What to replace my Noritz NRC111-DVNG with? It has a very noisy vent fan.

[slinmv]

I had a NRC111-DVNG installed back in 2020 in an open walled closet (no wallboard on the inside, stucco on the outside) in the garage. It was quiet during operation, but the vent fan would run as soon as the hot water stopped flowing to clear the chamber of gases and it was super loud. We could hear it clearly in the kitchen about 25 feet away, and even further away in the house. I spent time lining the inside of the closet with MLV (mass-loaded vinyl) to reduce the noise to an acceptable level. The installation guy said it was normal, but I find that hard to believe. But, I also don't see many people online complaining about fan noises from their tankless water heaters, even this specific unit. So, was it somehow a poor installation/configuration, or just a loud unit?

We're remodeling the house now, and I'm pretty much planning to throw that unit away and replace it with a quieter one, but I have no way of knowing which units not only run quiet but do not have any loud fan noises after the unit is done running. My neighbor has a Rinnai RU98e installed back in 2014 which he let me listen to operating and it seems super quiet. I can't even hear a fan come on after it's done running.

I'm thinking about getting the RSC199eN and plan to mount it to the external wall of the kitchen. Does anyone have this unit and can confirm that it is quiet all throughout its operation? If it makes anything resembling the same noise I heard from the Noritz I'll be super pissed especially as the kitchen will be a lot closer to it now.

Thanks!

 

[GReynolds929]

Prepare to be super pissed. All tankless water heaters I've installed make almost identical noises. Like your plumber said, what you've described sounds like normal operation to me. You could call manufacturers and see if they can tell you the decibels the fans create when running.

 

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[Lifespeed]

Sound is conducted as well, depending on the structure it is mounted to it can act like a drum, resonating with normal water heater sounds. Bolted to studs with stucco on the outside is likely worsening the issue. There is a lot on the internet about soundproofing walls, search "green glue" to start. Not to say this alone is the solution, but applying de-coupling techniques to the water heater mounting is likely your best shot at a quiet(er) heater. There are elastomer isolation mounts available, check for load orientation and weight ratings. Most don't find these necessary, but you expressed concern.

My Navien NPE 240S is screwed to 3/4" plywood which is in turn screwed to the studs in the attic above the bathroom. I can hear it it faintly, but there is 10" of blown-in fiberglass on the ceiling below it.