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using tankless water heater instead of boiler

DD_5
DD_5 Member Posts: 36
in THE MAIN WALL
Anyone have opinions/experience using a tankless water heater as a heat source for hot water radiant instead of a boiler? How well do they compare? If for example an NG on demand tankless has a NG 19,500 Btu input to 140,000 Btu input does that mean it could handle heating a house with a 120.000 Btu design load? Do they operate too inefficiently over time to make the lower up front cost not worth it? etc...

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Comments

  • Timco
    Timco Member Posts: 3,040
    read other post

    There is a post regarding this in the recent list, maybe page 2? Look at Rinnai's website.



    Tim
    Just a guy running some pipes.
  • Nick_R
    Nick_R Member Posts: 10
    Actually I have

        I installed a system using a Takagi JR as the heat source. I have 1100 sqft of radiant on my first floor, and I also run a hydronic coil in an air handler to heat my second floor. Becuase I am running the hydronic coil I need to operate the Takagi at 182 degrees. I use a mixing valve for the floors. Overall I have had a bunch of issues with the design, but the water heater has functioned as advertised. The install was really easy and it was pretty inexpensive. I can't tell you if the unit will last since I installed it two years ago.

       I learned a lot doing this install myself. If you want to hear about my experience just let me know.   
  • DD_5
    DD_5 Member Posts: 36
    Takagi

    Yeah Nick a Takagi Jr is what I'm thinking of installing. I'm wondering what your flue vent set up is, if its direct vent or not, straight out the wall or vertical through a roof etc. Also what your pump/zone valve distribution is. I'd be adding this on to an existing 3/4" baseboard system. I'll take any info you've got, thanks...

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  • mjcromp
    mjcromp Member Posts: 57
    baseboards??

    I would be weary of baseboards as you'll most likely need a higher temp and get a higher return temp. Most tankless don't like the high return temp and running it at a high temperature might not be the most efficient setup. I have used tankless for many applications radiant and snowmelt but would ask you to seriously consider the application. What is your design temp for the system?

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  • bob eck
    bob eck Member Posts: 930
    Tankless gas water heater as boiler

    Take a look at Noritz tankless gas water heaters and boilers.

    I know if you use a Noritz tankless gas water heater as a boiler the warranty on the heat exchanger goes from 12 years down to 3 years.

    Tankless water heaters are designed to heat cold water for domestic use. Noritz boilers are designed to be a boiler.

    Noritz boilers and tankless gas water heaters vent with their stainless steel vent pipe and their condensing unit vents with PVC pipe.

    Noritz tankless gas water heaters qualify for the 2009 - 2010 Federal Tax Credit of 30% up to $1500.00 if used as a water heater. Noritz boiler does not qualify.

    Also take a look at Triangle Tube 95% AFUE gas wall hung condensing boilers.

    Triangle Tube Prestige Solo and Prestige Excellence gas boilers qualify for the 2009 - 2010 Federal Tax Credit of 30% up to $1500.00
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