Hot Water heater (natural gas) selection- Rinnai tankless? - Page 3 - Smart Car Forums
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post #21 of 28 (permalink) Old 11-17-2017, 11:28 AM
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Glad to help. I don't know much about tankless water heaters I'm afraid. Only have messed with conventional ones
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post #22 of 28 (permalink) Old 11-17-2017, 01:45 PM
 
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Originally Posted by jzchen View Post
Haha haha.

What’s concerning about the tankless type is something called a “cold sandwich”! (Hungry, anyone)? Still trying to sort that concern out....
I've used the gas fired tankless water heaters a lot in Germany where they are quite common.

If you drop the flow of hot water below the minimum at which the burner will fire, the burner shuts off leaving you with cold water.

So consider the following two scenarios...

You take a navy type shower where you shut off the water while lathering up... the dribble shower head does not draw enough water so the burner shuts off... the small flow of water through the water heater is now cold, and fills the hot-water line... turn the shower head back on and you get a load of cold water until the hot again reaches the shower head. You just had a cold sandwich!

I like to use a small flow of water at the kitchen sink when peeling potatoes... in the winter the incoming cold water is so cold that it hurts my hands... so I mix in a bit of hot water to warm it up. I found I couldn't do this in Germany as it did not produce enough flow of water to keep the burner on and increasing the flow rate was such a waste of water.

Using a tankless water heater requires some relearning of things. For example, set the hot water flow rate at the shower and make your temperature adjustments with just the cold tap. If you reduce the hot water flow, its temperature will typically increase a bit... which is counter productive to adjusting temperature. If you have a single lever shower control... well... you're on your own!

~toaster
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jzchen (11-18-2017)
post #23 of 28 (permalink) Old 11-18-2017, 03:01 AM Thread Starter
 
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Hot Water heater (natural gas) selection- Rinnai tankless?

Thanks toaster. Very good info. I had read about the cold sandwich, and am still perplexed at the phenomenon. I guess they can’t leave the burner on an “off” time delay because this may boil the little water where the burner cooks it. Some of them I read will decrease flow rate until the water reaches the set temperature. I wonder how that affects the challenge of adjusting the temperature in a shower....

We live with my parents in their house. Strangely this broken 50 gallon tank water heater seems to feed only two bathrooms, and that’s it. The other 50 gallon feeds the rest of the house, (house is 4000 sq ft), and is still working just fine. I guess the low use may have something to do with the failure compared to the other, much more used one....

Oh well. Still prefer the electric one because EcoSmart provides a lifetime warranty. (Me and my love of lifetime warranties). But I was warned it is more expensive to run electric, and it is most likely true because before we got solar I calculated $0.28/kWhr for a years use. (We are on a tiered rate).....

I have to watch the specs carefully as some of the tankless natural gas water heaters use 3/4” gas line fittings, but I believe the pipe to the current one is only 1/2”....

Then there is cost. The more efficient you want the more they cost! (Condensing ones which are the highest efficiency, cost the most). Then there are venting concerns.... Amazon seems to have good pricing so far, (where you can purchase “expert installation”as well).

Wonder how much eBates cash back that may earn me, (for home services).....
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post #24 of 28 (permalink) Old 11-18-2017, 09:41 AM Thread Starter
 
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Glad to help. I don't know much about tankless water heaters I'm afraid. Only have messed with conventional ones
The original one is so big, I will not be able to move it on my own. That's part of the reason I am intrigued by these tankless units. Much more manageable if something goes wrong. Then when I was in Home Depot to get something, I went by the water heaters and there are some tank water heaters are quite expensive as well. Labor around here is even MORE expensive than the heaters.......

Thanks again. I think I'll go watch some more.
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post #25 of 28 (permalink) Old 11-18-2017, 03:13 PM
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You have to drain the water and rust out f them before you move them, makes them lighter.
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post #26 of 28 (permalink) Old 11-20-2017, 11:31 PM
 
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I've had a Navien Premium Condensing Tankless Gas Water Heater (NPE-A) since about 2007 and love it. No muss; no fuss; and no issues other than having to flush it out once a year which is a Saturday morning job. Highly recommend it.

NPE-A series | Navien

George
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TX
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post #27 of 28 (permalink) Old 11-22-2017, 05:46 AM Thread Starter
 
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I've had a Navien Premium Condensing Tankless Gas Water Heater (NPE-A) since about 2007 and love it. No muss; no fuss; and no issues other than having to flush it out once a year which is a Saturday morning job. Highly recommend it.



NPE-A series | Navien



George

2015 BRABUS Coupe

TX


Thank you George!

I’m afraid the link is not working on my iPad, but going to us.navien.com has a lot of nice info. Seems like they have a longer warranty than others just off the top of my head in the middle of the night. (I think I may have to take our dog to the vet when they open. Something’s wrong...)


Thank you again for another option. It is always nice to have options. (And I didn’t see a Prop 65 warning while I was on their site to boot!)

Sincerely,
Jesse
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post #28 of 28 (permalink) Old 11-26-2017, 11:28 AM Thread Starter
 
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Ended up taking our dog to the ER vet while the rest of the family went to Thanksgiving dinner! About $700 later my wallet was feeling light. So Black Friday I saw a cheap water heater option available on Amazon and pulled the trigger on it for now. If it doesn't work out at least my investment is minimal.

Eccotemp FVI12-NG

(I get to test Amazon's customer service if there is a problem with it...)
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