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Thread: Thoughts On Navien Vs AO Smith Small Tankless Propane Boiler

  1. #1
    DIY Junior Member CORVAIRWILD's Avatar
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    Default Thoughts On Navien Vs AO Smith Small Tankless Propane Boiler

    I'm building an office for my wife from our 3 car garage. 10'x20'. 4" concrete w embedded PEX over 2" styro over existing concrete. I am super-insulating the walls with double off-set studs so the fiberglass insulation overlaps, and adding a foot of fiberglass to the ceiling.

    The local plumbing supply carries A O Smith and Navien. A O Smith made in USA, my price $933. Navien is made in Japan $1160.

    Both exit thru the wall and will be mounted directly above my wife's desk. She works from home, so noise is important, and less is better. thoughts?
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    DIY Senior Member Reach4's Avatar
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    AO Smith has a "15 year" but it is 12 years on the heat exchanger and and 5 years on warranty, but I don't know what the restrictions are. They give no warranty if you install it yourself.

    http://www.navienamerica.com/WarrantyInformation/ http://www.navienamerica.com/WarrantyInformation/NPE/ seems to exclude damage due to build up, but I don't see a specific hardness cuttoff. One exclusion reads
    Any damage caused by local adverse conditions including but not limited to hard water deposits, lime or mineral build-up, operating in corrosive atmospheric elements.
    They specifically say no warranty for any unit bought via the internet.

    For A O Smith the hardness limit number is 7 grains.
    Water hardness levels must not exceed 7 grains per gallon (120 ppm) for
    single family domestic applications or more than 4 grains per gallon (70 ppm) for all other types of applications.
    So don't assume you get a warranty just because they advertize a warranty. Don't assume that I found all of the weasel words for you.

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    DIY Senior Member zl700's Avatar
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    First
    The AO Smith is a Takagi made in Japan and labeled AO Smith
    The Navien is made in S Korea

    Second
    Don't use a tankless water heater as a boiler for your radiant heat, you will be sorry in so many ways, too many to list here.

    Third
    It's an office why wouldn't you put the utilities in a mechanical closet to hide all the pipes, pump and wiring? All that would like like crap over a desk
    Last edited by zl700; 03-12-2014 at 08:10 PM.
    If Payback is so important to you, why are you not driving a Toyota Corolla?

  4. #4
    DIY Junior Member CORVAIRWILD's Avatar
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    That's why I came here for advice. What should I use to heat the floor? I thot the tankless was THE way to heat in floor?!?!?

    There's only 9' exterior walls and I'd like to vent directly outside, in the back away from the street side. I could mount it on a side wall and runs along the shared garage wall, or I guess I could run the system on the street side...

    And the ceiling is 10', so if I mount the heater on the wall above the desk it's not to unsightly, and mount the expansion tank higher up, and use white pipes... I could build a small chase for the pipes

    Is there a thread here I should look at?

    And sorry to confuse the origins of the units, my bad

  5. #5
    DIY Senior Member houptee's Avatar
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    What model AO smith are they quoting you that price?

    A Takagi TK Jr2 is worth a google search.

    If you plan to install it yourself they sell Navien, Rinnai, and Takagi so you could print it out and negotiate price with local supplier.
    Last edited by Terry; 03-14-2014 at 09:51 AM.

  6. #6
    DIY Junior Member CORVAIRWILD's Avatar
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    Here's a link to the recommended unit...

    http://www.pricegrabber.com/outdoors...compare_prices

    why is it 1/2 what my salesman is quoting???

    Are the units that much different?

  7. #7
    DIY Senior Member houptee's Avatar
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    Takagi and AO Smith formed a marketing partnership a few years ago.
    Like zl700 said the AO is a Takagi with different label on it.

    As far as price who knows guess he is quoting your full list price and does he actually stock it or does he order it and it comes via ups to his supply house?
    If so his inventory carrying cost is nothing, but he does have a brick and mortar storefront and the expenses to keep the place open.

    Its hard to try and support local businesses when the price is so far away from online prices but nobody pays me whatever i quote they shop around get 3 quotes and then still try to get you to throw in extra stuff or offer less its just business.

