I am renovating a 1920s home and it was rewired in the late 70s-80s. The is an old 3-phase box that is no longer in use, then there is second a large breaker box that has 40 breaker slots in it (actually it shows on the list 1-40 but many of the breakers have been assigned two numbers so there are more like 20 actual breakers--that brings up a whole other question for later). One place on the box says its a 150 amp max and another place it says its a 200 amp max. The way I understand it, the breaker total should add up to this max (considering 80% usage). Is this right? What I don't get is how is this total supposed to work if the box holds this many breakers even at 15 amps apiece that doesn't add up right. Why would a box hold more than its max at the minimum of 15 amps. My box has a few 15s but mostly 20 and 30 amp breakers. In addition it has two wires connected to about 3 of the breakers (double lugged??). I am going to take some photos of the box and/or draw a diagram today and I'll try to post them. I know that several of these breakers were assigned to 220 AC units which I no longer need and would like to reassign, but in the process, I want to make sure it's all in compliance and safe. Many more questions to come--this house is a case study for everything under the sun--my boyfriend calls it the money pit.