Propylene Glycol Quandry

Discussion in 'General Discussions' started by jake72, Sep 12, 2011.

  1. jake72

    jake72 New Member

    I have recently started up my 3-ton Climatemaster Tranquility 27 heat pump. I have a horizontal loop field consisting of three 800' loops (2400' total) of 1" HDPE in individual trenches. I am running an non-pressurized system with a single pump QT flowcenter. So far, so good.

    I need to add antifreeze before the heating season begins. From what I have read, I am leaning toward using propylene glycol. But, the I'm seeing some conflicting information. Much of the propylene glycol I'm finding is "inhibited" to prevent corrosion and bacterial growth. However, Climatemaster recommends:

    "Only food grade propylene glycol is recommended to prevent the corrosion inhibitors (often present in ther mixtures) from reacting with local water and coming out’ of solution to form slime type coatings inside heat exchangers and thus hinder heat transfer."

    Does anyone have any recommendations on which direction I should go? Also, anyone have a supplier you can recommend?

    Thanks for your help!
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    My vote is for Methanol at a 20% solution and you do not have to worry about any of your concerns.:)
  3. This discussion has come up a few times in our office. For commercial projects we always go with PG. For commercial systems that utilize copper and steel pipe inside the building I would think the inhibitors area must. If you have an all plastic piping distribution system I could see where the inhibitors might not be critical. Methanol has has the benefit of more turbulent flow (higher reynolds number) and lower pumping power.
  4. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    I second the vote for methanol
  5. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    The only advantage to PG is.....nothing. Not heat transfer, not for the equipment, not for the enviroment. 20% meth solution in the ground is not classified by any national regulator as a hazard to the water table or anything else.

    Of course this doesn't prevent a few local agencies from uneducated prohibition.
  6. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    We switched from PG to Methanol 3 years ago, I cannot see any reason to go back.
    The inhibitors can make up a significant amount, thus most solution only contain 60% glycol to start with.
  7. Looby

    Looby Member Forum Leader

    A careful reading of Climatemaster's flow center installation manual
    (page 14) indicates that they consider PG appropriate (for residential
    use) only when local code prohibits the use of methanol or ethanol.
  8. zacmobile

    zacmobile Guest

    lake loop

    I am in BC and have been recently hassled by department of fisheries and oceans for a lake loop we did with methanol. So now they want us to pump it all out into drums and take it to a hazardous waste centre for disposal and replace it with PG. I questioned them if they had a list of approved and non-approved fluids for use in lake loops and they said they did not but they were working on it. I couldn't believe it!
  9. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Wouldn't want science to impede legislation......
  10. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    We switched to Methanol about 18 months ago on a majority of our systems. I have a current potential customer I am dealing with now that is very green and environmentally friendly. They have narrowed down our bid with another contractor and it sounds like they are basing their decision on the type of anti-freeze used based on environmental considerations.

    I explained the benefits of methanol but the other guy quoting told her PG is the only way to go and better for environment...I told her I would use either one she would like and design my system/loops/pump around their decision...

    Anyone have good environmental arguments for one or the other besides the basic ones?
  11. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader



    As they say, this is my ballpark. Was a contaminated sites Professional for 10+ years.
    The bad
    - toxic
    - Flammable
    The good
    - rapidly degrades in soil and water

    The bad
    -persistant (less mobile, less degradable)

    The good
    - non toxic
    - not ignitable

    If I chose a spill in water, it would be methanol. It would quiclkly surface and evaporate. Glycol would stick around and gum up fish. But you'd likely get in a lot more trouble with a methanol spill due to the toxicity.
  12. Looby

    Looby Member Forum Leader

    Another alternative...


    The bad
    - Flammable (until diluted to antifreeze strength)
    - slightly poorer heat exchange than methanol
    - more expensive than methanol

    The good
    - non toxic (essentially, weak vodka)
    - rapidly degrades in soil and water
    - much better heat exchange than p-glycol

    A worry-free ethanol source:
    - Waterfurnace Environol™ - denaturing agents safe for geo systems

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