Navien NPE-210A2 vs NPE240A2

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bathreno

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The plumber installed the wrong Navien tankless water heater. I asked for the NPE240A2, and he installed the NPE210A2. He says he can exchange but thinks the 210 is sufficient for our needs. We have a 3-level home: tankless heater in garage with the W/D and a powder room, kitchen and powder room on level above, and two full baths on top floor. We've taken a few showers - felt fine. We weren't running anything requiring hot water at the same time - just one shower at a time. I researched at length and decided the extra few hundred was worth it to have the 240, which also had better reviews. Any plumbing/water heater specialists here who can weigh in? Any reason to keep the 210?


Plumber also noted that our kitchen is a little far from the heater and suggested we install a recirculating line to the water heater. However, I thought this Navien product had a built-in recirculator, making this unnecessary.
 

Bannerman

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Both models are equipped identically, but the NPE-210A2 has a gas input capacity of 12,000 - 180,000 BTU whereas the NPE-240A2 gas input is 13,300 - 199,900 BTU. This translates to the 240A2 supporting slightly higher gallons per minute compared to the 210A2 while supplying consistant water temperature. (Compare the Temperature Rise and DHW Capacity ratings at the links below)

Each of those A2 WH models are equipped with an internal recirculation pump and buffer tank. Without a recirculation return line running back from the fixture that is the greatest distance from the WH, the internal pump will not recirculate hot water throughout the home but will only recirculate hot water within the WH which will only maintain the water temperature within the internal buffer tank.

An alternative to a dedicated return line will be to install a NaviCirc valve below your kitchen sink. The NaviCirc will then allow the home's cold water piping to function as the hot water recirculation return line. Since a dedicated return line is always best, the NaviCirc valve will be better suited when hot water recirculation is desired, but where installing an additional dedicated return line would be either virtually impossible or extremely costly.

NPE-210A2 Specification data

NPE-240A2 Specification data

NaviCirc Operation Manual
 
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bathreno

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Thank you, Bannerman. Yes, I read a lot of the literature before I settled on the 240. I wanted to make sure that we had plenty of hot water. What is your sense re the plumber's claim that the 210 is sufficient for our house? We're in San Francisco - so mild weather with the water heater in the garage.
 

Breplum

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The difference in performance is maximum GPM. We have in our climate zone, ground water temp of 65 F. The 210 model will give you full hot flow of 5.4 GPM. The 240 model will give 6 GPM, so, depending on the flow rate of your showers you can calculate say 2.5 GPM showers simultaneous and you are at the limit of the smaller model's range. Whereas, you have a bit more headroom with the 240 but not much. If you have or buy lower flow from shower heads...then a different range for simultaneous fixture use.
Without a dedicated recirc line, you get no instant hot at a fixture as water still has to travel to the fixture even if it is ready to go at the WH itself.
 

bathreno

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Thank you, Breplum. We're in California - so 1.75 GPM. Sometimes we have two showers, the dishwasher, and laundry going at the same time - so I guess every gallon counts.
If I'm OK with waiting a minute for hot water in the kitchen - can I do without a recirc line? That is, am I stressing the WH in any way by not having a recirc line?
 

Bannerman

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When considering the flow rate to a shower, what will ge disharged from the shower head will usually contain some percentage of cold water mixed in since 120°F water directly from the WH will be too hot for most. In this regard, perhaps 1.4 or 1.5 GPM will be supplied by the WH.

so I guess every gallon counts.
If I'm OK with waiting a minute for hot water in the kitchen -
Hot water recirculation will usually reduce water wasteage in being forced to allow water to flow to drain waiting for hot water to arrive.
 

bathreno

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Thanks, Bannerman. The concern is with the kitchen. I don't need the hot water to come instantly, and I'm using the cold water rinsing/washing - so not much wasteage.

So no stress on the system if there's no recirc line?
 
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