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Snowmelt w/takagi/glycol questions

fast1200gp Member Posts: 25
Hello all. i recently purchased a house w a glycol filled takagi tk1s fired boiler snowmelt system  .i just need some help...i know the system may not be to eveyones liking but its there so i will use it,,,i was wondering how many gpm is needed w system, i think the boiler has a 7.5gpm max. it has a taco 009 pump. the system is feeding 6 zones ,4 of the zones are approx 300 ft each of 5/8inch pex in concrete under  pavers,the other 2 zones are 1/2 pex under steps and small walk way, the driveway is apprx 800sq ft..i recently flushed it all out and installed new gylcol. i have the re-02 remote on takagi and it is show the system flowing 2.1 gpm..that seems low, was thinking of going with a 0013 pump to try to get up to 5-6 gpm....any feed back would be great...    thanks <a href="">Reply</a> <a href="">Edit</a>


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    Got pictures?

    The use of well hung thankless water heaters as a hydronic heat source MUST be done in a primary/secondary piping arrangement, or you will see low flow conditions. The boiler pump (primary) needs to be sized for maximum allowable flow/pressure drop at the rated appliance capacity.

    The secondary pump should be sized to deliver a 30 degree differential in temperature, based on appliances output.

    Having more than a 30% solution of glycol will lead to the heat exchanger HOWLING when full fired, and can be alleviated by inducing CST50, which is a chelating agent.

    You will most probably condense the boiler when initially starting, and I do not think it is designed for condensing....

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • HDE
    HDE Member Posts: 225

    If you put 5 GPM + through a Takagi, the velocity through its coil will exceed 8 fps and the return bends will turn into sprinklers in no time. Tankless were designed to deliver momentary flows to open ended fixtures, closing the system and pumping at the higher flowrates wears them out quickly.

    You could pipe it primary/secondary limiting the takagi at 3 gpm and selecting correct pump for loops. In addition isolating the loops via a heat exchanger will improve the performance removing the glycol from the tankless.
  • fast1200gp
    fast1200gp Member Posts: 25
    thanks,but working what with i got?

    well thanks for the input as said in main post ,i purchased the house and this was a extra,,its in installed and only cost me time a the glycol to get it up and running,i know the system works as i have been here in winter and seen it work,so with that i know things may not be 100% but it works ,,with the 2.1 gpm is that enough? or should i up it with say a 0013 which will i think bring it up a few gpm...what will be i said,,just looking to get system working to it best with what i have,,,dont mind switching a pump or something but dont have time to do a system make over, thanks guys...gpm..what do u think is the number i need ? input ,,ideas?
  • kcopp
    kcopp Member Posts: 3,815
    I would not ....

    mess w/ it... if it worked that way, keep it that way. By adding more flow (0013) you could end up shortening its life more than it has been. Good luck.
  • fast1200gp
    fast1200gp Member Posts: 25
    how do i know what gpm should be?

    is that enough gpm? any idea?
  • fast1200gp
    fast1200gp Member Posts: 25
    going from ....

    taco 009 @ 2.1 gpm    to taco 0013 what gpm from upsizing pump?
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