Navien Tankless Water Heater Comments and questions

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

  1. techsavy

    techsavy New Member

    Messages:
    15
    Location:
    ontario

    This is actually not the way to go about this. Your tankless is not a boiler and therefore cannot be used in the manner described. Your tankless must heat domestic water directly. You can add a heat exchanger to heat the space indirectly, but keep in mind that there are rules guiding how much space heating can be done using a water heater. see the following link http://www.noritz.com/u/plumbing_diagrams/nr83/7a1_nr83_dhw_rad.pdf
  2. MEE

    MEE New Member

    Messages:
    1
    Location:
    denver co.
    in the spring i helped remove an old corroded boiler from a house with about 12 bedrooms and 4 bathrooms. the boiler and 2 water heaters supplied DHW and radiant heat. we
    replaced it with a Takagi tankless to run the DHW for the summer months with the intentions of plumbing it for radiant heat before winter. Well, the home owner found a Navien
    CH240 to do the job instead. I have to say that i liked the Takagi. It installed easy and did provide almost instant hot water, and was simple to operate. We are however
    experiencing problems with the Navien. It keeps giving us error codes for low pressure just running one sink for less than 2 minutes, and we can't adjust for elevation with a dip
    switch like the Takagi. I have read about 2 years worth of posts on this subject and frankly i have some mixed emotions on the whole tankless concept. Anyone have any
    suggestions?
  3. Dana

    Dana In the trades

    Messages:
    2,814
    Location:
    01609
    Tankless Adviser: Firing rate is only a secondary factor on the raw combustion efficiency, and setpoint temp is third-order factor for tankless units. Incoming water temp is primary, and it's ALWAYS going to be well into the condensing range in DHW mode, but can be much warmer/less efficient in space heating applications with high return-water temps.

    In DHW mode whether it's at min-mod or full-fire a condensing tankless will always be north of 95% steady-state, whether the output temp is set to 40C or if it's set to 60C. There will always be condensing going on in part of the heat exchanger that contains water under 50C. But flue purges on short-draws eat into efficiency considerably, since every purge extracts the same amount of heat out of the the heat exchanger whether you just took a 20 minute shower, or whether you just rinsed your hands. On the former that loss is a negligible fraction, on the latter it's a good chunk of the total burn. The US DOE EF test over-rates tankless units relative to tanks, since the use profile is all long draws.

    I'm curious about the test data on the mini-buffered Naviens- is that Centre for Energy and the Environment available online?
  4. techsavy

    techsavy New Member

    Messages:
    15
    Location:
    ontario

    Set-point can play a very important role based on the design of a tankless water heater. Some tankless water heater manufacturers are known to use bypass valves (controlled or fixed) to assist with heat exchanger protection and temperature stability. If the bypass is controlled, setpoint will determine if the bypass is partially opened, fully open, or fully closed. If bypass remains fully closed, then set-point as you say becomes less relevant.

    - Agree on efficiency drops on space heating mode due to high return water temperature being too close to or depending on application above dew point.
    -Problem with the Navien tankless water heating units with buffer tanks is that the bufffer tank's recirculation pump when activated mixes heated water with cold water and increases inlet water temperature. I have not looked at the pump curve in the units, but since tankless water heater manufacturers typically require 2 GPM flow through the heat exchanger in recirculation mode, I can't imagine that they would recirculate the buffer tank with anything less. Here again, the set-point will affect the efficiency of the unit as the higher the setpoint, the higher the temperature at which water in the buffer tank will be recirculated into incoming cold water line and hence into the water heater. If Navien used Takagi as a reference point, then the buffer tank will always be recirculated on hot water demand, and as such, the inlet water temperature will always be greater than the city supply. I can not confirm this, as I have not done any tests on Navien units, but I am very familiar with Takagi.
    - A problem with the Navien CH combi boilers, is that it is a boiler first and a water heater second. This means that it essentially operates as a boiler and hence the domestic hot water does not flow through the heat exchanger. As a result, even in domestic hot water mode, the system will be hard pressed to condense. This is partially why the Navien combi-boiler has lost its energy star rating (visit Navien's website to find out more about their energy star rating for combi boilers). Here again, setpoint will be a factor, as the return water temperature on the boiler side will be influenced based on closest approach temperature of the flat plate heat exchanger employed for domestic hot water production.
  5. techsavy

    techsavy New Member

    Messages:
    15
    Location:
    ontario

    If you followed the installation diagrams published in the Navian product installation manual, then you could be up for some challenges right off the back. Notice that the pump on the Navien CH combi-boiler is on the boiler loop outlet inside the unit. Notice also that they recommend placement of the expansion tank at the boiler outlet, which means that the pump will theoretically not be able to increase pressure above static pressure. While this is only one problem with the diagrams, there are more, so I suggest getting your hands on a proper diagram and use that as your guide.
  6. Dana

