Excuse my ignorance, but what is the advantage of installing a sub panel? The sub panel goes back to the main panel, correct? So is it just a way to avoid multiple pulls of you want multiple circuits? Or is it just a way to accommodate multiple breakers if you're out of room in your main box?
If I wanted add say, two 20A circuits in a sub panel, this would need to go back to a 40A breaker in the main box, correct? At some point you would exceed the max capacity of the main box, no?
Yes, yes, and yes. That is, unless the sub panel itself is powered externally from outside the house. There are special rules regarding sub panels, mainly because of the increased current (so, you need larger wire, etc.). But then you have to only run a single set of wires to the sub panel.
In my case, I have all the drywall off the walls of my family room and the breaker box is in the family room. Therefore, I can wire everything to the breaker box and not have to install a sub panel.
I do note that while electricity is dangerous, you also have to understand that the amount of time you spend near the dangerous stuff can be quite low. For example, I installed 16 lights and a "Grafik Eye" (a controller with four zones and 16 scenes; each zone can handle a certain number of lights and each scene can control each zone). It took several weekends to put up all the recessed lights, drill all the holes, route all the wires, and connect everything. The only time high voltage was involved was for about 10 minutes, when I dropped the power to the house and installed a 20 amp breaker and connected a set of wires to this breaker. Other than that, the entire rest of the time was spent without any danger from voltage.
