Modine HD Venting

CrawlerHero

Hey guys I need your help, I think I’m missing something on a typical scenario in my area that always passes inspection but the way I read the venting tables, it shouldn’t. Modine hd 30,45 or 60 in a residential application. 4”x3” 26 ga connector on the back of the unit with a short amount (usually 2-3’) of single wall that either ties into a b-vent t or b vent pipe terminating vertically as a cat 1. Looking at the venting tables I can’t see many if any scenarios were the unit heaters meet the minimum BYU’s required for fan assisted venting. Any help or clarification on this would be much appreciated, thank you everyone!