"User Example" wrote in message
...
I am adding an A/C to my garage and need to add a 240V circuit. The
loadcenter is conveniently in my garage and has plenty of open spaces.
However, I want to make sure I am not overloading it.

What are the rules for adding circuit breakers? The label on the
loadcenter says 120Amp max. but it already has 12 20Amp circuit breakers
in it. 12X20 = 240Amps which is twice the rating. So, I am a bit
confused.

The max rating of the panel is nonsense unless the panel was fed with 125
amp wire. Check the wire feeding the panel and the breaker protecting the
wire...

Do a load calculation on the feeder to the panel including the new load. Ya
also may want to do a voltage drop calculation for the panel with the new
load connected.


http://www.electrician.com/vd_calculator.html