    Dana In the trades

    Messages:
    2,814
    Location:
    01609
    Bypass open or closed, the setpoint doesn't affect the steady-state (or as-used, intermittent) efficiency of the unit (even though it may be important for temperature stability.)

    The mini-buffered units only suffer a standby loss during their programmed time-of-day active periods, and the hit from lower combustion efficiency for heating that liter or two of water is probably less of an issue than the flue purge losses during buffer-temp-maintenance-only burns (the flue purge loss on very short draws will still dominate the loss figure in most use profiles.) On longer draws the combustion efficiency is still determined primrialy by the incoming water temp, and it's barely affected by the setpoint of the mini-tankL: Mixing the recirculation tank-let with incoming water still yields a temp entering the HX is deep into the condensing zone after the first liter of draw, even if you have it set to 60C. The steep part of the condensing curve in a natural gas burner typically starts at ~87% @ ~52C, and you're already at 95% or more with 40-45C incoming water, climbing only slowly to 98% as it falls to 30C & lower. With 10-15C water in from the street it it dilutes that 50-60C water well into the condensing zone quickly.

    I've been mostly un-impressed with the design of either the Rinnai or the Navien CH combis. I'm not surprised that the Navien fails to condense much under DHW-only loads (but then again, neither do most mod-con + indirect systems as-operated, since they tend to set the indirect tank temp too high.)

    I'd still like to read the Centre for Energy and the Environment piece though, if it's available online. (If not available on the web, ping me via PM message.)
    Last edited by a moderator: Nov 5, 2012
  7. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    "This is partially why the Navien combi-boiler has lost its energy star rating (visit Navien's website to find out more about their energy star rating for combi boilers"

    Anothe misleadingng untruth from you sir, Mr Tankless Adviser

    Since there is no combi listing on DOE / Energy Star, Navien listed their combi as a water heater.
    With recent DOE tightening and failure to create a a combi boiler classification, combis such as the Prestige, Challenger and a few others were moved over to boiler classificarequiringreing ASME and CSA 4.9 testing to name some.
    Check the boiler listing where it is Energy Star listed.

    Centre for Energy and the Environment is online and appears to be written to favor tanks.
    http://mncee.org/Innovation-Exchange/Resources/Actual-Savings-and-Performance-of-Natural-Gas-Tank/

    "If you followed the installation diagrams published in the Navian product installation manual, then you could be up for some challenges right off the back. Notice that the pump on the Navien CH combi-boiler is on the boiler loop outlet inside the unit. Notice also that they recommend placement of the expansion tank at the boiler outlet, which means that the pump will theoretically not be able to increase pressure above static pressure. While this is only one problem with the diagrams, there are more, so I suggest getting your hands on a proper diagram and use that as your guide."

    You fail to understand the purpose of a boiler pump which in most cases is not the system pump, look at other combi units with internal circulator.

    MEE if your getting low pressure codes on a CH you either didnt hook up the automated feeder to water connection, or installed a PRV which wont let it get to fill shutoff, pressure switch is downstream of outlet of internal circ. Factory setting is 17 PSI, circ creates 6 so its static 11 + 6 = 17 for fill shut off (Circ always runs when feeding water, for auto purging) this setting is adjustable from 12 to 30 PSI on remote.
    Last edited by a moderator: Nov 5, 2012
  8. Dana

    Dana In the trades

    Messages:
    2,814
    Location:
    01609
    That document is consistent with (and references) laboratory work done over the past decade by the Davis Group in CA, so I'm not too surprised.

    Favor tanks? Not really- more like favoring the facts (as meticulously measured in-situ rather than presumed in a laboratory or rating agency test protocol.) Tankless units definitely save fuel, but the benefits are far less than implied by the DOE EF test numbers or steady-state performance numbers.

    Efficiency is rarely the primary reason people give for going tankless in the first place. Not running out of HW is #1 most-cited, space savings is #2.

