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Condensing tankless heater

Hey Rich, I am also looking into the closed system navien heat box coupled with the demand heater for my house. I would really like to get a better idea of what kind of heat load you have and what kind of performance you are seeing. My plan was to use a solar preheat tank and radiant tube in the walkout basement and Myson radiators running at about 140. on the main level and upstairs. Its a relatively modest passive solar house of about 720 sqft per floor. and a heat loss of about 17,000 btu for the upper floors. Any info would be great thanks Kurt

Comments

  • bob w_2
    bob w_2 Member Posts: 4
    Tankless condensing heater

    I'm a newbie to this forum, but have been looking at the posts on the pros and cons of tanlkess vs tank systems.

    I am building a new house, a 1800sqft bungalow. I am making it as efficient as possible. it will have raadiant heat inthe floors. The plumbers gave me options for the DHW:

    A coil in a well insulated tank- Aeroso, if I recall correctly, indirectly heated by the boiler that does the floors.



    A condensing tankless heater by Navien.

    http://www.navienamerica.com/

    With this I could downsize the boiler somewhat. Has anyone had any experience with this? Are their other brands of condensing type heaters? Am I trading one set of problems for another? Between the two types of tankless sytems, I mean.




    Thanks for your help!



    bob
  • kpc_16
    kpc_16 Member Posts: 20
    The choice of...

    water heater should not effect your size of the boiler...unless you have A LOT of hot water needs. Don't add-in domestic hot water sizing into the heatload.I have a small oil boiler 60k w/ a SSU-60. no problems keeping up w/ 3 kids.
    as to the question about the two types...it depends on how good a boiler you have...if that is a 90+ boiler use that w/ an indirect tank. put the extra money into the boiler and indirect that you would spend on a mid afue boiler and tankless wtr, htr....kpc
  • Bruce M_2
    Bruce M_2 Member Posts: 123
    Navien

    The Navien would be a good choice as long as the correct model is installed. You need to know the lowest cold water temperature that you would see in your area in order to determine this. You will have endless hot water and you can shut your heating system in the off season. You did not mention the type heating system and if it is LP or natural gas. Is the radiant heat a boiler or an on demand system?
  • Stars&Stripes
    Stars&Stripes Member Posts: 2
    Korean made

    http://www.alibaba.com/company/10903003.html

    I would stay away from a Korean Made boiler.
  • Bruce M_2
    Bruce M_2 Member Posts: 123
    Korean Quality

    I have found that Korean quality is usually very high. It is not like China. In my own house, I installed a Japanese hot water heater; high quality low fuel usage. Speaking of dependability ratings for automobiles, the 2007 JD Power ratings list Buick and Lexus as number one. While most people are not surprized at the Lexus rating many do not expect Buick to be so highly rated. They have made a dramatic turn around and they sell more Buicks in China than they do in the US.
  • bob w_2
    bob w_2 Member Posts: 4


    Groundwater is pretty cold. Haven't measured it, but it's right there with the brass monkeys...

    We are on NG.

    Using a mod/con boiler for the in floor radiant and a separate FA furnace for HVAC. This was not a great deal more expensive than a fan coil and HRV running off the boiler and offers some redundancy.

    I would therefore have 3 appliances burning NG (4 if you count the BBQ!)
    With the tankless DHW I can effectively shut off the boiler in the (short) summer.
    The question is, is the increased capital cost and maintenance worth it? How much does a good indirect tank cost? ( No one has commented on the Aeroso tank- is there a reason?) Would the boiler cycle too much without the heat load of the floors? Is that an issue?

    As this is an "empty- nester " house, DHW volume will not be as great as when the kids were at home, but will be significantly increased when they come back to visit!

    bob
  • don_185
    don_185 Member Posts: 312
    Save your money

    Save your money and go with the indirect.

    Why add another heatplant that does the same thing the boiler will do.Acourse I'm assuming you have a condnesing boiler.If not..you should have.
  • Stars&Stripes
    Stars&Stripes Member Posts: 2


    Bruce: Wrote
    "I have found that Korean quality is usually very high. It is not like China. In my own house, I installed a Japanese hot water heater; high quality low fuel usage. Speaking of dependability ratings for automobiles, the 2007 JD Power ratings list Buick and Lexus as number one. While most people are not surprized at the Lexus rating many do not expect Buick to be so highly rated. They have made a dramatic turn around and they sell more Buicks in China than they do in the US"


    By giving examples of Quality Japanese and American products have anything to do with a Korean products quality.????????????????
  • Rod Kotiga
    Rod Kotiga Member Posts: 68


    Takagi has one called the TH-1. Two showers at the same time all day even with your cooler water temps. Why store hot water year round when you'll only fire up a flash water heater when your there to use it. 90 plus boilers get 90 plus efficiency when there running nice low temps. Besides when you have failure with the boiler (and one day you will there made by humans) you'll still have hot water. Boiler rooms look there best when everything hangs on the wall. Times they are a changin'.

