 amp service with an existing 100 amp sub-panel for a generator. See attached picture. I am wanting to add another 100 amp double pole breaker within the existing main panel to supply a new 100 amp box within a detached garage located approximately 200' away. All of the breakers inside the existing main panel are already of the "mini" type. The breakers in the 100 amp sub-panel for the generator are of the "standard" type. I do not have a generator. Can I move some breakers out of the main panel and put them in the sub-panel for the generator freeing up room within the main panel to add another 100 amp breaker?

The labeling inside of the panels will tell you the maximum thin circuit breakers that can be installed. Sometimes the model number of the panel offers a clue such as 3040 or 1224. They interpret to a 30 space, 40 circuit panel or a 12 space, 24 circuit panel. If your panel is not approved for thin circuit breakers you cannot install them.

 

[Plumbvoltage]

Is there a limit to how many sub panels that one can have off of a main panel

I don't believe there is a limit.
I have two subs off my main and a sub off one of my subs in my shop 200 amp service.