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  1. #1
    Join Date
    Jul 2002
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    Using automotive glycol in heating system

    I keep hearing words like "may, perhaps, could, etc". I have always heard not to use automotive antifreeze in a boiler and have avoided doing so. I went to a building and saw another contractor has put in (drums) of automotive antifreeze. I called the mfg and they say it's about 200 ppm of silicates. the boiler mfg has not returned my call. Before I go and make too many enemies I am wondering if this warrants removal and flushing of the system. Can I guarantee that it is not good for the system and why. Everything has to be in writing because lawyers may be involved. The auto glycol mfg told me they have a different specific product for boilers but wouldn't commit to it damaging their system.

    I read this under automotive but is this just another mfg pushing their product?

  2. #2
    Join Date
    Jul 2006
    Anytown USA
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  3. #3
    Join Date
    Mar 2007
    Sterling Heights, MI
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    From past experience, if the system was designed with the thought that a specific glycol was going to be used, the heat transfer factor for that glycol was figured into the job for heat transfer and hopefully compatability. If this is a retrofit from water to glycol, there may be more issues than you will know for a while to come. For one the pumps themselves will be pumping a different flow, the elastomer in the pump seals may not be compatable, the rubber expansion joints may not be compatable, the rubber seats in butterfly valves may not be compatable, the rubber in dielectric unions at coils may not be compatable, and the like.

    The name brand product specified on the hospital job by the architect for all new equipment was not compatable. Why, because two things. One the name brand glycol manufacturer gives a chart of compatability, but they do not do any of the testing for compatability, so who do you call now? The product manufacturer. Two, the chart lists only a few of the name branded products in a general form, so if you quickly go and look and find XXX brand, you say it must be compatable, when the specific type really isn't. Propylene glycol and etylene glycol are different, and they contain corrosion inhibitors engineered for a specific use. Brand XXX offers free annual testing for freeze protection, inhibitors and contamination if you use over a specific amount of their product.

    The hospital job in question required all butterfly valves from 4" thru 12+" to be replaced because they would no longer shut off. The is was both in the chilled water and heating hot water. The answer was valves that cost two times as much with Viton seats, oh and by the way are special order so no they aren't coming in next week. Seals blew out regularly before the compatable seals were installed. If you can't shut off the flow, you can't change the seal either, and then what do you do with all that fluid?
    The expansion joints pealed like layers and got sucked into the pumps and blocked flow. The dielectrics blew out over patient beds. Oh ya, glycol pumps like a milkshake because it is hygroscopic. The pipes will be dancing in the machine room. Vent the system and close the valves.

    We found this out after about five years. Who paid $$$? We did (the hospital), because they valve manufacturer prorated the amount of expected life left. And no, management didn't get the legal folks involved as maybe they should have.

    The old saying of pay now or pay later applies here. Ya some people will say but we will get the work, but maybe they won't. I was the Operating Engineer on staff that had to deal with all this and find the answers as well. The guy with the letters behind his name, if he spoke any amount of decent english or was a non experienced recent graduate, never knew what a catastrophy he had created for us and countless others.
    Better Service Through Knowledge...
    RSES, The HVACR Training Authority.
    UWUA Local 223

  4. #4
    Join Date
    Jul 2011
    East coast USA
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    What does your chemical company say that is treating the system? They need to know what they put in there and how is will effect the system. WOW i would never use auto in any commercial HVAC system.

    depending on the system and what its used for its either Ethylene Glycol or Propylene glycol.

  5. #5
    Join Date
    Nov 2011
    British Columbia
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    Certainly emergency circumstances will create crazy ideas, but when we have a choice to do the right thing as mechanics, we ought to.

    Here's a good article on the topic.

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