Discussion in 'Maintenance and Troubleshooting' started by don c, Feb 8, 2016.

  1. don c

    don c New Member

    I have some detective work needed - purchased a home with a new-to-me-geothermal system already present.

    The home was a foreclosure ... so the system was checked out and deemed working correctly with no other information avail. and as I learn more about the system questions are popping up ...

    I have spent about 100.00 on various testing hydrometers and refractometers as I was not sure what antifreeze I have.

    Here is my data:

    Standard hydrometer shows 1.046 specific gravity - this high # has been verified using more than one hydrometer ( the first hydrometer I picked up didnt even go that high and read off the chart !)

    Loop field is 20 years old - pond loop
    Furnace is newer with a low pressure B&D pump station - (side-note the original system was high pressure. )
    I have been thru 2 Ohio rough winters and the system has never thrown a temperature / pressure fault .
    EWT 30-31 degrees.

    I had a couple companies out that were not sure what was in the system. The company that installed the new climatemaster furnace stated Propyl Glycol - but I believe that was used to top off and they were not very thorough in determining loop size not did they use a flush cart to properly purge and re-fill.

    I do not see any data that would support a SG reading that high - except possibly GS4 which I dont believe is used much anymore. I think a 30% mix of Propyl Glycol should be about 1.027 or so...

    Certainly stumped and looking for input

    Is there anywhere to get my mixture tetsted to try and determine what is in there ??

    Thanks in advance for any input
  2. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Any reasons why you need to know right now.
    Since the system appears to run fine.....why the worry. If the suspicion is Glycol, what did the refractometer indicate?
  3. mtrentw

    mtrentw Active Member Industry Professional Forum Leader

    1.046 would be a 60% mixture of PG. If you've a refractometer, use it. If your reading is off the scale, cut it with equal parts water, mix thoroughly and retest to see if it comes down near 30%
  4. don c

    don c New Member

    Thanks for the reply gents !

    answers :

    well this actually all started as a request for a system check up last fall.... been working on this for a while to verify best system performance

    in my area - many HVAC contractors only work on the furnace side and want to refer to a drilling / loop specialist for the loop side. The loop rep stated he was not sure what was in there but suspected GS4 since it was an older system.... The loop "specialist" stated that he did not know how to test for GS4.

    I think this is a bit of the classic easy way out for everyone that has come to the house... including the original installer of the new climatemaster - the loop specialist wants to flush and refill with methanol which I am not opposed to at several hundred bucks cost- but overall the system is performing acceptable.. just wanted verify what I have and optimize performance .... seemed originally like a simple thought .... :)

    1) The system works OK - getting about 88 degrees out of the actual heating ducts in the kitchen - which is about 22 - 23 degrees over ambient ( therm settting at 68) have added a small amount of water to the system - maybe 1 gallon over 2 years which I hope was just air bubbles as the system needed service when I thought the house. also with a proper mixture I should get a bit better performance - correct ?

    2) My cheaper - 35.00 refractometer stated % of only 12% or about 25 degrees protection which does not make sense when I verified with the actual floating hydrometer. I believe therefractometer has a 60 degree testing temp which I am sure under - not sure it would effect the test result that much though ...

    By the way - this was just a large scale aquarium hydrometer ...... they are all the same right ?


    Don in Ohio
  5. mtrentw

    mtrentw Active Member Industry Professional Forum Leader

    Hydrometers are not ideal for measuring propylene glycol. Propylene Glycol cannot be read with a hydrometer reliably due to the fact that up to 70% concentration specific gravity increases, but above 70% specific gravity decreases. A 100% solution reads identical to a 40%.

    The truest test you can conduct is put a cup in the freezer with a thermometer and keep checking and stirring. You'll find the slush point.
  6. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Never change a winning team!

    While i would prefer Methanol in general, I would not refresh the loop unless there are issues with the glycol (Slime buildup, bacterial growth etc).
    Usually, the refractometers are fairly precise.
    Many lesser knowable installers are getting the glycol from supply stores and are not aware of the fact that they only contain 60% glycol, the rest are rust inhibitors etc. and need to be accounted for. Thus the actual glycol concentration is significantly less.
  7. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    Put in freezer and see when it starts to slush!
  8. don c

    don c New Member

    I like the test in freezer idea ( ... not sure if the wife will be as excited as me...!! ) .... will try that. Hopefully freeze / slush point looks good, as I would sorta be back to point one as to what to add (without knowing what is in there ) so as not to mix different products... which I am sure would not be a good idea. ..

    I suppose I should just consider a flush at some point with as old as the system is ....

  9. mtrentw

    mtrentw Active Member Industry Professional Forum Leader

    If you can get to 20* before slush, I'd call it good.
  10. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Pull some fluid and put it in the freezer. That will give you a clue on freeze protection.

