I'm considering the purchase of multiple Rinnai tankless hot water heaters for a remodelling project where maintaining quiet is one of the design objectives. Rinnai claims its tankless units are quiet, and claims a noise level of 49 db(a) across its range of tankless models--see attached. However, when I look at the Bosch noise level data, it claims a range of 45 to 65 db(a). i.e. a 100x difference in possible sound pressure levels, depending on...? I have no direct experience with either brand, but I suspect the Bosch numbers are more "honest" for common sense reasons: it makes sense that the direct-vent blower on the tankless would make less noise when it is consuming its minimum 19,900 BTU's than when it is burning it's maximum 199,000 BTU's. I therefore suspect that Rinnai's 49 db(a) noise rating is marketing spin and reflects the noise level at the lowest end of its range.
FWIW, I did contact the local distributor for Rinnai, and he was useless.
I've come here to get the facts from anyone with actual experience or knowledge of Rinnai units. I can design the soundproofing plan accordingly if I know what I'm dealing with. I can't be shooting in the dark only to find out my assumption is off by 100x because of sleazy advertising!