Navien Tankless Water Heater Comments and questions

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

  1. Scott D. Plumber

    Scott D. Plumber In the Trades

    Messages:
    67
    JM, a few thoughts to ponder:

    How many Rinnai's do you install per year? Does not the Rinnai have better water temperature control and higher flow rates? Doesn't it cost a couple hundred bucks less and have better tech support?

    For efficeincy, if you have a car that gets 30mpg and one that gets 35mpg, and they are both in the driveway "OFF" which one is getting better milage?

    Now I get the PVC vent thing, however if the venting is up and out the Rinnai is still less expensive with an easy push joint vent kit and a much better hot water source. These things only run for minutes a day, the rest of the time they are off. I think 90+ is over rated for tankless. Seems to me that tgemperature control and flowrate matter more.
  2. Dana

    Dana In the trades

    Messages:
    2,805
    Location:
    01609
    80+ is (quite literally) overrated for most tankless in most installations due to the particulars of the EF test: 10.2 gallon minimum draws are nothing like real-world use, and the short-cycle losses for sub-2 gallon draws erodes efficiency dramatically. In real-world draw profiles 0.82EF type tankless units hit in the mid-70s, condensing versions scoring 0.90+ EF numbers run in the high-70s/low 80s. The higher thermal efficiency isn't worth (much) extra for. (Indeed, you'd get better return in fuel savings on drainwater heat recovery on the main shower for the price-delta on the high/mid efficiency units themselves, vent costs not included.)

    Steady-state thermal efficiency is a theoretical upper limit, but not a good measure of the real-world performance. Those with tight controls over flue purge cycles losses will do better than those that don't. Those with small header tanks to mitigate cold water sandwich issues that also inhibit fire when the header is above a minimum temp will also suffer fewer cycles, and thus lower purge-losses from multiple low-volume draws, etc. Steady state thermal efficiency or raw combustion-efficiency numbers are only relevant for very large or continuous-draw duty (pool heating, anyone?), not domestic hot water for typical household use. In space heating, commercial laundry/car-wash, health-club showers, or home solar-backup you might beat 90% with a condensing tankless, but not very often (if ever) in straight-ahead DHW apps.


    BTW: A a question for any of you who have taken (or will take) the tech courses from various tankless vendors: Is there a modulation level where they typically peak out on raw combustion/thermal efficiency? Do any vendors share any of that data?

    Condensing versions likely peak at lower fire in 25-35% of full-fire range (like most mod-con boilers), but I suspect the single heat exchanger types may do better at the high range (like copper-tube boilers), and may be under 80% for raw combustion efficiency at the low end of the modulation range, but 85%+ in the mid/high range. I could as-easily believe the designs have been tweaked to provide peak efficiency at some other burn level, but haven't been able to find test data (which I'm sure is quite proprietary when tested by the manufacturers). Can anybody either confirm/disabuse me of those guesstimates?
  3. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL

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  4. Dovels INC.

    Dovels INC. New Member

    Messages:
    7
    i have had nothing but problems with navien /// not the water heater but with the warranty /////david mills is a jerkoff and is the man incharge of warranty dont do any warranty work because you wont be reinbursed for your expences let them send there man from the factory so so he can fix it ////im not sure wich brand im going to but im sure i wont sell any more navien
  5. sounds litk you are not happy with navien


    I guess that you sell and install this brand??
    sounds like youi have been hung out to dry
    by their warranty department...

  6. Dovels INC.

    Dovels INC. New Member

    Messages:
    7
    i sold 22 units in the last 2 months im selling rheem now so let say navien is typical korean company that has great sales department and wont backup anything they say because they hate america and the american people. i told them to pack there shit and move back to korea
  7. 22 units in two months....

    you are doing pretty good....

    where do you reside in the USA...???

    I am going to send you a private message also...
  8. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    Oh come on

    A quick and easy D&B business search of Dovels Inc, returns it as one-man shop with maybe a helper

    22 units, sure!

    Sounds like a new installer to me that screwed it up

    Take his input with a huge grain of salt!

    I like all the Jap platform units with each one having it's better parts, but keep an eye on Navien, they didnt move to position #2 in North America recently in sales, behind Rinnai for no reason.
    Last edited: Aug 26, 2009
  9. Dovels INC.

    Dovels INC. New Member

    Messages:
    7
    im a 4 man shop and 22 units is not that many in 1 month. i own a business how about you. and i agree with most of the people on this forum about navien thats why im selling the reem tankless. wich is good because i also sell rheem heating and airconditioning.the only reason i posted here is so other businesses dont get taken by naviens warranty also most businesses go under for unbillable hours but if you own a business you know that
  10. Dovels INC.