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    DIY Junior Member CORVAIRWILD's Avatar
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    Here's the quote. I dunno if they have it in stock, locally or at main store or drop ship.

    So what do you recommend I use?
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    Last edited by CORVAIRWILD; 03-13-2014 at 07:51 PM.

  9. #9
    DIY Senior Member houptee's Avatar
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    That AO model is equivalent to the Takagi T-H3J-DV/IN
    http://takagi.com/index.php?product_id=139&page_id=2

    His price is good its actually lower than what I find online for that model Takagi

    Question is do you only want to heat that 10x20 floor with it? Did you do any type of heat load calculation to size the required boiler/water heater?
    If so you might not really need to spend the extra money on a "condensing" water heater for that small of a load.
    The TK jr2 is not condensing that's why it is half the price of the quoted models but has 140k btu max capacity.
    It does require special cat 3 stainless venting you cannot use PVC to vent a TK jr.
    http://takagi.com/index.php?product_id=101&page_id=2

  10. #10
    DIY Junior Member CORVAIRWILD's Avatar
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    No, I didn't do a load check, but a really well insulated 9x20 w 10 foot ceiling can't take much to heat. And this is just to heat this space, the rest of the house already has oil HW heat, but there's a concrete floored 10' breezeway in between.

    So no condensing? and how much is the SS stack compared to PVC? Does it require the same 12" clearance to a window? We're downsizing the window to accommodate that
    Last edited by CORVAIRWILD; 03-13-2014 at 09:44 PM.

  11. #11
    DIY Senior Member houptee's Avatar
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    If you go out the top of unit with an adapter then elbow thru wall with a wall thimble then have a vent hood on outside you need total of 4 vent parts.
    The Z-Vent brand is less than the takagi branded venting parts and they add up to $158 in stainless from a site in Fla discounttankless.net or google designer plumbing

    The clearance from any type of building openings is less distance if the unit is "direct vent" meaning it has a second intake air pipe for combustion air vs. using air from the room.
    The direct vent conversion kit for takagi tkjr is $58 extra if you think you need it.

    So total would be around $786 from that website for Tkjr unit and venting, free ship, no sales tax.

    Your unit is 933 plus tax
    Last edited by houptee; 03-13-2014 at 10:17 PM.

  12. #12
    DIY Junior Member CORVAIRWILD's Avatar
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    So why not the condensing? My application too small? And what outside/window clearance do I need? The shiny colorful brochure doesn't list any numbers.

    I'll go look at the link

  13. #13
    DIY Senior Member houptee's Avatar
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    You have to download the full manual pdf from takagi link and read the section on venting, it shows diagrams of various window and soffit clearances etc but these are dictated by the local codes not the manufacturer of the equipment. In NJ we use the National Fuel Gas Code but NY might use something else.

    Im not saying the TKjr is better than the other units you were quoted, just making a suggestion for alternative unit since you have a fairly small slab, the bigger units you mentioned might be overkill on the btus since radiant is run at lower temps.

    If a condensing unit will save you a measurable amount of energy I do not know for sure, only that the cost difference is much higher, and you probably need a condensate drain pump etc so more parts and piping.

  14. #14
    DIY Senior Member houptee's Avatar
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    Well first off there are "tankless water heaters" that can be used for space heating, like the models you have looked at, but they are not classified "boilers" so have no AFUE energy ratings, only the EF rating used to test domestic water heating.

    There are "wall hung boilers" that are made for space heating and have AFUE energy ratings like a regular boiler.

    Then in both categories there are condensing and non condensing models.

    So its hard to compare a water heater to a boiler based on the energy ratings because they are not the same tests.

    So keep googling around and see what other radiant floor systems installers have used and had good results with in your climate.

  15. #15
    DIY Junior Member CORVAIRWILD's Avatar
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    Jeez... all true...

    But back OT... I was at another plumbing supplier, and the clerk suggested an electric boiler. Since I only have less than 200sq and 10' ceiling... I wonder if the solar cells I plan to power the house/office with will be able to handle the 25 amps the elec boiler requires? I have a meeting w the solar installer tmrw. I'll be sure to ask. Electric would require only a 10g cable-25 amps, no gas-bottle-chimney. Worth asking!

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