Recommendation for a tankless water heater

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Baltik

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I need to relocate my existing 80gal tank unit. Given it's 11+ years old it seems like a replacement is in order as well. As it stands, hot water takes a long time to reach the kitchen so clearly a recirc is needed. Gas line access is easy so that's not an issue. Hoping for a 9+gpm unit for a family of 4, Navien 240 series seems to be popular here, any other units to consider?
 

Jadnashua

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What is your wintertime input cold water supply temperature? People look at the top line gpm ratings, but often fail to notice what they're using for inlet temperatures...the further north you go in the USA, the colder the supply water can get, and that can make a huge difference in the hot water output of a tankless. Think of it...9gpm is 8.34*9 then *60 for an hour, and that's over 4500# of water you're trying to heat up. 199000/4500=44 degrees max temperature rise...that would mean, to get 120-degree water, what's considered normal for a home at full hot, your incoming water would have to be 120-44, or 76-degrees...and, that's assuming the thing was perfect in the heat transfer (it's not). That 199.000 value is about the largest tankless burner. YOu can gang multiple ones together, but your inlet gas service will need to be huge.

I haven't kept up with the details, but didn't SF just implement some new regulations regarding NG appliances? Check those out carefully. Not sure when they start, or exactly what applies or how, but you may not be able to do this.
 

FDNY/RETIRED

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I could tell you I live in NY, Long Island right off the water. I have a Navien NCB-240E. My Domestic hot water heater side is 199,00BTU's. I live in a Split Level Ranch and I can run a shower at my top floor. Which is 80 ft away from my boiler with just the recirculation pump in the unit. With my unit set at 120*F, in the winter with below zero temps outside. It takes less then a minute to get hot water upstairs. I can run a dishwasher 25 ft away from the tank. Or my Washing Machine maybe 6 ft away from the tank at the same time. I have run both showers the one on the 3rd floor and 4th floor. Have someone turn on the kitchen sink or flush a toilet. No drop in pressure but maybe 3 seconds of the water in a shower getting a smidgen colder.

Now since mine is also my heating unit and though the 3 way valve cuts the heat off. I had no problem in my Domestic hot water supply at all. When the weather is in the 40's and now going into the 70"s. I find I have to turn the hot water mixing valve on my showers. Almost half has much less, then when it was in the low 30's to subzero temps. I am running the orange restrictor. Which gives me a 5.6GPM flow.
 
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