Navien Tankless Water Heater Comments and questions

Discussion in 'Tankless Water Heater Forum' started by willl, Dec 28, 2008.

  1. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    A indirect can never be confused with a tankless as being the same.
    Get the meaning of the word tankless? It means less tank.
    An indirect water heater is a storage vessel with an indirect means such as a coil or tank-in-tank that heats the water indirectly from an external source, such as a boiler.

    Tankless holds no appreciable measurable stored water and have their own burners, heating as used.

    Certainly as indirect tanks dump their water and depending on the BTU input of the indirect heat source, it can approach near instananious heating of DHW based on flow and input, but still not entirely the same.

    No confusing the 2
  2. MechGuy

    MechGuy Plumber @ Mechanical Contractor

    Messages:
    9
    Location:
    Iliinois
    Why not

    just burn your house down to heat water?
    You all keep sticking your heads up your arse and relying on cheap NG and Petroleum prices (under $12 for propane) and by the time you realize what hit you you'll be Arab Camel dung.
    And by God , thank God, in America we have the right to be just as stupid as we like.
  3. Dana

    Dana In the trades

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    Location:
    01609
    Methinks it's YOU that just doesn't get it- a Buderus & indirect isn't very much like a tankless AT ALL! (How do you figure? Just because it's low mass & wall hung?) It's far more similar to a standalone tank, just one with (typically but not always) more burner behind it (and lower standby loss on the tank itself.) And so what if it needs a tempering valve? (In MA where I live tempering valves are required for standalone tanks too.) With enough heat exchanger in the indirect you need not maintain the indirect storage above 125F anyway (although there may be valid efficiency reasons to let it run higher to get longer burns out of the boiler.

    Boiler + indirect vs. standalone tanks is more like apples vs. pears. If there's a pomegranate in the mix of choices it's the tankless, not the indirect. The near-zero thermal mass & inherent short cycling of the tankless make it distinct from the others.

    But you correctly state the obvious when you assert that no conventional standalone tank delivers 250 first-hour gallons (which takes ~150kbtus of storage + burner-output to pull off.) IIRC there's at least one condensing tank that can deliver it though (at a price.)

    And the boiler + indirect is usually the net efficiency winner, since tankless units never actually meet their EF numbers in residential apps (due to the effects of short cycling on low volume draws). High mass boilers may have lower-than tankless summertime HW heating efficiency, but during the heating season it's right up there, and increases the AFUE of the boiler by a significant amount if properly designed & controlled. Low mass boilers (and tankless units configured as boilers) will beat standalone tankless units on efficiency for just DHW when coupled with an indirect, in most residential apps since they can't short-cycle, and have extremely low standby losses compared to standalone tanks.

    Since you seem concerned about the equipment cost factores, calculate this: Using a cheap ~82-84% efficiency Takagi instead of a Buderus as a boiler, with a ~$1000 reverse-indirect acting as a heating system buffer & hotwater heater it'll meet-or-beat condensing tankless real-world efficiency(!) at hot-water heating for less than the in-the-crate cost of a condensing tankless (or a Buderus without the indirect).

    BTW: Who the hell really NEEDS 250 first-hour gallons in a residence, anyway? :) Lessee, the teenager is taking an endless shower while mi esposa is fillin' the soaking tub, and I want to clean up... I s'pose it's theoretically possible. But 250gallons/hr is like having two full showers going for that full hour. I might be able to pull that off with my system AND heat the house at the same time due to the drainwater heat recovery returns, but probably not in tub filling without tweaking the primary loop flow in the system, and even then it'd be marginal- at highest modulation you only get ~150KBTU/hr out of a Takagi T-KD20. But with the kickback from drainwater heat recovery, at full flow in a dual shower condition it's apparent-output would be over 200K.