    I have a guy in Strongsville who can get it tested.

    I am in your area and I work both
  11. don c

    don c New Member

    **** update ****

    Slush test shows partial mystery solved..... I show signs of jelling and freezing at about 24 degrees - which is about exactly what the refractometer stated. Last year I tested EWT at 31.5 and LWT at 26.5 on a cold day January of 2015

    I reckon that I should get a better mix in the system - How cold have some of you seen the system get ? I understand you want about 15 or so degrees below your anticipated EWT .... but any one have some "real world" cold side temps ?

    Thanks again for all the advice ....
  12. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    The coldest place is the heat exchanger, not the loop. The heat exchanger will freeze first. Again, likely Glycol, likely a glycol brand which suggested 100% percent glycol but only contained 60%.
    It rarely drop much lower than 30F EWT because of the phase change. So your 26.5F LWT might be right on the edge.
  13. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Here goes, it is going cold. Doc, is correct the coldest spot in your system is inside the co-ax barrel.

    I tend to protect my systems to 25* below what I expect in the unit for a low temperature.
  14. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    So what temps would you protect it to? Do I get this right, that you would protect the system down to zeroF if you expect a minimum LWT of 25F?
  15. arkie6

    arkie6 Active Member Forum Leader

    Here is what Climatemaster says about freeze protection:

    "Freeze protection should be maintained to 15°F below the lowest expected entering loop temperature. For example, if 30° F is the minimum expected entering loop temperature, the leaving loop temperature would be 25-22°F and freeze protection should be at 15° F (30° F - 15° F = 15° F)."
  16. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Our Canadian codes state 6C (9F) below design temperature? I think that's the value - just not in office right now. Nobody ever knows their design temperature though, but that's what we do for our systems.

    edit for correction: "the heat transfer fluid shall provide freeze protection to at least 5C (9F) below the minimum loop-design temperature."
    Last edited: Feb 12, 2016
  17. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Chris helps make my point.
  18. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    OK. In heat dominated climate like Northern Ohio, assuming that your design for EWT is around 30F and your LWT is around 25F, you still want to protect your loop down to 15F, meaning 15F below EWT and 10F below LWT. Which is the recommendation for Waterfurnace and Climatemaster.

    To be clear, loops never freeze, it is always the heat exchanger which is the closest part of the system. In order to pull heat out of 25F leaving water the heat exchanger by definition has to be colder. Your flow might be off by a couple GPM, now your LWT is 23 degrees instead of 25F and the metal surface at the end of your heat exchanger now is 20F. Now you have a more severe winter that design assumption. 15F below EWT is really the protection standard most manufacturers ask for.

    Chris, I assume with minimum loop design temp they meant LWT?

    Also Glycol is a bit more forgiving, Methanol freezes rapidly.

    Edit: I had the heat exchanger freeze with 19% methanol (17F freeze point) and 24 degrees LWT. So my installer being a couple percent off in the calcs created scar tissue for me.
    Last edited: Feb 12, 2016
  19. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I do not wish to replace frozen equipment. I do not want my customers scared. Manufaturer's minimums are set by humans.

    Do you cancel your liability insurance because you have never made a claim yet?
  20. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    It appears that you are human as well......

    You don't seem to understand the impact of unreasonable amount of antifreeze on pressure drop, turbulent flow, and heat transfer capability. What you suggest makes systems inherently inefficient.

    Pressure drop: For the sake of this discussion, you have a 3 ton system needing 3 wells of 150ft and have 0.75" pipe. With 32F water your pressure drop is 10.7 ft of head, and your reynolds number is 7956, very much turbulence, were Reynolds of 2500 should be a reasonable number for adequate turbulent flow.
    Now use 21% methanol (15F freeze point) in the mix and your Reynolds number drops almost in half to 4048, and your pressure drop goes up to 12.6 ft/hd.
    With 25% glycol (15F freeze point) and your Reynolds number drops down (below 2500) to 1878 and you have laminar flow, and your pressure drop is up to 15.4 ft/hd.
    To protect down to 5 degrees, what you suggest, you need 35-40% glycol, with a reynolds number of around below 1400, and a pressure drop above 20 ft/hd.

    Heat transfer: Going from 25 to 35 % glycol levels will transfer about 5% less heat

    You are now getting out of the range what a single 26-99 pump can do, thus you would need to almost double your pumping power to have enough flow through your loop field.

    I yet have to see a frozen coil which bursted, usually the heat pump's safeties kick in before. The Manufacturer's recommendations are there for a reason, and they are the same across manufacturers. Protect your loops down to 15F LWT, below that your freeze protection will kick in anyway and stop the compressor. No reason to kill the efficiency.
    If you don't want your customers to be scared, don't be scary!

Share This Page