With the increase of additional circuit's in some residentual renovations and customers can't afford service upgrade to 200amp. I trying to find a solution for where to put these new circuit's many are 3wire cable runs needing a 2pole circuit breaker and running out of room. I know one solutio is to install a subpanel but I was wonder about a 40 space 100amp main panel. . Does it exist if not why not?