    Also, you don't need expensive radiant for radiation to pull off an efficient combi design- coils in air handlers are easily up to the task. (Indeed that's my "hail mary" second stage heat for extended design-day heat load periods &/or setback recovery on my staple-up.) There are many ways to slice the combi-apple without spittin' pomegranate seeds.
  4. Runs with bison

    Runs with bison Member

    Messages:
    897
    Location:
    Midwest
    Bullshit. I keep seeing this claim but it isn't true.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,331
    Location:
    New England
    Where I live, you are required to have a tempering valve on the output of the WH. Now, that doesn't say where you have to have it adjusted, just that you must have one. Unless changed, they normally come set at 119-120 degrees. I run my tank at 140, but have the boiler set to allow it to cool off more before it rewarms it. Often, with no use, it may not need to fire for a day. Adds to the efficency, especially in the summertime.

    Now, I started a whole bunch of comments when I threw in an indirect. I know it isn't a tankless. But, I was responding to a comment that said you can't get a tank to provide 250 gallons the first hour. To that comment, BS! There are lots of tanks that can do that. Now, is it reasonable or economical, that's another story altogether. But, with a decent sized indirect tank (mine's 60-gallons) vs a typical tankless, you can get UNRESTRICTED FLOW at all locations at full output temperature that would take a VERY large tankless system, especially where I live in the winter. I can be filling the tub, washing clothes, running the dishwasher, and have someone washing hands, etc. all at the same time and have full use of the hot water. I've measured my inlet water at 33-degrees in the deep of winter. So, depending on your circumstances, there are good reasons to avoid a tankless. Now, again, lifestyle comes into play here, and I'm not going to comment on that and about how spoiled we are. Also note one of the comments on tank verses tankless are the standby losses. The tank I have is rated at less than 1/2-degree per hour of loss. So, if the power was off for a day, it still may not trigger the boiler to come on, if it could. If you were quick, you could probably get a few days worth or hot showers out of it without power. Try that with your tankless! A normal gas-fired tank would lose a lot more, but it's still not horrible. Fired by a mod-con, my system is rated at 94%. Since it modulates, and it is sized to be able to provide about 1/3 the normal design day needs at low end, it can run at barely 'idle', but ramp up to what's needed on a cold day, or to reheat the tank. Not all mod-cons have as large a modulation range. The tank is SS, and should outlive me. Expect the boiler will need replacing before the tank, but the guts are SS on it, too.

    If you have a boiler and aren't using an indirect, I don't think you're being very efficient. If you live where the incoming water doesn't get really cold, a tankless has some benefit. If you don't want to put up with variable water temperatures, no hot on a low flow use, or need a high flow rate, then avoid a tankless. It can be set up to overcome that, but it gets more complicated, and a boiler may be a better choice. Ganging tankless units to get high flow is quite expensive in both the infrastructure (large gas lines) and available combustion air and flues. In some places, your no-use gas charge is based on possible demand, so you're paying more for gas, even when you aren't using any.

    So, pick your poison, understand the benefits and limitations of the choices and make an informed decision. My energy use compared to my neighbors is about 1/3 less, and is without compromises they have. People can shower one-after-the-other all day.

    A boiler is going to require less service than a tankless system since it is using less 'fresh', mineral laden water, so there'd be little scale. An indirect doesn't see high enough temperatures at the heat exchanger to precipitate out any amount of mineral deposits, so efficiency should stay reasonably constant. On a tankless, the goal is to heat the potable water very fast, and you'll get the mineral deposits (unless you also have a softener).

    No one system is 'best' for everyone. Pick the best for your circumstances. To exclaim only one choice is viable is not taking into the whole account of use patterns, volumes required, existing equipment, tolerance for restrictions, and amount of money you wish to spend. Energy costs here may approach many other country's, but only if the tax rates go up. It costs the Europeans about the same for gas as here, but their taxes are MUCH more. There should be a move to make things more efficient. This is a good thing, but you have to weigh the costs/benefits. We could all drive mopeds and get 70mpg, but it just wouldn't be the same...not one answer is best for all.
  6. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    Wow did this take a derailment off course of the title post (Navien)
  7. Ladiesman271

    Ladiesman271 Homeowner

    Messages:
    221


    It depends on where you live.

