I've read and found some good info here. My question is about adding a feeder to a new structure with its own sub-panel.
My main electrical panel is 200 amp and already has a 100 amp breaker that feeds a separate sub-panel in my workshop. This area is connected to the house. Plus the main panel has all the various breakers in it for the house.
Now I'm building a detached garage and want to but a 60 amp panel in it. The main panel physically has room in it. But what are the rules about how much or how many feeders the main panel will support?

 

No rules but common sense and perhaps a load calculation. Unless you have a heavy load in the attached garage you might consider feeding it from there if that panel is closer.

 

There is no limit on the number of subpanel feeders. The only real limitation is that a subpanel feeder leaving a panel cannot be larger than the incoming feed to that panel. Also not specific to feeders, but panels have a "max stab" rating which restricts large breakers from being installed directly across from one another where they share a bus fin; but other slots in the panel are acceptable. Ultimately the factor in determining if an electrical service is adequate is a "demand load calculation", which looks at what appliances, motors, lighting and other loads you expect to power from the service. If you're not adding any significant load (electric heat, spa, large machinery) in the garage there would be no need to look at increasing the service.

Based on your location and my assumption that you have gas heat, it is very unlikely that the 200A main service would be insufficient to support a detached garage.

 

Thank you gentlemen. I'm not planning any major electrical needs in the new garage. It is more for storage, the existing workshop has the welder and other bigger draws in it.