This isn't a problem with the Navien- it's a problem with the installers!
2-1/2 minutes to call hot water to your sink is distinctly NOT normal- it's an indication that it isn't operating correctly. If it's "normal" in the installers' experience, it means they have no business installing a tankless!
A noise that shakes the whole house on startup is also distinctly not normal, and potentially an indication of a hazardous condition. (Improperly purged flue and a flue explosiong on igntion would be my first guess, but not having heard it I won't make that call outright. If I'm right it's a fire hazard now and may turn into a carbon monoxide hazard later if it cracks the plastic flue.)
Tankless units are running just fine with well water all over the world. Water hardness can be a longer term maintenance issue (annual de-liming/descaling), but other than that, the fact that it's on a well isn't an issue.
If it's taking 2-1/2 minutes to get water to the sink, your diswasher is never getting hot water- EVER. If yours is a particularly low-water use dishwasher it may short-cycle the tankless resulting in lower efficiency draws, but unless it fills in 10 second bursts the tankless should be able to serve it.
Thank you thank you thank you
And it really IS 2 1/2 minutes to get hot water. I timed it.
The plumber acted like I was crazy and everyone knew 2 1/2 minutes was normal and that I was hearing things as well. How long SHOULD it take to get hot water to a fixture?
He was supposed to come to check things out today, but didn't show up or call. My husband called him at 7 pm and he was short with him because he was at his accountant's office.
The noise is a rumbling, vibrating noise that vibrates the whole house, not an explosion noise. Should I still be worried about fire and CO2 hazards?
So I wasn't dreaming that my dishwasher wasn't cleaning?? what do you know. So speeding up the 2 1/2 minute heat time will fix that?
How about my HE frontloader washer? Is it getting hot water if the water takes 2 1/2 minutes to heat?
Thanks again