I've been building a large extension on my home that's turning into a life long project .My sparkies installed a couple of main lug sub panels throughout the extension and existing home .They installed the breakers a couple of weeks ago and fired up the panels and checked to make sure everything was in working order . So everything looks good and I'm finally excited to begin rocking . My sparkies show up Saturday morning and start pulling out a few breakers from the panels and replace them with arc fault breakers that cost $30 ea. If I remember correctly they said I need about 35 of these breakers .I walked away without asking them why. My question is shouldn't they have known about this from the beginning and installed them from day one .I'm also assuming that they are required by code , but when did they become code and why ?