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Thread: Eternal Hybrid Water Heater

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    DIY Junior Member austintx's Avatar
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    Default Eternal Hybrid Water Heater

    I am considering one of these Eternal Hybrid Water Heaters http://www.eternalwaterheater.com/ to replace my 17 year old tank heater and wanted to know if anyone has any experience with these. Now, before anyone jumps up and says "just get a Rinnai because this won't save you any money" or "tankless sucks" or the like, let me explain what my goals are and why I think this is the best option for me, I would be more than happy to entertain alternatives if they can meet my requirements.

    I have a small ~1200 sq ft house, 3 bed, 2 baths, no jacuzzi tub or anything, one bath with a standard tub/shower, the other (one day, when I finally finish it) will have a shower only. Space is a premium in my house, so I would like to move the water heater into the attic. So that rules out most tanks.

    Freezing is not much of a concern as I live in Houston. Most of the year it is hot, a couple months are pleasant, a couple of weeks are getting chilly (~40) and *maybe* a couple of days where it dips into the upper 20s for a few hours.

    Next issue is our new front loading washer fills using brief spurts of water. From what I have found from searching around is that it causes a tankless to cycle on/off but is never on long enough to actually add much heat to the water.

    Currently, the tank is in the utility room, which is in the center of the house. By moving it into the attic, it will be above the utility room, so there will only be a maximum of about 10 feet of pipe between the heater and the washer.

    As far as I can see, the hybrid heater is probably my best option, but would like to know if anyone has experience/opinions on them?

    Thanks,
    Austin

    Last edited by Terry; 02-24-2011 at 03:30 PM.

  2. #2
    Master Plumber master plumber mark's Avatar
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    Talking they are supposed to be pretty good

    never installed them but I have heard that
    they were pretty good...

    one thing that scares me is in Houston yourattic could reach temps of at least 145 during the summer....

    I dont know how much that heat the computor circuit board on that unit can bear.....

    you might want to call and find out about that


  3. #3
    DIY Senior Member zl700's Avatar
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    Did you get a price quote yet?

    I don't wish to open up the argument of payback, but from what I understand the Eternal is $1500 over a tankless so comparing tankless to standard tanks, and then the eternal what is your payback now?

    Let us know how it goes, especially if you get the eternal. Its my understating the unit works real well till the hybrid tank depletes, then its no better or worse than tankless, especially regarding flow rates/temp rise. This perhaps is not a factor for your home with no tub or big draw demands.

    You make a good point about tankless and front loader washers. Mine for instance probably never fills with hot water given the fact that my tankless will fire on fill but is so far away, the hot water barely makes it there. Unless I have run the dishwasher or kitchen sink, I'm lucky if my hot water cycle is luke warm. I don't wish to recirculate, I don't have access to pipes to insulate or install a return either.

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    In the trades Dana's Avatar
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    A tankless 10' away would definitely heat the water to the washer in those 2 quart spurts, but at ~50% efficiency or less. (Half the heat is blown away in the flue purge & ignition cycles on ultra-short draws.) But the average efficiency will be much closer to the EF rating of the tankless, since the largest volume would be showers/baths, at which point it's running at about it's EF rating efficiency. (If 20% of your water use is at 50% efficiency, and the rest is at 82-84%, you're still doing pretty well on average.)

    At tankless in series ahead of a tiny electric tank would deal with cold-water sandwich issues and guarantee you never get tepid water for your washer. This is a standard hack (recommended by Bosch, which has some pretty crummy low-end tankless units in terms of startup time and low-flow characteristics, IMHO.) The Bosch Ariston 2.5 gallon electric mini-tanks are pretty good for this application though, with only ~20-25kwh/month in standby loss. If the cold-water sandwiches on the short bursts are long, bringing the mixed temp in the minitank unacceptably low (which isn't all that likely with a Rinnai or Takagi) raising the temp of the output of the tankless and a tempering valve on the output of the mini tank fixes it.