    The standby power is substantial on some of them, which makes me think the zero-electricity cheapo Bosch 1600H would be a better choice in some applications. (It'll support one shower flow at a time in a northern Maine winter, but not much more.)
  9. Willowtree

    Willowtree New Member

    Messages:
    1
    Location:
    Upstate NY- United States
    Just the facts men. I purchased a Homemaster instantaneous hot water heater in 1979 as a DHW backup for my evacuated tube solar collectors. It was on a closed loop w/ treated dionized water. I never flushed the system. I removed it when I sold my house in 2005. That's 25+ years! It was working fine and I gave both the solar system and the instantaneous hot water heater to a friend who currently is using it. Sounds remarkable but it is a fact. I currently have Navien double units paralleled to provide DHW water for a six unit apartment house. We do experience the thermal lag inherent w/ all instantaneous systems but the tenants have been understanding and no complaints. These units are more sophisticated so I do expect potential problems. Finding a trusted and supportive installer is key. I must say that a few of the forum contributors would not be on my list of repairman. The systems do require more knowledgeable technicians. If you like the easy/simple and less efficient life then stick w/ tanks. This applies to both installers and home owners. There is plenty of business out there for all of us.
  10. Surfing Plumber

    Surfing Plumber New Member

    Messages:
    10
    Location:
    Orange County, CA
    I have installed Naviens before and let me tell you, there are A LOT of problems with these heaters. Which is fine because I know not everything is perfect. But to find the support and parts from Navien is almost impossible. They will give you the run around and takes a lot of convincing to get the part(s) needed to fix the heater for customers. I am sick of dealing with them.

    I now install Noritz, their technicians are great, warranty is awesome (even with controlled recirc system). I highly recommend going with Noritz, their new condensing PVC line up is great! 3" PVC and up to 60+ feet in vent length!!!!
  11. xmdxtremek

    xmdxtremek New Member

    Messages:
    1
    Location:
    New York
    Hey guys we just recently moved into a newly renovated apartment. And it has a Navien NR180 unit. When the hot water is on it makes the most rediculous loud vibrations and grumbles you can hear it upstairs and all over the apartment and the damn thing is in my room when I am sleeping my roomies use hot water it is like hell. Is this normal for a unit to make loud grumbles? and this is not the the same engine noise that you hear spinning that is ok I can bear the engine cycle noise but this loud vibration noise is out of hand. Please tell me its not normal and can be fixed?
  12. ImpliedConsent

    ImpliedConsent New Member

    Messages:
    17
    Location:
    GA United States
    Update from over the pond. We're well into our 2nd year of NR-210A ownership. I did an annual flush of the system before I deployed (NOV '11). My wife asked me about the servicing recently and said that she wanted to learn in case ... well ... you know. Since I clearly marked incoming/hot water, bought/cut the service lines/bucket, it was all there. I just pointed her to a YouTube video and she nailed it first time. I think she'll be OK. So far, we haven't had to call anyone concerning our hot water needs. I feel pretty comfortable with our experience. As I go back to wonder why my experience is different from others, I believe that it's still the quality of the installation, it's certainly not a DIY job. TY'all for my learning experience.
  13. jimdarcy

    jimdarcy New Member

    Messages:
    3
    Location:
    IL
    Eternal advice

    Hi all, new user here, great forum. I am preparing to replace my 2, 18 year old 50G water heaters. I am on well water, one installer has recommended the Eternal Hybrid GU195, he says the stainless guts will hold up much better than copper. I currently have the traditional venting, access to uninterruptable power and an interior liquids drain. The question is...is Eternal with the premium price, and now it looks like the tax rebate is gone(not 100% sure on that). any thoughts or comments are appreciated.
    Thanks
    Jim
  14. QueBall

    QueBall New Member

    Messages:
    5
    Location:
    Edmonton, AB
    I know. Responding to a 2008 thread.

    Anyhow, Navien NR-210a installed here about 2 years ago. Been a pretty good experience I must say.

    No, it's not maintenance free. You should flush / descale the unit on a regular basis. Frequency will depend on your local water quality. I probably only need to do it once a year here, but it's not very hard so I have done it more frequently than that.