    "The standards apply to every owner-occupied or rented dwelling, dwelling unit, mobile dwelling unit or rooming house unit in Massachusetts which is used for living, sleeping, cooking and eating. Dwelling unit shall also mean a condominium unit. These regulations have the force of law. Local boards of health have the primary responsibility for their enforcement."

    and

    "Hot Water Facilities

    Facilities for the heating of water must be provided (i.e. supplied and paid for) and kept in good working order by the owner. The owner must supply hot water in sufficient quantity and pressure to satisfy the normal use of all plumbing fixtures which generally require hot water to function properly. The temperature of the hot water is not to exceed 130° Fahrenheit (54° Celsius) nor fall below 110° Fahrenheit (43° Celsius). Under certain leases, an occupant may be required to provide the fuel for the heating of the water. [410.190]"



    http://www.sec.state.ma.us/cis/cissfsn/sfsnidx.htm



    .
    Last edited: Dec 9, 2009
  8. Ladiesman271

    Ladiesman271 Homeowner

    Messages:
    221


    The majority of people have no need for a boiler installation, so what are those people supposed to so? I have a forced hot air system, so I use a furnace for heat. That leaves a tank or tankless for domestic hot water.

    You also forget to mention the installed retrofit retail cost of a modulating boiler, vent system and indirect tank. A tank type water heater is way less expensive than that setup. A tankless water heater will also be less expensive.

    Note that my tankless works fine during power outages.
  9. Dana

    Dana In the trades

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    Hey, jadnashua- I don't care WHAT your boiler is rated, it's giving you nowhere near 94% when heating the indirect:



    Indirects don't stratify enough to give you 100F return water to the boiler from the heat exchanger coil in the indirect if you're running normal DHW temps. If you're letting the indirect drop as low as 120F you might hit 90% combustion efficiency at the beginning of a burn not more. By the time it's back up to 140F it's more like ~85%. (And that's just raw combustion efficiency at the boiler's heat exchanger, where 10-15% of the energy has gone up the flue, not total thermal efficiency of the hot water heating system, which is boiler, indirect, & plumbing-insulation dependent. You WILL have other losses.)

    Condensing tankless units run higher efficiencies because the incoming water is typically well-under 70F, but they give up a lot in short-cycling. In real-world use they're similar to mod-cons with indirects kept at lower storage temps like yours.

    But the rest of the arguments you're making ring true. If you got 150K+ output at the boiler and an indirect that can use it, you can indeed get your 250 first/second/third hour gallons out of it. (For what, we'll never know! ;-) )
    Last edited by a moderator: Apr 28, 2013
  10. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    Good points Dana,
    All similar for the folks that install modcons on baseboard or whatever and run the temps right up to 180 all heating season with elevated return temps.
    They could have saved money and put in a less expensive boiler and achieve near equal efficiencies.
  11. Dana

    Dana In the trades

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    3,028
    Location:
    01609
    If they fit the outdoor reset curve reasonably, even a 180F design day temp requirement it can run at condensing temps much of the season. With better load modeling it could run lower temp MOST of the season (but that level of sophistication isn't likely to be used in a residential app, and the setup costs would be ridiculous.) Design day temps represent less than 3% of the hours in heating season, and a small fraction of the actual fuel burned. But even on the afternoon of design day it's not unusual to have a heat load that's less than 15% of what it was in the bitter pre-dawn hours. The modulating factor alone (even when not condensing) produces very real fuel savings, just not nearly what it does when in the condensing zone. Anybody who runs baseboard at fixed 180F temp with a mod-con is throwing away money (double-digit percentages of the total heating bill.) Since they all come with outdoor reset built in, I can't imagine why anybody WOULD run 'em at 180F??

    Still, it's not always worth it to go mod-con. If you get the total heat load low enough it's hard to rationalize the expense even WITH low-temp radiation. I never need more than 130F heating water at my place but:

    A: "right sized" mod con for my actual design day heat load doesn't exist, and

    B: The smallest mod-cons might still do OK for heating, but would be marginal for my peak DHW loads without a large indirect.

    C: A mod-con would save me at most ~100 therms/year over running the whole shebang combi-mode with the $500 tankless (or was it only $400? I forget- but it was cheap) plumbed as a boiler, and a reverse indirect, with burner to spare on the DHW front. The fact that a tankless modulates and is very low mass makes it easy to design a system that maintains near-maximum operating efficiency on the tankless, especially when combined with the thermal mass of the reverse-indirect plumbed as a heating buffer (not a heating zone.)

