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Tankless Water Heaters


rlskfoster
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Hey guys we are building a new house and the builder asked me today if we wanted to go with the tankless water heaters. i remember some posts awhile back that kinda suggested they were less effective after five or six years.

This is an 1800 dollar upgrade and I am having trouble deciding if it is worth it. The manufacturers state they are 30 to 50 percent more efficient with twice the average life span of a conventional Water heater and you never are without hot water. We would also get a 300 dollar tax credit.

This is a natural gas unit bu Noritz I think.

Any thought or experience.

Thanks,

Buster

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Tankless design is intended to be built around "point of service" use; build a giant condo tower and have individual water heaters @ each kitchen/bath, or whatever. Frees the building design of central water heating equipment, circulation loops, ets. A single cold water feed to each unit is a nice way to plumb a building. Same thing w/a very old European buildings retrofit w/new bathrooms; no central heating equipment, only one pipe to each unit.

Fast forward to American house design; we have no point of service; all equipment is in the bsmt. (or wherever). If your new MBR bathroom is on the 2nd fl., you have to wait for the hot water; you introduce substantial standby loss. One of the greatest inefficiencies w/water heating is the standby loss; on demand heaters are all about standby loss.

There is no way to install a passive/active circulated loop w/a tankless to eliminate the wait & standby loss. You wait, & you waste energy.

So, IOW, I don't think the benefits of tankless design have been grasped by the average American plumber or building designer; they're still designing stuff the old way and plugging in groovy new technologies that are intended to be used another way, and wasting energy just the same.

Personally, I'd get a 75 gallon (or greater) tank, spend the extra money on a passive/active loop, insulate the heck out of the hot water lines, & that would be my system.

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If you're paying 1800 for tankless as an upgrade it's too much. An 1800.00 dollar pay back may not occur in the unit's life.

The difference in price between a Bosch Aquastar 200K btu demand unit and a 50 gallon conventional WH is about 500 bucks..That can be justified.

If you have a big jacuzzi that holds 80 or 90 gallons and you plan on using it more than the national average of 7 times, then the tankless can be justified as well.

4 or more children is also a motivating factor when considering a tankless.

Net energy savings aren't as great as proclaimed and temp fluctuations at low volumes (shaving) are common.

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Originally posted by rlskfoster

Hey guys we are building a new house and the builder asked me today if we wanted to go with the tankless water heaters. i remember some posts awhile back that kinda suggested they were less effictive after five or six years.

This is an 1800 dollar upgrade and I am having trouble deciding if it is worth it. The manufacturers state they are 30 to 50 percent more efficient with twice the average life span of a conventional Water heater and you never are without hot water. We would also get a 300 dollar tax credit.

This is a natural gas unit bu Noritz I think.

Any thought or experience.

Thanks,

Buster

I mostly agree with what Chad & Kurt said. The $1,800 sounds like waaaay too much. In my experience, a conventional gas water heater can be installed for about $600 and a tankless for about 1400. That's a difference of $800. Where's the other 10 bills going?

Next, is there any hard evidence that these things will last twice as long as a conventional water heater? Most of what I've heard is that they might go for 20 years at the outside. Conventional water heaters in my neighborhood last about 15 years.

A tankless water heater may never run out of hot water, but how often is that an issue for your family? I have a family of 5, including three teenagers. Our 50-gallon propane water heater has never gone cold. (Of course, after the kids have been in the shower for about 10 minutes, I slowly close the water heater's shut-off valve. It's part of my policy of "cold love.")

I have a hard time believing that these things save all that much money via the elimination of standby losses alone.

There's also the human factor. When people *know* that they have access to an unlimited amount of hot water, they use more. Might this offset the energy saving benefits?

- Jim Katen, Oregon

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Originally posted by Jim Katen

Originally posted by rlskfoster

There's also the human factor. When people *know* that they have access to an unlimited amount of hot water, they use more. Might this offset the energy saving benefits?

- Jim Katen, Oregon

Excellent point. One of the reasons I've never updated my 50 gallon tank is the kid takes showers for as long as the hot water holds out.

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Hi,

I think they've come a long way in just the past 5 years, but I don't think I'd want to rely on just one tankless water heater, given where they are now. Give them another 5 to 10 years of development maybe they'll be there. I think that you might consider ensuring that your flue is configured in such a way that replacing the water heater in the future with a tankless will be possible without needing to make major alterations in order to up-size the flue for a tankless.

Check out A.O. Smith's new Vertex line of water heaters. These were co-developed by A.O. Smith and the U.S. DOE and will allegedly provide 70 gallon performance with a 50 gallon tank, meaning that, unless you've got two teenagers showering at the same time, you'll probably have unlimited hot water.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by kurt

There is no way to install a passive/active circulated loop w/a tankless to eliminate the wait & standby loss. You wait, & you waste energy.

Not true. I have a re-circ loop installed on my own home and it works great. . . .HOWEVER, I also supply my entire hydronic in-slab heating system from the same on-demand unit.

There's so many valves, pumps, lights and gizmos on my system that my head spins every time I try and decipher what the whole system is doing. I think my radiant heat guy tricked out a way to get the re-circ loop in there somehow. There may not be a way for Buster to get a re-circ loop on his "plain jane" system.