    Dovels INC. New Member

    Messages:
    7
    lol zl100 sounds like a navien rep to me its funny when you tell a company that everbody is bashing them on the internet how defencive they get and navien dose have a good product just shitty customer service and if you are a business owner you know how important customer service is so take that with a grain of salt also
  11. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    Nope I'm just a specifying and design engineer
  12. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    Then you should have a look at any other tankless system. Navain is nothing but trouble, there is tons of forums with tons of consumer complaints about their units.
  13. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    SewerRatz,

    Google "Rannai problem, Bosch problem, Noritz problem"

    You will get as many or more complaints about them.

    It appears all tend to be plagued by application and install problems.
  14. Dovels INC.

    Dovels INC. New Member

    Messages:
    7
    well im just an installer that knows nothing compared to a big eng. like you but the problem is with your tech suport so why dont you put your mind to that problem and tell me how you will fix that. also how can it be a install problem when all you do is hang it on the wall hook up 2 water lines and a gas line plug it in and install a 3 in pvc flue. looks to me that it is over engineered
  15. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    I did that. I did not find very many complaints about Noritz at all, Bosch I found tons along with Rheem, and Rinnai has has as many as Navain. Navain is still junk. They brag about having a unit with a built in buffer tank. I fell for this till I found out they did it to help with the massive temperature fluctuations these units have and still have with their little built in buffer tanks.
  16. flamefix

    flamefix New Member

    Messages:
    71
    Location:
    Exeter, England
    Can someone confirm to me what you mean by Tankless heaters?

    I am assuming you mean instantaneous water heaters.

    I fit these all the time, and it is mandatory to fit Condensing water heaters in this country. Often the instantaneous water heaters are central heating boiler combined. We call these boilers combi's for short. Typically they are very efficient.

    However, they can only heat so much water by a fixed maximum amount of temperature rise so flow rates will be determined by the cold water main supply and the temperature of the cold water supply. At max demand they pull a lot of gas therefore gas supply pipes need to be adequately sized.

    A majority of modern homes in the UK are fitted with a form of instantaneous heating systems. Working with solar as I do and ditting the systems I have I would say if there is only a couple in a small household then Combi is suitable. But large hot water demand storage is better and less gas would be used in a well designed system in my opinion.

    A 30kW combi boiler will provide 14 litres/min at 30°C, 12.5 litres/min at 35°C, and 7 litres/min at 55°C rise.

    Therefore to get 14 litres at 50c you would need the incoming water to be at 20c.

    There is no problem with using these boilers they are generally reliable and having only briefly read through this post the talk about fumes etc seems a bit exaggerated.

    Perhaps you might like to read through this article?

    http://plumbing-help.net/Introduction to Combination Boilers.html
  17. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    Sorry to hear about your Navien woes, my experience has been that they are usually attributed to insufficient gas and changing water pressures. Its no secret that the 98% is achieved by not using a bypass valve in the unit and thus not flashing the water. Which certainly helps in harder water applications.

    Having used the Navien, the buffer tank was needed for the mass required to maintain temp for no delay. You see if it was for temp swings it would have been on the outlet, not the inlet water as it is.

    Regarding the rest, while I don't care for all the Paloma's, Rheem and Ruud included, I do like the Takagi, Rinnai, and Noritz. In fact my first tankless over 20 years ago was the CEC (later Bosch) Aquastar 170. While not the most efficient it was endless hot water and before Takagi introduced the water bypass valve to the rest, a thermostatic mixing valve made the old Aquastar work quite well. After about 14 years I replaced it with a Rinnai, even though it still worked.

    There is no denying that Noritz makes a quality unit, but perhaps being #4 or 5 in the shippment ranks in the US puts their problems with less exposure. Having visited many tankless install jobsites of all brands, perhaps 5% were actual unit problems and the rest install, application, misunderstanding or abuse.

    I believe that the day plumbers carry and use a quality manometer to check change and adjust the tankless units the majority of issues for all will go away.
    Last edited: Sep 5, 2009
  18. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    What are you rambling about Dovels?

    Your procedure for installing a tankless is scary I must say.

    Do/can you read the manual?
  19. heetmiser

    heetmiser New Member

    Messages:
    2
    Location:
    NY
    And now for my quick rant.
    It gets old hearing a navien guy tell us how great his product is, I get it at the wholesaler, from the rep, and from the factory. bottom line is, something in the unit isnt right. first it was the flow sensors, then the board (by the way what generation software are we on now, and how many upgrades is that) now we have plastic elbows failing in the unit (factory recomends stocking a few of these on the truck now,) and meanwhile our customers are getting pretty pissed off.
    I did NOT have any (take that back 1) problems with the last brand we installed,(over 100 units) so I dont think its me.
  20. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    Welcome to your first post heetmiser (the original is in Colorado)

    "I did NOT have any (take that back 1) problems with the last brand we installed,(over 100 units) so I dont think its me."

    Curious, why did you stop installing your last brand and what are you using now and why?
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