    Since I need to maintain an indirect at ~125-130F for DHW anyway, I'm already suffering that standby, and the financial benefits of going with lower radiation temps are marginal, it was easy to head toward the buffered combi solution, if not the mod-con. Until/unless NG gets a WHOLE lot more expensive I'm not likely to swap in a mod-con. But if/when it does, the system as-is runs in the condensing zone for majority of the burn time, and well into condensing on heavy DHW draws, but still over 100F. With a mod-con it would realistically get 90-92% efficiency as-is, and I could reconfigure it slightly and probably squeak another percent or two out of it in heating mode but again, the difference in annual cost even at 4x the current fuel price wouldn't necessarily make it worth the effort to make those changes.

    But that's my situation- YMMV.

    Still most homes in the US have design-day heat loads well under that of a tankless, and peak DHW loads well OVER what a perfectly sized boiler for heating will deliver. The answer to making them both maximally efficient is usually mass, and combining the thermal mass for both DHW and heating buffering is something that SHOULD be done more often that it is. Modulation has it's limits- the most you get out of residential sized mod-cons is about a 5/1 turn down ratio, (most are around 4/1). The real difference in LOAD is more than 5/1 on every day of the heating season, but with sufficient mass cycling losses can be minimized even with fairly oversized boilers.
  12. AAnderson

    AAnderson In the Trades

    Messages:
    36
    Location:
    Aptos, CA
    Back to the original question. With many of these in place now, I feel they warrant the slightly higher cost than the others if recirculation and the stainless steel heat exchangers are the consideration. The leak detection is a great feature. They are how ever more complex than the others.
    The problem Navien and any other manufacture's have to over come except Rinnai (who has done a great job) is service and has is to create a national service program.
    When CEC imported and distributed Bosch, you couldn't ask for better technical support. When Bosch acquired CEC, they seemed to completely down play service, maybe not understanding the north american market. the fast development of new products, lack of parts and support killed them in their tracks, for now. the B series is bullet proof and no one has anything like Bosch's H1600. The 2400 and 2700 series are a mile stone and all Bosch has to do now is build confidence back because these are both superior units. Bosch's C800 condensing is also a worthy contender. Rheem's ECO line holds its own.
    What matters at the end of the day is service and not just calling customer support but someone local who knows the product, has the experience and can take care of the problem and you just can't do this over the phone. When the customer has no hot water and you have to wait for parts to arrive, the customers experience with a tankless goes south in a heart beat.
    If auto manufactures treated repair and service the way most tankless treat service, we'd be riding horses.
    Who has the greatest influence on a purchase in my experience, the plumber, for better of worse. All manufactures need to increase training of installers and service personnel. If we were trained as plumbers the way manufactures train installers, we'd still be in the 18th century. I've sat in on too many late afternoon installation classes where the trainers have flown through the material and lost most after 5 minutes. Training should be a day long affair, not an hour or even two and include live fire, practice an installation and at least some limited trouble shooting to understand problems due to short sided installations.
    Tankless is clearly hear to stay and the old excuse for using tanks is in the history books. Does anyone still install galvanized water piping, no! Are homes built with cast iron waste except in the second story, not many.
    When I first started Plumbing in the 1970's, there were still lead closet flanges that had to be repaired, 7 gallon wall hung with 14" rough bowls were still in use. I remember working on a Rhuud water heater that was copper tank with rivets from the 20's with gas and air levers for adjustment.
    I still have my roughly 60 caulking irons and asbestos Italian runners for lead work when I first trained and my gas torch and lead pot. Who would have thought of a fraction of the tools and materials now available much less micro chips on a water heater? To sit and deny what is changing is a fools death. Tankless is here and not going away and more manufactures will enter the market. How they treat plumbers and service personnel will influence who will be around at the end of the day...
  13. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    Having taught plumbing and heating classes, you can't teach common sense nor, preach anymore than we can how important it is to read and follow the installation manual. If a "installation tech" comes to an advanced class we should be able to assume they understand gas piping, venting, power and controls. That's where we lose them in the first five minutes.
  14. AAnderson

