If this help here's what I know. I've been wanting the earth mountain man 500 for a couple years and it wasn't EPA phase 2 compliant so I had a few issues with my zoning officials. I've done research and the info I've found on Shaver's web site helped me get the earth mountain man 500. If you purchase a furnace with grates and a ash pan it can be used for coal and there are no EPA emissions on a coal burner in Pennsylvania and if the burner is over 300,000 btu's that also makes it exempt of state laws also. So thanks to Shaver and their website and the research I've done I got the OWF I've been wanting and it works great!!! I've also learned a lot off this site and the outdoorwoodboiler.com site also. A lot of people here are on that site also. It's a grate community and they make you feel like family. I hope this helps you out and if you have more questions I'm sure someone will be gladly to help out, that's why I check these sites out daily, there's always good info and great knowledge.