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Totally different animal.

Supposedly, there's some sort of switching mechanism available that allows one to kick in a circulator when the unit fires, or something like that, so you get water quicker; I think it's the industry's "answer" for the wait & waste thing.

You got any pictures or spec's of your system? I'm contemplating one for my own building project.

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Kurt - I'll get some pictures posted soon. I think its a pretty cool system if I may say so myself.

I'm still trying to figure if the guy that installed it is a genius or this was one of his first projects of this scope. I'm heating around 2300 sq. ft. and have 6 different zones. It took him several return trips to tweak and modify many of the components but has now been working well for 2 + years - no problems.

Don't know if I'm saving energy - I've never heated this much space before with forced air or other systems so I can't compare. The heat quality is definitely much better. No blowing air or dust or drafts. Everything is 'consistent'. And with so many zones, I can just heat whatever area we're using (which is now almost all of them given our recent addition of 4 kids).

This will be our first winter with most all zones running. We'll see if the on-demand unit can handle the load. BTW, I'm also supplying potable water to two bathrooms from the same on-demand unit. I'm having a hard time believing myself that it will handle but we'll see. Again, the guy was either a genius or he was out of his league on this project.

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Sounds like a competent installation. If the design is right, it will do everything fine, I'm sure.

The systems I see all need tweaking for a couple months; getting all the mixing valves balanced & thermostat settings on target takes a while, but once you got it in line, you never have to touch it again.

What's your flooring material? A common balance in Chicago is 1:1, i.e., one linear foot of pipe for one square foot for ceramic stone floor, and 2:1 for carpet or wood.

Do you recall how many linear feet of tubing he installed per square foot of floor area?

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Originally posted by randynavarro

Anybody want to 'confess' how they'd inspect something like this?

Oy! I sure as hell wouldn't pretend to understand it, so I'd look for obvious problems (leaks, corrosion, wiring issues, etc.) and just try to run the stuff and see if it worked. Beyond that, disclaim and recommend review by some who does actually understand it.

Brian G.

"I Don't Know" Are Not Forbidden Words [?]

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Ya know, when you start breaking the thing down into the simple component parts, they really aren't that complicated. They just look that way on the front end.

The really hard part is the stuff we can't see anyway, i.e., how much tubing is in the floor. Everything else is basic hydronic heating, multiplied to several zones & controls.

Personally, I dream of the day I can build a new home w/that system.

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You're right Kurt. The concept is very simple. But the combination of parts, valves, mixers etc. can really get very complicated. The physics for lack of a better term, of water flow is the tricky part.

I'm starting to see more of these radiant heat systems yet I've never seen two that are the same. Its funny how we'll see the typical forced air, natural gas heat duplicated over and over again but not on radiant systems. I've seen components and parts that I've never seen before and haven't seen since. Why are they installed that way?

I've got boiler plate in my report that basically says these things are really more of an art form than an excact science. Like Brian, I'm just looking for leaks, corrosion, and bad wiring. Whether the system performs as intended is way outside the scope of my work!

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Originally posted by kurt

What's your flooring material?

4" concrete slab
A common balance in Chicago is 1:1, i.e., one linear foot of pipe for one square foot for ceramic stone floor, and 2:1 for carpet or wood.

Do you recall how many linear feet of tubing he installed per square foot of floor area?

We didn't calculate that way. I installed the tubing myself under the guidance of the contractor - its the easiest part!! We basically "filled" the flooring using a simple pattern: One run 6" from the exterior perimeter and the adjacent run 12" from that one. After that we ran 18" on center. Just rolled the tubing back and forth across the floor avoiding the interior wall plates.

Maximum tubing run is 300'. The largest zone in the home which is Living Room, office, Kitchen and hallways was 5-300' runs (give or take). Here's a couple pics.

Download Attachment: icon_photo.gif FloorTubing1.JPG

35.15 KB

Download Attachment: icon_photo.gif FloorTubing2.JPG

37.48 KB

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You don't have anything on the concrete, i.e., no finish flooring?

Not that I'm opposed; I really like dyed finished concrete.

And, what's your heat source?

Most of the reason we never see two system's the same is everyone is approaching this like they do everything else in construction; they ignore the mfg's. & make stuff up on their own. At least, that's how it happens in Chicago.

The whole concept of primary & secondary pumping loops is (more or less) ignored by most contractors. Length of run is argued about, spacing of tubing, some of the systems use glycol heat exchangers, some don't, etc., etc.....

It's a lot of parts. What gets complicated is when the installer stuffs everything into the teeny tiny closet, and we can't see anything.

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Originally posted by kurt

You don't have anything on the concrete, i.e., no finish flooring?

And, what's your heat source?

Oh, sorry - misunderstood the first time.

Ceramic tiles in bathrooms. Carpet. Floating engineered hardwoods in Kitchen, Hall and Office. Hardwoods are performing tremendously BTW.

Heat source? Thought is was clear before. Its a natural gas on-demand tankless heater. Its the small white box on the high part of wall at the upper left of the first set of photos.

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Heat source? Thought is was clear before. Its a natural gas on-demand tankless heater. Its the small white box on the high part of wall at the upper left of the first set of photos.

Oh yeah; duh. I got so into your heating system, I forgot what the thread was about....

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