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A running report

S Ebels
S Ebels Member Posts: 2,322
What type of control setup are you using with the system? Is the Takagi directly connected to the rads or did you pipe it Pri/Sec in order to ensure adequate flow through the water heaterr.


  • Spudwrench
    Spudwrench Member Posts: 47
    A running report (Takagi tankless as boiler)

    Back in '04 I installed a hydronic heating system in my home (Takagi TKjr. tankless as a boiler, Myson panel rads, piped two-pipe direct return in 1" copper.) A few folks on the wall asked for follow up reports on how well it held up.
    The answer: so far, so good. I would like to upgrade to a "real" condensing boiler eventually, but in the meantime, the Takagi has been dead reliable. Heating bills seem about what I would expect for a house of this square footage with leaky windows and no insulation. I sized the radiators for low temp operation and have run the Takagi at 144deg for the past two seasons.
    I understand that a tankless is not a boiler, and wouldn't recommend it for everyone, but it has performed well for me so far. I reserve the right to change my opinion if it craps out in -20deg weather someday and no one will come service it for me!


  • Spudwrench
    Spudwrench Member Posts: 47
    controls for tankless

    I am using a single thermostat controlled circulator. The tankless has an internal flow sensor which fires the burner when it detects more than .75 GPM flow.
    I did not use P/S pumping; my thinking was that the heat exchanger in the Takagi is designed to run at a high delta T (i.e. bringing ground water temp water up to 120deg for domestic hot water.) The Takagi modulates both the burner's BTU and the flow to maintain the electronically programmed output temp (144 deg in my case)...it runs at a huge delta T at start up (due to the Takagi's internal flow control valve), but settles into a 25 to 30 degree delta T after running for a while, so I think my pipe & circ sizing is OK. If I was running multiple zones or TRVs, I think I'd definitely go for a P/S setup, but this is all about simple, low cost hydronic heat. Comfort is actually quite good with this crude setup.

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