Pex ground loop

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

  1. ABCO Heating

    ABCO Heating Member

    Does anyone have experience with putting in a pex ground loop? I seen a report that is stating it now to be superior to HDPE pipe or at least just as good. No fusion joints need because all lines are home ran to the inside with no joints needed.
     
  2. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    I don't know how the conductivity stacks up against HDPE. Is PEX available in the required diameter at a reasonable cost?
     
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    I won't bash PEX

    But our codes don't allow it in Canada.
     
  4. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    I have heard about using PEX, never seen it
     
  5. ABCO Heating

    ABCO Heating Member

    I have 8 pex loops @ 600ft each 5 to 7ft down in damp sand, my EWT is 48f & Lwt is 32f. Seems like its working good. Trenches are 4 feet wide & 300ft long each, they are about 8' OC. I spent about $3000 on materials for loop field. I had a question about pressure drop, can anyone tell me what it should be? My loop is charged to 55psi and I have an Waterfurnace EW042 water to water unit. Thanks
     
  6. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Pressure drop in pex

    should be availible from the manufaturer.

    How was the loop pump sized?

    I see very little here on sizing pumps. I would find the head loss through the loops and the manifold and add the loss through the equipment. Added together and applied to a pump curve will allow the smallest possible pump to do the job.
     
  7. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    A 16° drop in water temp through the heat pump seems to indicate low flow though the heat pump.

    I have a 6° drop through my heat pump

    How many GPM's are you getting through the heat pump?

    Which pressure drop are you looking for:

    Through the heat pump or through the ground loop?

    We need to know the flow before we can calculate the pressure drop.
     
  8. ABCO Heating

    ABCO Heating Member

    GPM

    I have 11 gpm going through the heat pump, I will get my pump model #'s of circ pumps tonight tonight to help us calculate.
     
  9. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    what size is your heat pump?
     
  10. ABCO Heating

    ABCO Heating Member

    Pumps

    I have 2 Grundfos UPS 26-99 3 speed pumps in series to my loop. 1 is on Medium & the other on low. I'm pushing 11 gpm through the heat pump. Then manufacture recomends 11 to 16 gpm. Will i get better effeciency if i turn up the pumps? Thanks
     
  11. ABCO Heating

    ABCO Heating Member

    pump sizing

    I have 2 Grundfo,s UPS 26-99 3 speed pumps piped in series giving me 11 gpm thru the HP, 1 is on low & 1 on med. Waterfurnace recomends 11-16 gpm for my unit. If i bump up the gpm will it be more efficient? Thanks
     
  12. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Something is out of whack

    Your numbers are 11 GPM at 16 Deg F Delta T through a Waterfurnace EW042.

    That (11*8.33*60.0*16=87,965) works out to over 7 tons actual heat extracted from a nominal 3.5 ton unit.

    Something isn't right about these numbers unless you have TWO of the Waterfurnaces in series
     
  13. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    The lower gpm's are for EWT around 50°

    The higher gpm's are for EWT around 30°

    The manual should tell you how the gpm will affect the efficiency.
     
  14. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Dewayne,

    Did my calc make sense to you?
     
  15. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    We both posted at the same time and I didn't see your post :eek: :eek:.
    Yes you are right, there is a problem. Either the gpm is wrong or the delta T is wrong. There is no way that a 3.5 ton unit can extract that much heat.

    I thought the 16° was suspect, just never did the math.

    Thanks
     
  16. overlyhvac

    overlyhvac New Member

    pex?

    what make , size and type of pex?


    not an accepted burial pipe or geo pipe , have you ever seen a plumber run pex underground water lines?????
     
  17. dbelisle

    dbelisle New Member

    Check the price between HDPE and PEX and you will find
    PEX is a lot more money.....

    There is no advantage to PEX , It will cost a lot more , and
    no manufacturer will stand behind it for a loop ,but it would work ...

    Dave in NH
     
  18. ABCO Heating

    ABCO Heating Member

    Geothermaldiy.com

    Hmmm.. Well this guy (geothermaldiy.com) is selling complete PEX loop systems including loops, manifolds and flow centers. He is a dealer for Waterfurnace & Florida Heat pump. Are you telling me that when you buy a system from him you don't get a Warranty on the equiptment??? Some how I find that hard to believe. I will have to contact him to check on the warranty, but i can't see them allowing him to be a dealer if they would not warranty a system with a PEX ground loop.:confused:
     
  19. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    PEX Groundloop

    Ignore the detractors at you own risk. Many of us on here have years of experience in this industry and when we say we've never used PEX for ground loops, there is a reason for it.

    I'm just a little tired of folks thinking they'll save money in such manners. Granted, you can save money by buying a $200 car, but you'll get what you pay for. And in this case, HDPE isn't even expensive, so there is no reason to avoid using it except for resisting paying someone to fuse and pressure test it properly.
     
  20. ABCO Heating

    ABCO Heating Member

    Temp check

    Thanks for the calculations, I will recheck my ewt & lwt so we can rerun the numbers. I will use a different probe this time. Thanks again
     

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