    Where space is at a premium in a low freeze risk location, locating a mini-tank above/behind/beside the washer (the tiny Arisotn is about a 14" cube- probably fits under the washtub), in combination with an outdoor tankless like the Rinnai V53 (or even a monster-burner Takagi TK3 OS) would be roughly half the money. That combination delivers ~75%+ as-used efficiency compared to ~85%(on it's best day) for the Eternal unit, but for the difference in cash you'd get better payback out of a drainwater heat recovery system on your shower (requires at least 3' of vertical drain below the shower- 5' is better, tough to implement in slab-on-grade) or a small batch-solar pre-heater on the roof and get 3-5x the return on investment.

    The payback in fuel/utility savings between a $500-1000 tankless + $150 minitank and a $2300 Eternal the for a 2-3 shower/day EnergyStar washer/dishwasher family will be approximately never- longer than the anticipated lifetime of the unit. (If you're running a small commercial laundry or a car wash, or have an 8 person family, now you're talking!) In warm-water Houston you'd be using less than 150 therms/year with the lower efficiency unit. The Eternal would save you 15-25 therms/year + 150kwh/year best-case.

    Drainwater heat recovery reduces the total energy used for HW by ~20% (for most families- more for families where showering is more than half the HW use), at a cost of $500-1000. This a better performance boost than a higher-efficiency heater. A 20 to 30 gallon batch solar pre-heater would cut annual fuel use for HW heating by 30-50% (or even more) in Houston, (and dramatically raise the temp of the "cold" in "cold-water sandwich" for a completely tankless situation) for about $1000-1500 in hardware (not counting any kick-backs you'd get from tax & utility type incentives.)

    Every situation is different, but were it me, I'd be looking at an outdoor tankless + batch solar before going for highest-efficiency hybrid/tankless. If you have the roof space and can stand the look of the thing on the roof (batch heaters come in both flat-panel or better freeze protected but klunky looking evacuated-tube + header tank versions. Either are fine for Houston weather- tubes will give you better winter performance but are more likely overheat in summer. Smaller is better from a system simplicity POV.)

    And an unconditioned attic most likely WILL create an absolute operation temp or lifetime degradation issue for the electronics on the Eternal. If you go that route, the attic probably needs to stay under 120F for the thing to survive more than a decade.

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    DIY Senior Member Runs with bison's Avatar
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    Having lived in Houston, the tapwater temperature tends to be lukewarm and the houses are typically slab. How do they configure drainwater heat recovery installs for that?

    Houston is nearly ideal for solar water heating.

    I share the concern about the longevity of the circuit boards in a hot attic space with the long Houston summer. Of course, the houses I experienced in Houston had their furnaces and blowers mounted in the attic so I guess one should expect about the same sort of lifetime as those.

    I'm not sold on tankless because of several drawbacks, but I'm stuck waiting for the various condensing tank water heaters to come out and establish themselves on the market. The pricing at present is a bit rich.

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    In the trades Dana's Avatar
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    Yeah, like I said "...requires at least 3' of vertical drain below the shower- 5' is better, tough to implement in slab-on-grade...", making it a non-starter for lots of folks in Houston.

    But simple in-line batch hot water takes up no interior space, and is a relatively cheap install (cheaper than installing the Eternal). Condensing HW heaters would have to get a LOT cheaper to compete on a price/performance basis in places like Houston.

    Condensing HW heaters may have some reasonable return when used in combi systems for both space heating & DHW, somewhat comparable in price/performance to condensing boilers. For strictly DHW use, not so much. It takes a lot to make up the up-front difference in performance between standard-efficiency tankless vs. condensing. In rare instances the cost of the stainless vs. PVC venting is enough to tip the balance though.

