Tankless question
#11
I'm looking at swapping over to a Navien NPE-240A tankless.  My water heater is going on 10 years old and if I'm going to do tankless I would like to do the change when it's convenient, not when the tank goes bad.

I spoke with my wife's cousin, who would by the person selling me the Navien.  The one thing he brought up that I had not considered is the GPM and the fill time for the bathtub.

The Navien is rated at 5.6 gpm, he said in real world applications customers are seeing closer to 5 or just under.  He said it can almost double the fill time of a bathtub depending on the flow rate or my tank water heater.

What my question is, for those of you that have made the switch, and you have family members that use a tub, what has your experience been as far as tub filling?  Have you enjoyed the switch?  Regret the switch?   We don't have a whirlpool tub, it's a 60" tub but it is a deeper soaking Kohler tub.  My wife and kids don't do a lot of baths but, maybe once every couple of weeks.  We are mainly a shower family.

I'm sure many of you will bring up the gas meter size, piping size...I have a 400btu meter.  I put in a pool heater a few years ago and when I upsized the meter they put in a much larger one than what I needed.  With that size, I can run the pool heater and the water heater at the same time.  I wouldn't have much more headroom above that, so I'll see how we do.  I'll probably do a monometer reading once I get going and see where I stand.  I can always upsize again if needed and manage my gas load until that would happen.  I have sized the gas line diameter appropriately.

I am considering the switch for the "limitless" hot water not the energy savings.  I have two daughters and a wife, right now with my 50 gallon tank we can get two showers then we have to wait a half hour to regen the 50 gal tank and usually the second person showering is getting luke warm water by the end of the shower. 

Thanks for the input!!
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#12
Can't answer but I have been looking at one for our new build and decided against it. Just the two of  us, no kids. For use there is minimal energy savings.  Plus if the power goes out you have no hot water and that was the thing that changed our mind.

We are going to live on a long dead end road with few houses, lots of woods and I suspect power outages will happen and we will be last on the list if there is a storm damage. Tornado a few years back left us without power for a week. Gas tank heater and still  had how water.

One thing I wanted to point out was keep in mind  you need to descale the heater once a  year.... depending on how hard your water is, you might have to do it twice a year. Not a big deal but something I did not know till recently.
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#13
Made the switch a couple of years ago. Two daughters and a wife like you. LOML wanted as much scalding hot water as she wanted.

I did a measurement and could fill a 5 gallon bucket in 30 seconds from an outside faucet with the faucet wide open. So I figured I could flow 10 GPM max. I then picked a unit that could flow 9.5 gallons per minute (pretty close). I recall the base model only flowed like 6-7 GPM.

LOML now has all the scalding hot water she can stand. Even said after the switch that it was a little too hot. ?????

I did my own install and have a very keen idea of the costs. Note that the heater itself was about half the total cost of my unit (Rinnai). By the time I added in the recirculation valve kit, a cover for said kit, the concentric intake & exhaust piping, and a few supplies for the gas line, the bill had doubled.
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#14
(02-11-2021, 12:51 PM)DieselDennis Wrote: Made the switch a couple of years ago.  Two daughters and a wife like you.  LOML wanted as much scalding hot water as she wanted.  

I did a measurement and could fill a 5 gallon bucket in 30 seconds from an outside faucet with the faucet wide open.  So I figured I could flow 10 GPM max.  I then picked a unit that could flow 9.5 gallons per minute (pretty close).  I recall the base model only flowed like 6-7 GPM.  

LOML now has all the scalding hot water she can stand.  Even said after the switch that it was a little too hot. ?????

I did my own install and have a very keen idea of the costs.  Note that the heater itself was about half the total cost of my unit (Rinnai).  By the time I added in the recirculation valve kit, a cover for said kit, the concentric intake & exhaust piping, and a few supplies for the gas line, the bill had doubled.

That is a really high flow rate.  The model I am looking at is their highest end consumer model they sell, and is the highest consumer BTU unit.  200K BTU and it is nearly 99% efficient.  I probably should have specified that I need a 70F temperature rise will be 5 GPM flow rate.  It will flow higher amount but not at that temperature rise.  

Thanks for the input
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#15
(02-11-2021, 02:47 PM)Andydiy Wrote: That is a really high flow rate.  The model I am looking at is their highest end consumer model they sell, and is the highest consumer BTU unit.  200K BTU and it is nearly 99% efficient.  I probably should have specified that I need a 70F temperature rise will be 5 GPM flow rate.  It will flow higher amount but not at that temperature rise.  

