It looks like an A.O. Smith branded Rinnai commercial hot water heater, not an A.O. Smith design.
ASME rated tankless heaters are usually suitable for space heating & combi-heater as well as commercial hot water service, but usually have much lower turn-down ratios, but according to the spec it's min-fire goes down to 19,000BTU/hr which isn't terrible. (Many residential tankless units can run down to about half that though.) It's max-fire of 237,000BTU/hr is higher than the 199K residential tankless limit, but not so much so as to create a problem in a residential app.
This is also not a condensing unit- the raw combustion efficiency on it is about 85%, which would require stainless steel Z-vent rather than PVC for the exhaust, which adds quite a bit to the installation cost. Sometimes it's cheaper to go with a condensing heater and PVC venting when the venting runs have any substantial length, avoiding the high material cost of the stainless.