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    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by Dana View Post
    Condensing HW heaters may have some reasonable return when used in combi systems for both space heating & DHW, somewhat comparable in price/performance to condensing boilers. For strictly DHW use, not so much. It takes a lot to make up the up-front difference in performance between standard-efficiency tankless vs. condensing. In rare instances the cost of the stainless vs. PVC venting is enough to tip the balance though.
    I doubt that. I don't see combi as necessary for one and it's just a matter of time before storage condensing becomes commonplace and prices drop. Energystar guidelines will drive that way in the coming years from what I've read of their direction. The current units tend to be high firing rate overkill at about 2X cost. That is not the most cost efficient way to design them. Heck, from watching my own low efficiency unit I believe I could turn it into a partial condensing unit with some minor mods. I've seen it operate in that mode and I've designed/done troubleshooting/redesigned more challenging heat exchange equipment and reactors.

    The tankless problems don't appear to be entirely fixable from a technical standpoint. Other than high fire rate continuous applications, tankless will have an inferior performance to storage...unless it incorporates various storage aspects. Efficiency will be higher with condensing tankless, but the user experience of condensing storage will whip it handily. In the end tankless becomes a niche product, the undisputed best option for those that accept the necessary compromises.

    That's my murky crystal ball.

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    DIY Junior Member austintx's Avatar
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    Thanks for all the replies! I have been without a computer all weekend or I would have responded sooner.

    I have not received a price quote yet, but from what I could find on google, they seem to go for about $500 over a decent traditional tankless (for the unit only) I figure subtracting out the $200 or so for the stainless flue that many tankless require (the eternal can use PVC) and it isn't a huge price premium.

    Although it gets very hot here in Houston and my attic is unconditioned, I have been up there on a hot August day and lived. It does get very hot but I doubt it gets above 120. About 90% of my roof is shaded by a couple of large oak trees, which would also rule out most solar options. My furnace is also in the attic (basements are a rarity in these parts) and it has survived, but I know it doesn't have much in the way of complex circuitry.

    My two biggest concerns are performance and space savings, as long as it doesn't cost more to run than my old tank, then I am happy. My current tank is natural gas as well. Either way, I don't think I would ever see much return on investment by going tankless or hybrid, but I am willing to pay a bit of a premium to free up that space in the utility room.

    The tankless+mini tank sounds like an interesting option as well. I only see the short cycling of a tankless being an issue for the washing machine, so I could see the mini tank being needed just for the washer.

  9. #9
    In the trades Dana's Avatar
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    Quote Originally Posted by austintx View Post
    Thanks for all the replies! I have been without a computer all weekend or I would have responded sooner.

    I have not received a price quote yet, but from what I could find on google, they seem to go for about $500 over a decent traditional tankless (for the unit only) I figure subtracting out the $200 or so for the stainless flue that many tankless require (the eternal can use PVC) and it isn't a huge price premium.

    Although it gets very hot here in Houston and my attic is unconditioned, I have been up there on a hot August day and lived. It does get very hot but I doubt it gets above 120. About 90% of my roof is shaded by a couple of large oak trees, which would also rule out most solar options. My furnace is also in the attic (basements are a rarity in these parts) and it has survived, but I know it doesn't have much in the way of complex circuitry.

    My two biggest concerns are performance and space savings, as long as it doesn't cost more to run than my old tank, then I am happy. My current tank is natural gas as well. Either way, I don't think I would ever see much return on investment by going tankless or hybrid, but I am willing to pay a bit of a premium to free up that space in the utility room.

    The tankless+mini tank sounds like an interesting option as well. I only see the short cycling of a tankless being an issue for the washing machine, so I could see the mini tank being needed just for the washer.
    Including the mini with the whole hot-water feed to the house will cure some of the most annoying aspects of tankless systems: The "cold-water sandwich", and flame-out on dribble-draws:

    When draws are intermittent & short the ignition & flue purge cycles on the tankless inserts slugs of cold water between sections of hot water in the distribution plumbing, so the water at the tap runs hot, then cold, the user turns up the hot just about the time that the next burst of hot arrives, backs off just in time for the next coldwater sandwich, repeat... With a mini tank in series with it the coldwater sandwiches mix in the tank, temperature shifts related to them ramp slowly enough to be imperceptible.