Thanks for the input

I think you are looking at the same size as the 9.5 GPM units.  Mine is a Richmond 195K BTU, manufactured by Rheem.  It is rated at 9.5 GPM at 50F rise.  There are a lot of factors to look at.  I use well water and the water enters my house at 52F.  Do you know the entering water temp?  That will tell you the flow rate to fill a tub.  Now, most people set the temperature wrong on the tankless unit.  You shower or bath at a temperature below 110F so why set it at 130F like the old fashion tank units.  Supplying 130F to the bathroom to just dilute it with cold water is not wise.  When you have a tank of hot water, you set the temperature high to insure you have enough hot water.  

Next, the less water you use in a day, the better a tankless works. I live alone so I use hot water for the shower in the evenings.  When I changed from the tank to a tankless, I reduced my annual propane usage by 1/3.  My propane is only used for hot water and a cook top that is seldom used.  So for those who say it does not take a lot to keep that 50 gallons of water at 130F 24/7, sorry, you are wrong.  I heard that force air blower kick on often throughout the day to keep the water hot.  I even had a thermal blanket around the water heater.
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#16
(02-11-2021, 09:14 PM)aquaticjim Wrote: I think you are looking at the same size as the 9.5 GPM units.  Mine is a Richmond 195K BTU, manufactured by Rheem.  It is rated at 9.5 GPM at 50F rise.  There are a lot of factors to look at.  I use well water and the water enters my house at 52F.  Do you know the entering water temp?  That will tell you the flow rate to fill a tub.  Now, most people set the temperature wrong on the tankless unit.  You shower or bath at a temperature below 110F so why set it at 130F like the old fashion tank units.  Supplying 130F to the bathroom to just dilute it with cold water is not wise.  When you have a tank of hot water, you set the temperature high to insure you have enough hot water.  

Next, the less water you use in a day, the better a tankless works. I live alone so I use hot water for the shower in the evenings.  When I changed from the tank to a tankless, I reduced my annual propane usage by 1/3.  My propane is only used for hot water and a cook top that is seldom used.  So for those who say it does not take a lot to keep that 50 gallons of water at 130F 24/7, sorry, you are wrong.  I heard that force air blower kick on often throughout the day to keep the water hot.  I even had a thermal blanket around the water heater.

Yep, I call turning up the temperature on a tank water heater, "cheating for a bigger tank."  I already have it set pretty high to have an effectively larger tank.

 Navien says 5.6 gpm at my ground water temp (45-55F) and 70F rise, but I am being told a more true to life figure is closer to 5 gpm.
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#17
You do not want to make a mistake with this. IMO you REALLY need to get a rep out there to look at everything and be sure you get the right capacity. Around here most gas companies sell them.

We changed our mind when a Rinnai installation came up to >$2000 with running the gas line + plumber.

For us, it would be cheaper to install a second hot water heater closer to the distant source. We would have stuck it in a closet.
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#18
We have a Rinnai, gas fired, was already installed when we purchased the house.
Very happy with it. Not having to pay to store hot water and a lot more room where all the house mechanicals are.
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#19
Two showers and you are out of hot water with a 50 gal tank?  How long are those showers?  I had no issues with a 30 gal NG hot water tank for 25 years with my wife and I.  When it came time to replace I upsized to a 40 gal one only because it was more efficient.  The math just never makes sense for tankless hot water heaters.  I'd get an 80 gal conventional unit before going to tankless. My gas bills are less than $30/month in the Summer when the only thing consuming natural gas are my hot water heater and grill.  

I don't know about the units you are considering, but many tankless units need a minimum flow rate to fire.  When you want a low flow of hot water you get nothing but cold water from some of them.  That's as annoying as running out of hot water.   

John
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#20
I have the older version of this model (CR-240A) and would never go back to a tank model. It was installed in 2009 and has been quite reliable, once it needed a new sensor and I have to descale it once a year. I have only descaled it twice ever though and it's been fine with our water treatment system.

It has a built-in recirc. pump and a timer set for when you want it to run or sit idle. As others noted, it does need some minimum flow to keep it hot but really hasn't been an issue. I have two daughters and my wife and it never quits making hot water for them. 

To your point, if filling a tub during recirc hours there has not been any noticeable time difference in filling a tub. It may be half a minute or more, but not enough to make me think differently. My bigger issue is water pressure and piping size & layout when multiple fixtures are running, but that is due to existing conditions and not the heater.  

A couple things that might help:

- Make sure you glue the concentric cone outside. (I didn't like an person)
- You will need a pipe from the farthest point possible as a recirc line.
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