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Adding glycol to heating system

Post in 'DIY and General non-hearth advice' started by SIERRADMAX, Dec 27, 2012.

  1. SIERRADMAX

    SIERRADMAX Feeling the Heat

    Joined:
    Jan 13, 2011
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    Loc:
    RI
    I've put this task on the back burner long enough and with cold weather anticipated next week, I have to add some boiler antifreeze to my heating system.

    I calculated the capacity of my entire closed loop system to be 7.7 gallons. Upon testing the system this summer, I smelled a bit of antifreeze but the test kit indicated freeze protection only to 32degF. I figure on pumping 2 gallons into the system should suffice. Mind you, I'll be tieing a wood boiler into the heating system in 2-3 months so I prefer to avoid a complete "drain" of the heating system.
    Can I do the following:

    1. Shut the heating system down
    2. Close the return valve and isolate the boiler from the remainder of the system.
    3. Drain 2 gallons from the boiler and pump 2 gallons of glycol while purging the boiler
    4. Then, open the zone valves/return valves while running the circulator a couple of minutes to mix residual water with the glycol?

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  2. Dune

    Dune Minister of Fire

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    Circulators do not actually pump, they just induce a flow. A couple of minutes of running the circ is pretty much useless for mixing purposes.
    You indicated you would be pumping the glycol in. Can you use that pump to mix the system? I am only asking since I have no idea what kind of pump you have.
  3. SIERRADMAX

    SIERRADMAX Feeling the Heat

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    So you're saying the glycol will just sit in the bottom of my boiler even if a circulator is running water through the zones & boiler?

    My pump is a hand pump with a hose bib on the suction end and a check valve/hose bib combination on the exiting side.
  4. Dune

    Dune Minister of Fire

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    No, I am saying a couple minutes with the circulator will not mix it. More like a half hour minimum.
  5. TheMightyMoe

    TheMightyMoe Minister of Fire

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    Fairbanks, Alaska.



    You can do it that way, I would just open all the zone valves, and leave the circulator. If all your zones are running at the same time, it will promote mixing.

    Did your glycol test healthy with test strips? Usually if you have to add more, you need more inhibitors, and it is a good time to add them.

    Was the cause a leak in the system? Or is the glycol going bad?

    I personally have my water feed valve turned off, so it does not add city water to my system, and contaminate my Glycol / kill my inhibitors.
  6. SIERRADMAX

    SIERRADMAX Feeling the Heat

    Joined:
    Jan 13, 2011
    Messages:
    290
    Loc:
    RI
    OK thanks fir the info. It tested healthy and ph was good but freeze protection was low. I picked up a bucket of Cryo-Tek non-toxic propyline glycol. It says it has inhibitors mixed in. 2 gallons will give me 30%. No leak in the system. I had my basement hydro-air unit moved 2 years ago and I think the HVAC tech who moved it didn't pump glycol into the system. Called him recently on it and explained I had a unit in the attic and his response was "I I didn't know"... I want to get protection over the next couple of months before the wood boiler install in which I'll either add that system to include glycol or install a plate heat exchanger to serve hot water/glycol mix to the attic AHU and keep the remaining system on strictly water. I can see some of my relief valves dripping. Must be from 10+ years of glycol exposure.

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