    Biggest problem I had was pretty silly. I was getting error code 10 indicating an air pressure sensor fault. The first time that happened I learned there was a screen on the incoming air vent that got plugged up with poplar (tree) fluff during the time of year when you would swear it's snowing outside there is so much of those seeds in the air. So no big deal, it's easy to scrape off. The next time it happened the filter was clean so I just reset the unit and it was fine again for a day. But it kept happening. So I went outside and found that the vent cover had fallen off. Apparently the BH rated vent pipe is a different material than the vent caps so the solvent didn't work to glue them together and the cap fell out of the exhaust vent. Well a mouse had taken the opportunity to start building a nest in a nice warm pipe. The mouse likely took off the first time we fired up the shower but now we had a pipe full of grass. Glad it wasn't the air intake that was missing the vent cap, at least the air flow was pushing the debris out rather than sucking it in. The exhaust pipe has a slope back to the heater so the condensate flows back instead of leaving icicles on the exhaust pipe so it was difficult to pull all the grass up and out, I'm sure there is a little bit left I couldn't reach with hooking up as many extensions to the shop vac pipe I could find.

    So there is an installers note, do not assume the solvent you used for all the vent piping will work on that vent cap.

    The A models have the recirculation pump and a mini buffer tank in them. I currently have mine set for internal recirculation using the mini tank. It's allows the heater to support low flow rates in my case. It doesn't really help with delivering hot water to the taps any faster since it still has to travel from the heater to the tap. I'm hoping to upgrade the piping to add recirculation to our sinks for hand washing. I can wait for the delivery of hot water for showers, but it would be nice to have the instant heat on our sinks for hand washing.

    Installation on this was not easy. I did most of it myself with help from some handy family members. Our old builder grade tank died on us after a long life and we wanted it gone. Energy saving was not the primary goal, we wanted the space back and we wanted the endless hot water feature. There were rebates at the time to bring the cost down but it was certainly more expensive than simply replacing the old tank.
    The obvious first challenge was venting. Difficult, but relatively straight forward. One reason for picking the Navien was so we could use the longer PVC pipes and place the heater on an inside wall. Plumber friend of mine told me to look into it.

    The really hard bit that I was not expecting was upgrading the gas feed. I figured that all we needed to do was reroute the gas from the old heater to the new location but then I found out 1/2" gas line is not sufficient. Plan B was to come off the 3/4" line going to the furnace, BBQ, and garage heater but that was not enough to support all that stuff running on the same line at the same time.
    So plan C. Run a brand new line all the way outside to the meter. What a chore, took me a few days, but it's perfect and with a home run to the meter we have never had a gas flow problem. I have read about many others who have flow or oscillation pressure problems with their gas and we have never once had issues with that. Inspection was impressed we caught this gas demand detail. I made one mistake I have been meaning to fix, I forgot to put a union after the shut off valve. It's only a problem if I need to remove the heater for some reason. It was -29*C the other day, would suck to have to wait for the furnace to turn off to get hot water. (That furnace is likely the next one to need replacing)

    I see the latest model of Navien is designed to handle some of these retrofit challenges which makes for a pretty interesting product. If that was available back then we likely wouldn't have a problem pulling our gas connection off the line to the furnace but now that it's all done I'm glad we were able to do it the right way.

    So what doesn't work as advertised? Well I had hoped the buffer thank would improve the time to get hot water from the tankless system but it doesn't seem to really work that well. It does help with low flow and the Navien seems pretty good at providing a more consistent temperature than another tankless install my parents had. There is still a noticeable delay to get hot water through the system. Going to investigate hooking up the recirculation system and running some return loops from the sinks to try and improve that. It seems like the internal buffer thank isn't large enough to work as I hoped. The vast majority of water volume of the tank ends up in the lines and although the design helps to reduce that water sandwich effect it's not gone as a little bit of warm water comes after a bit of time then it kind of stays luke warm like that until the actual hot water shows up. It does not drop down to really cold water like the unit I tried without a buffer but it doesn't give you the hot water as fast as you want. The internal buffer is an improvement but still not the solution to this complaint.

    The noise is another potential issue. The exhaust fan motor and unit vibrates a bit. I am thinking of putting in some kind of gasket in between the unit and the wall to dampen the vibration. It's in the basement close to our garage entrance and not really any problem, if it were closer to bedrooms or active living spaces I might find it really annoying. If you are looking at these heaters then I suggest a very secure mounting point, and look into what can be done to isolate the vibration. It's not really loud but the vibration kind of reverberates through the wall.