    When the flow of water is so slow that the lowest modulated firing rate of the tankless still takes the temps too high the tankless protects by turning the flame off. So in slow hot water rinses it starts out warm, gets hot, the user turns down the flow & mixes in more cold, then suddenly it's all cold. Once again, having even a couple gallons of storage keeps these marginal firing rate goings-on imperceptible to the user. (While there is a tendency to look for the maximum firing rate gpm specs, in warm water areas one that goes lower is better. Sub-20KBTU/hr for a min is good, sub-15KBTU/hr is better. But with a mini-tank in series you won't really care what it is.)

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    DIY Junior Member austintx's Avatar
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    Starting to toy with the idea of using a mini tank+tankless...Are the Bosch Aristons the most common/best choice for mini tanks? Also, from my limited research, I would need to with Ariston GL6, because it has 3/4" inlet/outlets, to not restrict the flow as most tankless heaters use 3/4" inlets/outlets as well (for whole house use)

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    Smile Grand Hall Factory

    Quote Originally Posted by zl700 View Post
    Something to consider;
    The Eternal Water heater was manufactured under contract by Grand Hall, a US gas grill distributor with a overseas manufactuter for relabeling. After the contract for 1200 units is met, who will make it next and for how long?
    GrandHall is the manufacturer for the Eternal Water Heater and there are no plans according to the factory to stop making their product. I research Grand Hall and found that they are state of the art when it comes to Stainless steel manufacturing and the Eternal Water Heater is state of the art. I have installed some of their units and with a 20 year waranty and the amount of hot water, it's hard to go back to anything else.

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    Plumber @ Mechanical Contractor MechGuy's Avatar
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    Quote Originally Posted by zl700 View Post
    No, they are made under contract with a company in Taiwan and are sold here in the US by a marketing company called Grand Hall.
    Alright, let's start from the beginning. Grand Hall is a Contract Manufacturer of Gas Grilles for Sears, Char-Broil, Weber and a few more.
    They've expanded to make Hybrid DHW under the Eternal name and eventually sell Grilles under their own label.
    They are HQ overseas in Taiwan and domestically in I think Garland TX.
    The 20 year Warranty on the units is for the HE only. The floor models are discontinued but the 145S/195S/M Wall Models are current.
    No matter how many times you say something different, the truth stands as fact.

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    DIY Junior Member timtheplumbingwholesaler's Avatar
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    Default Eternal Hybrid

    I have been in the plumbing wholesale business for 32 years. I have always been into new products and seen the benefits of the things I consider to change markets. Eternal Hybrid is the greatest product I have ever seen towards changing the standards. We have sold over 100 units since we have taken the line on, and have had only two warranty issues of which Grand Hall stood up and took care of. Now as far as the buy sell contract, it is not true. Grand Hall is in the stainless steel business, and they have sold outdoor kitchens and BBQ pits for a long time. I am not fearful of this great product not being available, as to the investments of research and development and all the code approvals required makes me know they will be in this for a long time. I am a major water heater dealer, selling the State label from AO Smith. There are many fine products that they offer, and we will continue to sell their product. I also am a Noritz distributor, and do a great job selling those instantaneous heaters. I believe in green and I believe in saving money. Now, let me explain what facts I know on the Eternal Hybrid and why it has no competition. If anyone has ever studied this product,

    1. The single greatest advantage of Eternal Hybrid Condensating Water Heaters is no pressure drop. All instantaneous heaters limit the flow by electronic valves to maintain the constant temperature except Eternal Hybrid as the demand increases. Eternal allows full flow with minimal pressure drop. It actually holds the water at higher temperature than needed, then mixes the water on the outlet with cold to maintain a constant temperature and pressure.

    2. Although the unit pricing is more expensive for the Eternal Hybrid up front, the the total installation cost is about the same, because Eternal Hybrid does not need by pass valves or isolator valves, it uses PVC venting, and has near zero CO emissions.

