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Snowmelt return temps??

fast1200gp
fast1200gp Member Posts: 25
in Radiant Heating
What should the return temp be on snowmelt system.glycol  4-zones 300 ft 5/8inch pex each .pex in cement slab 1-2 inches with pavers over top

Comments

  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited October 2011
    What's

    The supply temp? What's the glycol mix ratio? How many btu's am I delivering? What size is my pump?

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  • fast1200gp
    fast1200gp Member Posts: 25
    takagi tk1s

    Right now there is a taco 009....but gpm seems low ..only at 2.1 gpm...was thinking of upsizing pump to 0013?
  • fast1200gp
    fast1200gp Member Posts: 25
    straight hercules cryo-tek..

    original type  ..its already diluted from them,,
  • CMadatMe
    CMadatMe Member Posts: 3,086
    How Do You

    Know what size pump? Did you do a design to calculate flow required and ft of head? You do realize that you need about 120 btus sqft to do snowmelt dependent on what part of the country you are in.

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  • fast1200gp
    fast1200gp Member Posts: 25
    the house

    i recently purchased had system in it...just trying to get it running the best i can for what it is...the takagi is a 190,000 btu heater, i feel the gpm is very low,,and would take very long to heat ,,,this is all new to me,,,i knwo there are way better systems but this is here why not get it to work the best it can,
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Big Pump

    Your going to neeed an awful bignpump



    5/8 pex on a 50% mix flowing 2gpm of 120 degree water is 20' of head. My head loss calculator for Pex doesn't even give you a 100 percent fraction. We design for a 30% mix.



    How many sqft are you trying to melt?

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  • fast1200gp
    fast1200gp Member Posts: 25
    driveway is

    about 800 sq ft..diluting the gylcol isnt a  issue,but  would think it would make that much of a flow diff from 30% to 50%
  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited October 2011
    800 Square

    Just ran it for you. Based on 0 degree climate getting the surface temp to 35 degrees using a 30% glycol mix. You need 140'000 total btus



    Tube Spacing 6"

    6 loops of 287 ft

    Flow rate 11.6gpm

    Head Loss 16.3ft

    Water Temp 112 degrees

    Design Temp Drop 25 degrees



    Ran it with what you have:

    Tube spacing 9"

    4 loops 300

    flow rate 12.4

    Head loss 37.4' ( still 30% mix)

    Water Temp 134 degrees



    So you need a pump that can move 12.4gpm @ 38' of head providing you dilute. Your out of any curve from any Taco 00 pumps. 0013 maxs out at 25' of head at 12gpm You getting all the 009 can do.

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  • fast1200gp
    fast1200gp Member Posts: 25
    will the 0013

    be better?...where do u think that will put me @ gpm wise,  comparing to the 009?..any idea? the 009 is at approx 2.1 gpm
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Off the Curve

    The 009 has a steeper curve. You would be off the curve on a 0013. Your going to need a big pump. If you can't move the required gpm its going to be a very costly and inefficient system.

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  • fast1200gp
    fast1200gp Member Posts: 25
    to get 7 gpm

    what pump 115v u think would work??  that could switch right out for 009..i dont think the takagi can flow more then 7.5 gpm....so atleast if i can get it close to that im in the right direction,,,i plan on changing system around at some point,but for now just would like to up the gpm and get it working a lil more efficent,,,any ideas on a pump? grundfos? taco ... thanks alot for the help
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Head

    based on the ft of head you are dealing with, nothing in the small residential size pumps.

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  • fast1200gp
    fast1200gp Member Posts: 25
    what do you think the 0013

    would flow?....less?.more?..same
  • fast1200gp
    fast1200gp Member Posts: 25
    or grundfos

    up26-120u
  • fast1200gp
    fast1200gp Member Posts: 25
    hey chris.what do u think

    about the grundfos 3 speed

    UPS26-150

    F/SF

    A lil pricey but may do trick?...to much?...guy's?
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Taco Pump Curves

    As you can see from the attached the 009 is actually the best pump. It can atleast move some gpm at the head you have. Your looking a installing a light commerical pump more like a Grundfoss UPS 32-160/2. Pump probably costs more then your water heater.

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  • fast1200gp
    fast1200gp Member Posts: 25
    yes i have seen

    taco curve chart...thats y i thought the UPS26-150

    F/SF  looked to be a good choice ,,figured it would get me up around 5-6 gpm..
  • Ironman
    Ironman Member Posts: 7,510
    What You're Missing

    Is the high head through the Takagi. At least 12' @ 6gpm if memory serves me right. Maybe higher. That would have to be added to the 37' of head that Chris calculated for the loops.



    You're also over-looking another issue: velocity. Even if you could  find a pump that would give you 50' of head, the velocity through the Takagi would be so high that it would erode the heat exchanger very quickly.