    Rod
  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562
    Quality

    I have installed several Navien products and have one in my own home. I can assure you that the quality is there along with the technology.

    I have two of there HEATING BOX closed system hydronic units with absolutely no problems. The gentlemen who is the principal of this company was an engineer for Takagi (Japan) before spending 10 years designing the "Heating Box" the condensating tankless has many advantages over the competitors as far as venting options are concerned.

    All the major US water heater companies have a tankless line that they have private labeled from mostly Japanese manufacturers.Some are European.

    Navien has done there homework as far as recirc etc. I would never hesitate using Navien if you are interested in tankless heaters. The principal lives state side and is a very well educated designer/engineer who has worked a manufacturing agreement with Kyong Dong (a huge Korean manufacturer) to make his units.

    I have stated before and will mention again that there is good reason the major tnak manufacturers all have taken on an on demand line. It is inevitable that they will gain more and more market share as the old school reluctance to them changes.

    Not all that long ago boilers were larger due to low efficiency and stack loss. We have learned to lower the volume as we have improved combustion techniques. Time to catch up with the domestic water side of things.

    Over the years I have seen the quality of major domestic water heater manufacturers products shift toward planned obsolescense with heater life cycles engineered around warranties.This along with no current domestic manufacturer of on demand heaters leaves many defensive of the dinosaur storage type heaters.

    Korea has a very good reputation for quality products in many areas. Some of their autos have been bad-mouthed but so was Toyota and Nissan in the 70s and 80s. General Motors is now threatened by Toyota as the dominant overall global leader.

    On demand will be in demand more and more.

    Rich K.
  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562
    Most cost effective

    Ask your contractor about putting the complimentary Navien Heating Box in tandem with the Navien high efficiency on demand water heater. Thid system gives priority to your domestic demand while providing up to 2000 sq. ft of space heating.

    Sounds like you only need hydronics for some infloor, this system would easily do that as you have hot air for the larger portion of your house.This is exactly what I have done in my own home I have about half of the home using infloor with the Navien system.

    This would eliminate the condensing boiler and indirect while adding only the heating box to the on demand.If you e-mail me at the above address I can send you a picture of my system.

    R.Kontny
  • Bruce M_2
    Bruce M_2 Member Posts: 123
    Korean Quality Expanded

    I was giving examples of misconceptions in quality. To make it simple; JD Power ratings for sub compact cars gave the highest award in quality to the KIA Rio. The Koreans are capable of making very high quality products. At one time, Japanese products were considered to be of low quality and now they are considered to be among the highest quality in the world. In looking at quality, perception often lags behind the actual quality of a product.
  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562
    Heat Loss

    Kurt,

    I believe without going into the manual that the heat load could be 80,000 max. Several negatives are the flat plate heat exchangers require pumps to overcome that restriction and are a tad bid noisy (avoid putting the unit under or near your sleeping areas) You can have pressure issues on a well systems if you do not have a constant pressure system. Finally make sure you have enough gas capacity to handle the 200,000 plus btus needed to fire on demand heaters.

    The heating box has two TRVs to adjust separate temperatures for domestic water and space heating. I also have a separate add on TRV to adjust down the temp for my in-floor applications.

    Where do you live I can get you next to a distributor. The rep from Chicago has done quite a few of these systems.
    E-mail if you would like with your variables, right now I am not all that busy.
  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562
    Heat Loss

    Kurt,

    I believe without going into the manual that the heat load could be 80,000 max. Several negatives are the flat plate heat exchangers require pumps to overcome that restriction and are a tad bid noisy (avoid putting the unit under or near your sleeping areas) You can have pressure issues on a well systems if you do not have a constant pressure system. Finally make sure you have enough gas capacity to handle the 200,000 plus btus needed to fire on demand heaters.

    The heating box has two TRVs to adjust separate temperatures for domestic water and space heating. I also have a separate add on TRV to adjust down the temp for my in-floor applications.