    3. Eternal Hybrid weighs 95 lbs and can be installed floor or wall mounted. It has top connections for water inlets, and it is by far the neatest looking unit made. The competition cannot compete with the functionality or the efficiencies of this unit, so they will have to quote some other problem they foresee because they have no answers to the truth.

    4. Recirculation pumps does not require a tank to store water in. It has a 2 gallon storage. It works perfect as is for looped systems. We have changed out several restaurants here in the City of Houston with 100% success rate of taking out 100 gallon storage with 199,000 BTU heaters and putting the Eternal Hybrid in. We have take photos of these change outs, and every single one of those installs has left the customer extremely happy.

    5. At 98% efficient, I don't have to say more, with the exception, that without condensation, water heaters cannot be that efficient. Eternal condensates faster than instantaneous heaters, and does not need the flow that the instantaneous heaters need to make the burner engage. Since there is a two gallon storage, Eternal Hybrid can deliver hot water without having to engage the burners if needed. On instantaneous heaters they have to at least hit 1/2 GPM in order to start up.

    6. YOU TUBE has several videos to show the demonstration of many of these points and more. One of the greatest points is the 20 year tank warranty on residential, 10 year on commercial. Another is there is no sediment buildup in the unit where on instantaneous you will have to flush these units out. I have many more points, and you guys that have no better selling feature than to say after 2500 units are made what is going to happen... Well, I have sold a lot of units, I promise that point is dumb. They are the same company and I right my Checks to Grand Hall.
    2.
    Last edited by Terry; 04-20-2011 at 08:16 PM.

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    In the trades Dana's Avatar
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    Quote Originally Posted by timtheplumbingwholesaler View Post

    5. At 98% efficient, I don't have to say more, with the exception, that without condensation, water heaters cannot be that efficient. Eternal condensates faster than instantaneous heaters, and does not need the flow to make it happen. Since there is a two gallon storage, Eternal Hybrid can deliver hot water without having to engage the burners if needed. On instantaneous heaters they have to at least hit 1/2 GPM in order to start up.
    Gotta call BS on that one, Tim. To hit 98% even as a raw combustion efficiency the temp of the water entering the burner has to be well south of 90F. It absolutely DOES need flow for that to happen, since the coldest water in the tank during a temperature-maintenance-only burn is well north of 100F. The steady-state numbers can only be met with a constant flow of sub-75F water.

    That's not to say that it's isn't a superior design, only that there's no way kind of efficiency numbers you're talking at no flow. They don't have license to violate the laws of physics concerning the dew-point of natural-gas exhaust, and how much of the heat of vaporization is retrievable at what temp. It takes ever lower temps to wring the last 5% out of it, since the water vapor pressure of the exhaust gas is higher at higher temps. With 110F water in the bottom of the tank they'll beat 90%, but it won't hit 95%, let alone 98%.

    EF-test parity notwithstanding, if they've designed control algorithms correctly it should beat most condensing tankless efficiency in real-world use due to the buffering effect of the mini-tank. It won't/can't short-cycle losses on 1 quart draws the way a true tankless will, and it's pretty cheap & easy to insulate it to high-R. With the low surface area of a 2 gallon tank the standby losses will be small fraction of that of a standalone gas-fired tank. Some of the condensing tankless units with mini-tanks are probably pretty close to it in efficiency, even if they're kinda Rube-Goldberg-ish in design complexity compared to the Eternal. I'm betting there will be imitators of the Eternal design soon enough. I'd be interested in seeing 3rd parting comparison testing using other draw-volume & frequency profiles than the crude D.O.E. type EF test profiles though (which have traditionally exaggerated tankless efficiencies.)
    Last edited by Terry; 04-20-2011 at 08:17 PM.

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    DIY Junior Member BillyCrash's Avatar
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    Hello, new to the forum and found this thread. I'm in the process of building a new home, and my builder says I can upgrade to eternal from his standard application Rinnai heater for $400 per unit (I need 2 units). Do you think that is a reasonable upgrade cost, and that the breakeven time will be short enough to warrant the cost? Thanks!

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