How much noise does a Navien tankless waterheater NR-240A make?
How much noise does a Navien NR240A make?
When not in use, the NR240A is virtually silent. However, when hot water is being generated, a fair bit of noise is generated. How much seems to depend on how hard the heater has to work. For larger volumes or hotter water, there is a fair bit of noise. It is not unlike the sound a diesel truck idling outside at the curb makes . Most of the noise seems to come from the fan running - and presumably it runs at a faster rate as the water heater works harder.
In many homes the unit will be in the basement with a tendency to hang it on a concrete wall. You can help reduce vibration and noise by screwing a piece of plywood or the like into the concrete, and then attaching the Navien NR240A to this wood. Insulating the intake and exhaust pipes may help to reduce noise too (as well as improve thermal efficiency).