    Where do you live I can get you next to a distributor. The rep from Chicago has done quite a few of these systems.
    E-mail if you would like with your variables, right now I am not all that busy.
  • bob eck
    bob eck Member Posts: 928


    Check out Triangle Tube Prestige Excellence 95% AFUE condensing gas boiler with built in 14 gallon stainless steel indirect water heater. Indirect delivers 3GPM 180GPH.
    I also would look at using 1.6 GPM shower head from ALSONS and this indirect could do two showers at one time. If you have room for a 80 gallon tank I would look at using a Well Mate UT80 fiberglass storage tank to take the cold incoming water temp and take it up from 45*F to 55* or 60* this way the boiler and indirect would not use as much energy to deliver your hot domestic water. also the prestige excellence boiler is great for low temp radiant heating jobs and with its outdoor sensor the boiler will only fire at the BTU load required to heat the home and no higher. This is a nice unit.
  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562
    Need to ...

    Address the Legionaire disease issue. Should heat the water to at least 140* if you especially use a tempering tank before the heat source.

    See attached Takagi with Heating Box

    Rich K
  • Rich Kontny_3
    Rich Kontny_3 Member Posts: 562
    A system

  • bob w_2
    bob w_2 Member Posts: 4


    Thanks guys. I've got some work to do...
    If I have my calc's right (the engineers here use kilojoules..) the max heatload in January will be about 120,000 BTU's. Does this sound right ?
    Rich- I can't see your email.Mine is [email protected]
    88uAy8c8Like to see your pictures.

    bob
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    Must say that the Navie sounds quite interesting, but I'd do some serious investigation before using it to drive both a high temperature demand (domestic hot water) and what is [generally] a low temp demand (radiant floors).

    "98% thermal efficiency" as stated in the literature really doesn't tell me much as there are a multitude of ways to "play" with words and numbers. The finest, properly installed condensing/modulating boilers can achieve net (e.g. "final") fuel efficiences at or slightly above this level in ideal circumstances when supplying a space heating system at quite low system temperatures.

    The secondary heat exchanger in the Navie unit--like ANY heat exchanger--will be more efficient the greater the temperature differential between the fluid on both sides of the HX. I can guarantee you that that 98% "thermal efficiency" rating is based on the incoming temperature of domestic (e.g. from your well or public supply) that will be assumed to be significantly lower (think 50F or so) than the return temperature from most space heating systems. I also have a sneaking suspicion that the 98% "thermal efficiency" rating is based on the European method of rating fuels where the energy recoverable via condensation is not considered to be available for use. When heating appliances are rated in this manner--the NET heating value of the fuel as opposed to the GROSS heating value of the fuel--condensing modulating boilers routinely achieve efficiency ABOVE 100%!

    The little buffer tank built into some models is a nice touch if you require recirculation of your domestic hot water, but I seriously doubt you would need that ability in an 1,800 sq.ft. bungalow. Such buffer tank will be truly useless for space heating since it is intended for use only for a well-insulated DHW recirculation system.

    I have little doubt that the Navie could be used for both domestic hot water and space heating in a some situations. My instincts tell me that a properly installed condensing/modulating boiler along the lines of a Muchkin Contender with indirect domestic water tank and the Vision control option would prove to have comparable up-front cost with greater service life.

    Check DEEPLY with that CA distributor of this [almost certainly non-North American] equipment with regards to combining use for DHW and space heating. Buyer beware...
  • bob w_2
    bob w_2 Member Posts: 4
    Navien

    I wasn't planning on using the Navien tankless sytem for radiant heat, only for DHW.
    The question is, do I run an indirect tank from the boiler which will be in place or do I use a tankless system for DHW , leaving the boiler to do the radiant only?

    bob
  • DennisU
    DennisU Member Posts: 6


    > I wasn't planning on using the Navien tankless

    > sytem for radiant heat, only for DHW. The

    > question is, do I run an indirect tank from the

    > boiler which will be in place or do I use a

    > tankless system for DHW , leaving the boiler to

    > do the radiant only?

    >

    > bob



    Both ways will work. The difference will be how efficient the system is....using an indirect will still have thermal losses through the tank and the boiler will have to keep the tank heated at all times.

    If you are looking for the most efficient between the two....go with the Navien.

    If you are looking for the cheapest....go indirect.

    But make sure the btu output of the boiler can handle both your heat load and domestic needs.
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