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Thread: How quiet is a Rinnai tankless, *really*?

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    DIY Member dimprov's Avatar
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    Default How quiet is a Rinnai tankless, *really*?

    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!

    David
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    Last edited by dimprov; 02-22-2009 at 06:59 PM.

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    DIY Member dimprov's Avatar
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    For instance, Eternal gives the "maximum noise" for it's different models, although it's ambiguous as to whether Eternal's db refers to db(a) or some other reference.

    Ideally, I'd like to see the SPL's at different frequencies so I could pick the most appropriate soundproofing materials, but I'm not too hopeful of finding that information, unless someone here has done their own measurements at a 1 meter distance that they're willing to post.

    David
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    DIY Senior Member BimmerRacer's Avatar
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    I have an R85i in my basement. Send me a decibel meter and I'll measure it for you . I will, however, say that it's pretty quiet. HTH

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    DIY Member dimprov's Avatar
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    BimmerRacer,

    Does its loudness vary depending upon demand (i.e. maximal versus minimal water heating, such as all taps open versus a single faucet)?

    David

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    DIY Senior Member BimmerRacer's Avatar
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    Just did the test with three sinks going. Yes, it does get louder. How loud? Well, standing right next to it with all three going, it was overpowered by the sound of water hitting the base of plastic utility sink about 10' away. It is also MUCH more quiet than my new Bryant Evolution heat pump and I think that one is rated at 85dB or somewhere near there. Also, do realize that there are different ways to measure sound and it's likely that Bosch, Rinnai, Bryant and everyone else in the world do not follow the same standard. It is sort of like comparing treadwear ratings between Michelin and Bridgestone and purchasing a Michelin because it has a higher treadwear rating and therefore should last longer. Not quite that simple as it turns out

    YMMV

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    DIY Member dimprov's Avatar
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    Thanks for running the test, YMMV. It proves that loudness varies with demand, and therefore a single number of 49 db(a) can't be right.

    I think I'll assume 49 db(a) is the low end. If the newer Rinnai units manifold the way the older Rinnai units did, then by running 3 Rinnai tankless units in a manifold I can push the aggregate noise toward the lower end of the scale than if I were to use fewer, higher capacity, units.

    David

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