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Old 11-02-16, 02:53 PM   #1
oil pan 4
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Default Water heater replacement, conventional tank to tankless

Well it happened again. The 2nd hot water heater started leaking.
I am going to replace the narrow trailer style gas hot water heater with a tankless gas water heater.
It is110,000BTU per hour 85% efficient unit. I figure it can raise the temperature of 3gpm of water about 62F. Even with cold winter water it should still be able to heat the water up to 100F at 3gpm. It cost $600 and has 4 inch intake and exhaust.
There were more expensive ones, $900 buys a 7.5gpm but the intake exhaust are 5 inch.
I have a 4 inch exhaust for the existing water heater and a 4 inch exhaust for a in wall heater that has been removed.
And I ran a wireceptacle for a tankless heater a few years ago while under the house rewiring some stuff.
So the intake and exhaust holes and electrical are already there. Just add water heater.

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Old 11-02-16, 03:01 PM   #2
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I installed this one Takagi T-H3-DV with 0.95 energy factor
http://ecorenovator.org/forum/renova...er-heater.html
You can use 3” or 4” PVC venting.
http://www.takagi.com/products/tankl...ters/t-h3-dv-n

This works great supper efficient. They make smaller models also. Here two people can shower and run water in the bathroom at the same time.

I have had a few tankless heater. I have been using them since I was a kid. This one is the best by far that I have used.
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Old 11-03-16, 12:18 PM   #3
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That's a pretty good one.
Seems a little big for me.
Just wondering how much does that one typically cost?
I only need enough to run a shower and maybe the dish washer.
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Old 11-03-16, 12:29 PM   #4
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This one might be better for you
T-H3J-DV-N - Takagi T-H3J-DV-N - T-H3J-DV-N Indoor Tankless High Efficiency Condensing Water Heater (NG)

T-H3J-DV-N - 160,000 BTU Natural Gas Indoor Condensing Ultra-Low NOx

This is the same as mine but 160,000 BTU

https://www.acwholesalers.com/Takagi...H0zBoCj2nw_wcB

If you have to buy vent pipe that is expensive. Make sure you add that to the total cost. PVC is very cheap to vent with.
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Old 11-03-16, 08:45 PM   #5
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I've been using a Bosch tankless (battery operated ignition) for almost 20 years.

Mine is a lower efficiency style, but except for an early ignition coil failure, it's been efficient hot water all the way.

I agree with above comments about the size being way too big. I believe the original thinking was to design a tankless that could be 'dropped-in' and replace a full four person family's DHW demands.

But you are not four people, and you are not likely to wash clothes, while you shower, while the dishwasher is running, while someone washes their hands.

I have looked at some of the Chinese units on ebay, and I think that for a guy living alone, one of those units would do it better than the whole house units.

Another consideration is that they do NOT supply instant hot water, there is a heating up curve. Not impossible, but it is there.

It is to your benefit to locate your tankless water heater as close as possible to the most frequently used water outlet. This is not the same as the highest volume outlet.

Good luck,

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Old 11-03-16, 09:01 PM   #6
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I have one of the Chinese units I bought off ebay. It has battery operated ignition. It is a vent free model.

I bought it for the greenhouse. Most of these will not provide hot water more than 15-20 min at a time then they need a rest and they shut down.

Others have built closed loop heaters and they put them on a timer to rest them then run them again.
If you have any question on it or need pictures I have not installed it yet.
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Old 11-05-16, 09:09 PM   #7
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Quote:
Originally Posted by momrebeca View Post
Please, Can you provide where I can one? I`m planning to use it in my greenhouse.
Search ebay, use "tankless water heater", or "demand water heater", or "vent free water heater"

You'll have lots of choices.

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Old 01-09-17, 09:29 AM   #8
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Another thing I don't like about the tank less is it seems unless you buy a big one they restrict flow.
My tankless heater is rated for 4.3gpm, I'm not getting anywhere near that much flow as compared to the old gas heater. The utility water pressure where I am is usually about 100psi.
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Old 01-09-17, 11:30 AM   #9
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This is our tank GPM
Maximum flow rate of 10.0 GPM at 35F temperature rise (5.4 GPM at 70F rise)
You need to know how cold your water it coming to the tank. As you can see it can make a huge difference if your incoming water is very cold and will reduce the flow.

Takagi web site uses pictures to show the flow.

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Old 01-09-17, 05:13 PM   #10
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It heats the water up just fine. I figure a 62F increase even at 3gpm.
It will just not flow any more than about 3gpm.

I assumed a 35F inlet temperature and told the wife that on really cold days she may have to slow down the flow to allow it to warm up more.

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