These heaters are used more and more for hydronic heating...So I don't know how a regulatory body can see it any different than what it is? I don't know how they distinguish between Boiler and Heater! For me where I live, there are no inspections, but its common knowledge (and probably written somewhere in a code) that anything over 200K BTU requires a certified technician to do the install...Anything under 200K can be installed by the owner....Hence 199K BTU...My floor'heater works great and has for over 10 years now. And it only runs at 105° output temp of the heater. So not even close to being in the "Boiler" range! At 32°, the heater cycles 15 minutes on, 15 minutes off to keep the bays ice free. About zero, it cycles on about 20 minutes, off 10 minutes...It doesn't matter how cold, the cycles are always 30 minutes...Thats with a 15° differential.
So yea, why would you spend all that money for a "Boiler" when a "water heater" does the same thing just as good only cheaper!?