Pex ground loop

Discussion in 'General Discussions' started by ABCO Heating, Jan 13, 2009.

  1. overlyhvac

    overlyhvac New Member

    pex

    Just as an example.... If you go to uponor website , which is wirsboro, it states that the reason to use it as a plumbing piping material is because of its high thermal resistence . So whithout even going any further in that discussion , or opening up the spec sheets or code books or IGHSPA manual would you install pex if it has a high thermal resistence in a ground loop ??
     
  2. ABCO Heating

    ABCO Heating Member

    20 deg difference from ewt to lwt

    My ewt is 42 deg and my lwt is 22 deg. Any suggestions? do i need larger circulation pumps to narrow the gap? I have 8 loops and i have the ability to shut them down individually, should i start shutting loops down? Any help is appreciated. Thanks
     
  3. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    In previous post you said you had 11 GPM, how are you measuring that?

    A 20° delta between EWT and LWT points to a serious low flow issue.

    If we use the delta of 20° and the probable HE of 30,000 this gives you a flow of about 3 GPM. 30,000/9600= 3.33

    If you really only have 3 GPM, your unit will function a lot better if you can boost your GPM.
     
  4. ABCO Heating

    ABCO Heating Member

    20 deg difference from ewt to lwt

    My ewt is 42 deg and my lwt is 22 deg. Any suggestions? do i need larger circulation pumps to narrow the gap? I have 8 loops and i have the ability to shut them down individually, should i start shutting loops down? Any help is appreciated. Thanks
     
  5. ABCO Heating

    ABCO Heating Member

    Tweaks

    With some tweaking I now have an EWT of 40 and an LWT of 28. I'm running at 11 gpm and I'm measuring that with a flow meter on the source return side of the W-W unit. I also have a 038 Envision W - A unit that is in parallel with this loop, However I have the valve's tweaked to only allow 4 gpm though that unit. This unit seams to only run when the outside temp gets below 5 deg F. at night and it will just help the in-floor heat through the night. If I shut the valve to the W-A unit i would then have 15 gpm though the W-W unit. I have noticed that i seem to be using alot of KW, my average has been about 120KW every 24 hrs. The house is a ranch with high cielings 10', 14' & 9', its 2450 sq. ft on first floor with in-floor heat thoughout, some in tile & some with a Watt's radiant Sub-Ray system under the carpet & hardwood flooring. The walkout basement floor is heated in concrete it is also 2450 sq ft. The garage is also heated in concrete it is 1000sq ft. I keep the main floor at 69 deg F., basement at 64 deg F. & garage at 48 deg. F. total of 3 zones. Any insight is appreciated.
     
  6. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Something is still not right with your data.

    12° delta * 11 gpm * 480 fluid factor = 63,360 BTU of Heat Extractioni from a 3.5 ton unit. This simply is not possible.
     
  7. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Why would you limit flow through the Envision 038 to just 4 GPM and run 11 GPM through the other. Are you quite certain of both flows?
     
  8. ABCO Heating

    ABCO Heating Member

    flowrate

    I have watt's radiant flowgaurd flow meters on the exit to each heat pump, I hope they are working correctly. I took some more readings just now and am showing 40 EWT & 30 LWT 11 gpm to 042 & 4 gpm to 038. 2 deg F this morning outside. Thanks
     
  9. ABCO Heating

    ABCO Heating Member

    More measurements

    Guys, I'm using a laser thermometor and I have been taking some more readings. I have been trying to find the best place to take readings and i think I have found the sweet spot. I am now seeing an EWT of 32f and a LWT of 27f giving me a delta of 5....calculating HE=C*GPM*(EWT-LWT). I am now seeing a HE of 28800 MBTUH. GPM is now 12.
     
  10. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    That

    sounds better.
     
  11. nile

    nile New Member

    where's the sweet spot? nt

    i measure the temp on the brass fitting but lately they are all frosty
     
  12. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Infrared may indicated incorrectly

    Especially when aimed at frost
     
  13. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    When they frost

    I use a cooper sh66 with western thermisters. I should buy a data logger with 8 inputs.

    The infra reds do not like frost or shiney, I carry flat black spray paint.
     
  14. ABCO Heating

    ABCO Heating Member

    Temp checks

    The sweet spot i found to be on the pipe inside the HP cover, but i also used Mark's tip with the spray paint and what a difference that made. Now it is very consistant with the paint on it. Thanks for the advice Mark.;)
     
  15. gabby

    gabby Member Industry Professional Forum Leader

    There is a new HDPE pipe out now for geothermal applications. One qualification to get that rating is the abrasion and thermal transfer properties (gas line used in many countries). This is called PE 3408 resin.
    The new resin called PE 100 has better abrasion and thermal properties because of the reduction in wall thickness. You will have to check PVC/polyethylene pipe manufactures to find it. It will ship at whatever lengths you request. In most cases there is a minimum number of coil lengths required per order. If you are doing three tons or more of cooling, I don't see that being a problem.
     
  16. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Gabby:

    Does this mean I have to start over?

    I like pex and pez.
     
  17. gabby

    gabby Member Industry Professional Forum Leader

    Nope...Buckeyes can use whatever they fancy with a history of working for them in their applications. Since then I found another one that is even better...but a little pricey. It will eventually replace all HD3408.
     
  18. jrh

    jrh Member

    I forget what is it about pex that IGSHPA doesnt like?
     

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