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  1. #1
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    Default Tankless Water Heater For Floor Heat

    Anybody care to share information about using the new style tankless water heaters for floor heat? I need to replace my old Jarco 350K btu money pit with something new and more energy efficient.

    I’ve been doing some extensive research and comparing different demand heaters, Takagi, Paloma, Rinnai to name a few. Some are condensing units and some non-condensing. The non-condensing are usually about 84-85% efficient and the condensing units are 94-98% efficient. The condensing units can be vented using PVC while the less efficient units need to be vented using stainless steel vent pipe with a condensation drain added to the vent stack which is more costly.

    Some of the heat exchangers are copper and some are Stainless steel and copper. The condensing units usually use stainless and copper.

    The problem I’m having is trying to determine what will work and how well it will hold up running Polyethylene Glycol in the system. Most of these demand heaters are manufactured for heating “Water” and don’t offer details or suggestions when using them in hydronics or snow melt systems which is basically what we have.

    I have my eye on this model after doing some research…It’s the Paloma PHH-32RDV. It’s a condensing boiler with a 94% efficiency rating. It has a copper/Stainless steel heat exchanger, 199,999 btu rating, can be vented using PVC, has a direct vent cold air intake, and can heat water +35° at 9.5 GPM and 77° at 4.9 GPM Temperature rise.

    What are the pro’s and con’s of using a heater/boiler like this? This one is realitively inexpensive compared to “Boilers” on the market. The one I mention can be bought for less than $1300 which is considerably cheaper than the Takagi TM32 commercial that only uses a copper heat exchanger and has to be vented using Stainless Steel Pipe. I know some of you are using these demand heaters for floor heat. So tell us what model your using, why, and how well its working for you. Thanks!

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    Bubbles Galore (10-10-2012)

  3. #2
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    Default

    This website should be a great help. It shows plumbing of radiant floor heat using a on demand heater:

    http://www.radiantcompany.com/heatso...hematics.shtml
    www.carwashbusiness101.com "Newbies Start Here"

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    Bubbles Galore (10-10-2012)

  5. #3
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    Default

    Those are nice diagrams. I just bought a Lochinvar 199K 96%
    eff. boiler from carwashboilers.com Not sure if this makes a difference,
    but every 2 years we have the boiler inspector stop by. $35 to the state,
    and the inspector is sent by my insurance co. They test the low water
    cutoff, and the overpressure valve. I know the palomas shut off when
    out of water, but not sure if it would meet our states specs, like the
    other boilers. I bought the boiler for $4200, and found a hvac guy to
    do the complete install in a couple weeks- plumbing, gas, and electrical
    changes plus drill a 4in hole thru concrete for the single intake and
    exhaust. Just 4 to 5 hours at their rate plus materials they figured.
    Am I missing the obviously cheaper way to go. Why should i spend
    more for about the same?

    http://www.carwashboilers.com/knight...y-boilers.html

  6. #4
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    Post Something to consider

    Most people are not aware that more glycol causes a loss of heat transfer with the same input BTU expenditure. I myself was surprised when I first saw a mechanical engineering trade journal article showing the proof etc. a few years ago.

    Something to consider ... especially the potentially more harsh winter areas & the more dense the glycol needs to be.

    At our place we have just boiler water in the main boiler setup. That way at the point of combustion it is more efficient. From there we use Spirec heat exchangers to circulate the boiler water on one "in & out" of the Stainless Exchanger & the glycol on the other "in & out". I did get help from a mechanical engineer back in about 1991 or so for the original setup on the design. We don't regret having gone with that approach. Here is a link to the Spirec website.

    http://www.spirec.com

    mike

  7. #5
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    Default

    The more I research this the more issues I'm finding that needs to be overcome. The glycol being one of them. It consumes about 10% of the total BTU output. Another issue I see with the Demand Style Wall heaters is the amount of Head Pressure you need to overcome in the unit itself to produce the rated flow. Let alone the head pressure in the zones. The Takagi T-H2-DV-NG 199K BTU Condensing boiler adds 110 feet of head pressure in the unit itself at the rated 9 gpm flow rate. It would take more than a Taco Stye pump to produce the PSI to obtain the rated flow.

    This is not going to be as easy as I had thought. Theres a lot more to it than putting a Taco pump between the boiler and manifolds. There are diagrams out there that shows it can be done. I'm not giving up yet...

    Thanks for the Input so far.

  8. #6
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    Default

    Quote Originally Posted by Buzzie8 View Post
    This website should be a great help. It shows plumbing of radiant floor heat using a on demand heater:

    http://www.radiantcompany.com/heatso...hematics.shtml
    Thanks for the link! Although I already found it and studied it hard! In the list of Schematics/Photos, the one labeled "A 2-zone CLOSED system" comes closest to what I need to put together. I believe this is called a Primary and Secondary loop system. This way one pump takes care of the boiler and one pump (or however many you want) takes care of the zones. I need to call Takagi and see what size pump is required just for the boiler.

    I found (2) pulications online for snow melt systems that might be of use. I uploaded them to my server for download. There is some good information about how to size a system for snow melt. Basically what we're trying to accomplish.

    http://bcoweb.com/photos/Viega_Snow_Melting_System.pdf

    http://bcoweb.com/photos/CPS_Snowmelt.ppt

    Addining another useful link...

    http://www.radiantcompany.com/manual/index.shtml
    Last edited by 2Biz; 10-12-2012 at 03:04 AM.

  9. #7
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    Default

    You will need a multistage pump
    Vice President of everything & the Janitor


  10. #8
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    Default

    I called Tech support at Takagi and he said a Taco 009 SS pump is what they recommend to supply water/glycol to the boiler. 10 gpm and 35 feet of head pressure. This is just for the boiler. You need another pump for the loops.

    This diagram (Attached) is about as simple as you can get. It is all you need for Snow Melt and when using a Condensing-Modulating Boiler.

    http://bcoweb.com/photos/piping schematic.pdf

  11. #9
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    Post

    Quote Originally Posted by 2Biz View Post
    I called Tech support at Takagi and he said a Taco 009 SS pump is what they recommend to supply water/glycol to the boiler. 10 gpm and 35 feet of head pressure. This is just for the boiler. You need another pump for the loops.

    This diagram (Attached) is about as simple as you can get. It is all you need for Snow Melt and when using a Condensing-Modulating Boiler.

    http://bcoweb.com/photos/piping schematic.pdf
    2Biz,

    I wonder if the following unit's own built in circulator would mean the unit's circulation would be taken care of ... eliminationg the need to buy a Taco 009 pump?

    http://www.globalindustrial.com/p/pl...ni-buffer-tank

    mike

  12. #10
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    Default

    Looks like a nice unit and comaparable to the Takagi T-H2-DV-ng or the new style T-H3-DV...The Takagi has slightly higher ratings...6.1 GPM @ 60° temp rise and 5 GPM @ 75° temp rise compared to the Navien's 5.8 GPM @ 50° temp rise. It does have a nice feature, dual SS heat exchangers. The Takagi only has a Primary SS heat exchanger and copper secondary.

    I downloaded the Navien's manual and it didn't have anything listed on the pump specs. So I can't help you with that. But you might want to take a look at the diagram in this brochure on the plumbing hookups. It has a hot outlet and hot return along with a cold water inlet. Different than the Takagi which only has a cold intake and hot outlet. Here is the link to the brochure:

    http://www.navienamerica.com/PDS/ftp...RNP_120823.pdf


    I don't know how you would plumb this model with the internal pump and having the "Hot" circulation loop with the single cold inlet....I would call Tech Support to see how that works.

 

 
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