    The maintenance isn't any worse than draining a regular tank would be. Anyone who thought it was maintenance free is nuts. But if you do a good job installing it things work really well.
  15. calabasasplumbing1234

    calabasasplumbing1234 New Member

    Messages:
    2
    Location:
    Calabasas, CA
    I second that. The Navian tankless water heater system has been what I have found to be the best system to recommend. They rarely have any problems, and are built well.
  16. QueBall

    QueBall New Member

    Messages:
    5
    Location:
    Edmonton, AB
    Had a small problem over the weekend with my NR-210A but it was relatively easy to fix.

    There is some kind of air purge valve on the top of the recirculation pump. Mine was leaking and water was dripping out of the threads on the cap (kind of a plastic thumbscrew thing sealing the hole that lets air out of the top of the pump)

    I'm not really sure how this valve is supposed to function as I could find no documentation about it in the Navien service manual. It isn't even listed as a separate replacement part, it's just that black plastic thing that sticks up from the top of the recirculation pump. Would hate to have to buy an entire new pump if this was the only part that needed replacement as it is really easy to remove.

    Once I took mine off I found the threads of the small purge valve were crusty with mineral build up. A quick soak in a vinegar bath and I was able to remove the crust. Put it back on top of the pump and no more leak.

    This happened right after I had shut the water off and drained the tank. When I turned the water back on I had turned it on very slowly at very low pressure. I suspect there was not enough pressure to push against the valve to keep it shut or the part of the valve that floats went a bit askew and did not make a good seal. It seems like it's designed to allow air to pass and then when the full water pressure hits it the pressure is supposed to close the valve but I think I screwed that up by applying low water pressure. (I was doing some other plumbing in the house and one of the old shut off valves on a toilet was leaking so I wanted low pressure in the lines to test with.)

    So whatever that thing is on the top of the recirculation pump may need periodic cleaning when you are doing the regular maintenance / flushing of the tank. Going to add it to my list of things to do. It's a bit of a pain to remove without also removing the motherboard but I have small enough hands I was able to do it without removing anything else. You may have to look at the service manual for removing the recirculation pump to see what connections you can remove to get back there if you don't have freakishly small hands like me.
  17. Cafen8ed

    Cafen8ed New Member

    Messages:
    1
    Location:
    Maryland
    I had a Navien CH-240 installed last Feb. A few weeks ago it stopped making the rumbling noise. I noticed the temp on the thermostat does not reach the 185 as it had in the past. It stays 10-20 degrees lower. If I lower the temp to 160 it still stays 10 degrees lower. (then when the heat comes on , it is coolish air coming hot- we always have hot water)
    When using hot water it drops 60 degrees and does not heat up quickly like it had. Installer told me it was cold outside so water, propane takes time to heat. I called a Navien recommended repair and now they have said the unit is too small to provide service for 3 furnaces and the hot water. Another repairman came out prior, said the flame was not staying constant (there are no error codes) but he was only familiar with the tankless that are used for hot water not dual - furnace & hot water. They are coming back today but hinted that there were other issues with furnace and piping. That did not answer my question about why the unit was noisy and reaching temperatures. They were proposing another type of unit- Pioneer boiler. Any suggestions? Furnaces were installed at the same time- so everything is about 11 months old.
  18. Swedefj40

    Swedefj40 New Member

    Messages:
    1
    Location:
    BC
    Hi, I've been having the E010 error code on my Navien 210 model pretty much since it was installed 5 years ago. Normally I would clean out the air inlet strainer and all would be good. This would happen every 6 months or so so I didn't think nothing of it. However, I am now getting the error every few days now even though the filter is clean. I also noticed that there is a lot of suction as I pull off the front cover of the unit. If I leave the cover off the unit, the error code does not come on nearly as often either. Navien has not responded to my e-mails either. Anyone have any suggestions?
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,949
    Location:
    New England
    It sounds like the air inlet pipe is clogged...you may need to go all the way outside and take a look. The unit should get all of its combustion air from outside, which means there should not be a vacuum in the cabinet.
  20. Terry

    Terry Administrator Staff Member

    Messages:
    14,943
    Location:
    Bothell, Washington
    Navien NPE

    [video=youtube;b2S_7VwkgJc]https://www.youtube.com/watch?v=b2S_7VwkgJc[/video]

    NPE Navien Premium Condensing Tankless Installation Video

    [video=youtube;U7kzE0IzbgA]http://www.youtube.com/watch?v=U7kzE0IzbgA&feature=share&list=UUOkcj5X2Al ZCZ4fgfUhEbCQ[/video]
    Last edited: Apr 28, 2013
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