    You need to pipe it primary/secondary so that both the heater and the loops have the correct flow. Then you can use two standard circs. This would be cheaper than trying to cram a monster circ. in the system which wouldn't work properly anyway.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • fast1200gp
    fast1200gp Member Posts: 25
    How is that done?

    Can u explain? thanks for the rply.
  • CMadatMe
    CMadatMe Member Posts: 3,086
    What Iron

    is talking about is that the unit needs to be piped primary secondary piping. The pump I chpicked is for the snowmelt system only.

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  • fast1200gp
    fast1200gp Member Posts: 25
    Any pics ?

    of something like that,,can that be done with a takagi as the boiler?sorry this is new to me but im learning fast,,,just want to get the system running as best i can b4 the snowfall,,,next yr i will invest more $ and time,,,i dont mind putting a few dollars into it now.but dont want to do a major over haul...thanks very much guys..i open for any useful advice.
  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited November 2011
    Like This

    http://noritz.com/u/1a_nh1501_2001_dv_hydronic_only.pdf



    You would add the snowmelt pump to the out to heating system side. This diagram is for concept only as it is for another tankless mfg.

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  • fast1200gp
    fast1200gp Member Posts: 25
    confusing..........

    ugh!
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Sorry

    Just giving you the correct and best advice. Think of it as finding lost money because if you do it right the checks to the gas company will get smaller.

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  • fast1200gp
    fast1200gp Member Posts: 25
    i know that..

    can i do it with the takagi system i have,,...from the outlet manifold and return manifold all should be good,
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Post Pics

    Can you post some pics of the install?

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  • fast1200gp
    fast1200gp Member Posts: 25
    its a pretty basic set up

    takagi. out to the pump to the out manifold back into the return manifold, ,,just basically a big loop from the takagi,the pump is after the takagi, so it pushes the glycol threw the system then to the takagi,,,,make sense?...there are some valves and ball valves etc ,,but thats the basic set up...i know from the manifold's out and back is correct,,,just the takagi set up needs some changing,,or pump set up..just with 2 gpm even going out @ 180 degrees,,its goona take a while to heat up..
  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited November 2011
    Take

    The concept from the diagam I posted. The existing 009 pump becomes the boiler pump as in the diagram pumping towards the heater. Install 2 closely spaced tees as in the diagram and add the Grundfoss pump I gave you to the out to heating system side pumping towards the manifolds. Expansion tank and feed valve are installled as seen in the diagram. Its upmto you to add ball valves, temp gauges, etc.



    You may now need a circulator relay but would have to see your units electronics to provide you with any wiring and control advice.

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  • fast1200gp
    fast1200gp Member Posts: 25
    sorta got it

    what about top of diagram,,what the make up water line?...and where is second pump in picture,,,
  • Ironman
    Ironman Member Posts: 7,510
    Primary/Secondary

    See page 3 of the attachment for a diagram.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • fast1200gp
    fast1200gp Member Posts: 25
    i just have 1

    out manifold and 1 return manifold   just a loop..what am i missing?  whats the other line going to? one says secondary circut,,,whats the other going too after the t's w the D on it,,,
  • Ironman
    Ironman Member Posts: 7,510
    2 loops

    The "D" could be going to your radiant loop with the loop off the bull of the Tee's going through the Takagi, or vise versa. It will work either way. If the loop to the radiant requires a larger pipe than the loop to the boiler, then the radiant would run straight through the Tee's. Whatever requires the larger pipe goes straight through. Got it?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • fast1200gp
    fast1200gp Member Posts: 25
    No...im confused...

    can u draw it out for me?....from takagi inlet outlet to the in and out manifold,,,,sorry just confusing and new to me ..thank you
  • Ironman
    Ironman Member Posts: 7,510
    Imagine...

    The "U" bend in the secondary is the Takagi; "D" on the right of the primary connects to the supply manifold; the return manifold connects on the left side of the primary, before the circulator. It's that simple. Connect the makeup and expansion tank up stream of the primary circ.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    I wouldn't do the make up...

    Eliminate the make up connection, and install a low water cut off and a low pressure cut off. Otherwise, you may get inadvertent dilution of your glycol, and then ALL of the tubing in the slab may freeze and break and then it is really trashed...



    This recommendation applies to ANY hydronic heating system with glycol in it.





    Proceed with caution. Also consider placing a Glycol PIG on the system to avoid pressure drop during initial start up and deaeration.



    http://www.heatinghelp.com/forum-thread/136433/glycol-feeder-and-mold



    Look at the picture.



    ME

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  • Ironman
    Ironman Member Posts: 7,510
    Great Idea, Mark

    I normally just keep the shut off valve closed on the fill line and have the H.O. monitor the gauge. I like this setup much better.



    I' ve got a job with 8,000 ft. of snow melt that we'll be charging with glycol and starting in the next couple of weeks; I'm gonna use your "pig" design. Let me know if I owe you any royalty for it. :)



    Thanks for sharing your ingenuity



    I love "The Wall". Learn something regularly here.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
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