So I also went looking in the NEC for the 10% rule and didn't find it either. I did find this however: 408.54 Maximum Number of Overcurrent Devices. A panelboard shall be provided with physical means to prevent the installation of more overcurrent devices that that for which the panelboard was designed, rated, and listed. For the purposes of this section, a 2-pole circuit breaker or fusible switch shall be considered two overcurrent devices; a 3-pole circuit breaker or fusible switch shall be considered three overcurrent devices. Sooo... while it has 37 circuits, this panel also has 46 overcurrent devices in it. I guess if Square-D lists a maximum number of breakers as part of the rating then you would need to compare that to see if the panel needs to be written up. I bet there isn't such a spec though or you would think that the construction of the panel itself would be a violation of 408.54. [:-bigeyes There's a few other nit-picky things that would bug me about this panel though. For example, shouldn't those white wires on the bottom 2-pole breakers be coded hot? To me that's sloppy at the very least and would cause me to become interested in the other end of the branch circuits...