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Tankless Water heater?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by NCFord, Mar 24, 2013.

  1. NCFord

    NCFord Member

    Joined:
    Jun 5, 2011
    Messages:
    148
    Loc:
    central NC
    I have a tankless hot water heater and was wondering how to most folks are heating their water with their boiler? I could install a hot water tank and heat it in the winter with a sidearm exchanger and just turn of fthe thankless. I also thought of installing a plate heat exchanger prior to the tankless, but I don't know exactly how the tankless works. I think it works on flow not temp? Any suggestions would help, as I am planning my system. Thanks!

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  2. BoilerMan

    BoilerMan Minister of Fire

    Joined:
    Apr 16, 2012
    Messages:
    1,519
    Loc:
    Northern Maine
    I think it's best to have two seperate systems. A gas fired tankless is great, but is hard to integrate with other types of heating systems. They do not like pre-heated water, and are not boilers so useing them with an indirect is out as well. I'd use the tankless in the summer, and see if you can find a big indirect or a 40+ gallong electric and heat it via-plate exchanger with your wood boiler.
    Electric tankless are very easy to integrate though as they can be used as booster heaters.


    TS
  3. woodsmaster

    woodsmaster Minister of Fire

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    Jan 25, 2010
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    2,425
    Loc:
    N.W. Ohio
    How much hot water do you use ? I have a side arm on a 80 gallon tank with no circ. on the domestic side. With a family of five I need 150 deg plus water for it to keep up if we are having a high demand period, baths, dishes laundry all close together. I try to schedule my burn for the peak demand and don't have any problems running out hot water. I think if there was a circ. on the domestic side it would recover faster, but Ideally I'd like to have a flat plate on demand setup to eliminate some of the mixing in storage. I'd oversize it a little to take advantage of the storage since I have low temp emitters.
  4. NCFord

    NCFord Member

    Joined:
    Jun 5, 2011
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    148
    Loc:
    central NC
    Thanks, a storage tank works for me... easy and not very much $!
  5. NCFord

    NCFord Member

    Joined:
    Jun 5, 2011
    Messages:
    148
    Loc:
    central NC
    Does anyone use just a plate exchanger for hot water? I was thinking if I just unplug my gas tankless during the heating season and install a plate exchanger. I don't know if I could get enough hot water on the domestic side though. any thoughts?
  6. heaterman

    heaterman Minister of Fire

    Joined:
    Oct 16, 2007
    Messages:
    2,980
    Loc:
    Falmouth, Michigan
    Preheating the water going into the tankless will not work for crap. They operate on not only flow but also temp differential. If your incoming water was at say 100* the tankless would never fire at full capacity if it fired at all.

    We always use a storage tank, size would be your choice, and pump both sides of a plate type HX. If you have a good steady supply of 170-180* water from the wood boiler you can make about all the water you could normally use with a 5x12-10 plate HX.

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