    AAnderson In the Trades

    Messages:
    36
    Location:
    Aptos, CA
    In my area, most that attend installation classes have never even opened a code book, read gas charts much less understand how to calculate for them. I have yet to see another plumber who owns, much less use and understand a manometer or a digital multi meter. Manufactures have a large gap to close as do plumbers too.
    California does not require the individual to hold a license or training certificate but the plumbing contractor must have 4 validated years and pass a test, have a bond and insurance. I worked for the state contractors board to help re write the test in an attempt to stave off the contractor schools from selling answers. We are sadly behind many other states in this regard.
    I just happen to have a background that has involved build desalination equipment world wide and have taken AC/ Dc theory, motor controls, designed and built water, waste equipment and fluid processing equipment and happen to have a degree in mechanical engineering/
  15. happy

    happy New Member

    Messages:
    1
    Location:
    Colorado
    Happy owner

    I live in Colorado at 6200 feet elevation. I have a Navien Tankless hot water heater and I am extremely satisfied with it. The 12 year waranty on the entire unit is the best in the industry. They may be made in Korea, but that country is one of the coldest climates in the world (in winter) so they got it "right" in their own country before shipping it to the U.S. I don't know how tough it is to find a trained tech to do the installation in your area. You might want to check their website. But I really appreciate being able to use PVC instead of stainless for air intake and exhaust. That saved a bunch of bucks. It easily services 2 simultaneous showers.
  16. Dana

    Dana In the trades

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    3,028
    Location:
    01609

    :) :) :) :) :) :)


    That's pretty funny- of the many places I've spent whole winters, I'd be hard pressed to say Korea was even in the coolest five. Seoul's heating season is only ~5000 HDD, well below most locations at 6.2K' in Colorado. See:

    http://kgeography.or.kr/publishing/journal/15/02/01.pdf


    (If you can't read Han-gul, there are some koringlish bits toward the end. Heating degree data are presented in celcius. Multiply by 1.8 to come up with 'merican degrees. )

    BTW: Were/are there any alitude adjustment tweaks made to optimize it for 6.2k' elevation? Very few populated places in Korea are that high- not sure if they thought to design it in...
  17. Gary K

    Gary K New Member

    Messages:
    4
    Location:
    Burlington, Wa
    Navien Installs

    I have personaly installed over 50 of these units, I have the new NR-210A in my home for testing. There are pros and cons to every brand of tankless including Navien. Bottom line Navien delivers what is promised,

    My Web SiteMy Web Sites BlogMy Personal Photo Site
  18. Donald

    Donald New Member

    Messages:
    1
    Location:
    Big Bear City
    navienNR-240A

    Was installed by plumber in area and It runs all night and keeps me awake. Live in big bear city 7000 ft. altitude. is there any solution?
  19. Dana

    Dana In the trades

    Messages:
    3,028
    Location:
    01609
    By "runs all night" I presume you mean the blower never stops after the flue purge, in which case there's something defective on the control board or a sensor. This is one to run by a Navien trained tech, but it may be diagnosable via phone. Have you run it by the installer?
  20. ionltd

    ionltd New Member

    Messages:
    12
    Location:
    Illinois
    We just had a Navien installed last week and what a HUGE mistake!

    It took 2 guys (plumbers) almost 12 hours to install, but that would have been fine if had turned out to be everything it had been touted to be.

    First of all, it takes over 2 1/2 minutes of running full blast to get hot water to my kitchen sink. When I asked the owner of the plumbing company he said, "Yea that's normal"

    Then I asked him why was there this weird noise every time we turned on the hot water? A noise that shakes the whole house? (Pause while he's thinking "lady you're a nut") Then he says "never heard of that before.

    Then I explained that since we live in the country and have well water, that to get any type of water pressure we had to turn both the hot and cold faucets to full when bathing. If not you would get a drip bath. He said they didn't want to turn the temp past 130 because of scalding reasons.

    I've run my dishwasher twice and noticed things not getting clean like they did with our old water heater.I don't want to blame this on the tankless yet, but give me time.

    Washing your hands, or washing dishes by hand is useless unless you don't mind cold water or don't mind chancing running your well dry by leaving the faucet running for 20 minutes.

    How many of you professionals would have recommended a tankless water heater to someone on well water? Just curious.
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