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Pressure in Water/Glycol Closed System

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Rob L_2
Rob L_2 Member Posts: 1
in THE MAIN WALL
I have a closed loop slab heat system in the field with approximately 40-50% glycol-water mix. When the boiler and pumps are running, the system runs about 30psi. When the system is off the pressure is about 12 psi.

Is this normal for a glycol mix system? Thanks in advance.

Rob

Comments

  • Unknown
    Unknown
    I assume

    you are reading the gauge on the boiler and that you are pumping away from the boiler and expansion tank.

    Your expansion tank is probably UNDERSIZED which is a very common mistake on a glycol system. The circulators and the tanks have to be sized for the glycol, most people will use water tables and assume they are the same (or forget).

    Regards,

    Steve
  • Rob L_3
    Rob L_3 Member Posts: 25
    Pressure in Water/Glycol Closed System

    Thanks Steve. Yes, we are pumping away from the expansion tank in the classic primary/secondary piping loop arrangemnt. We used the appropriate sizing charts and water tables to account for the glycol in the system knowing that it would create a more viscous liquid.

    I quess my main concern is this pressure spike a common occurence on glycol mixed systems?

    Thanks,
    Rob
  • Unknown
    Unknown
    look at the tank

    Rob,

    It is not common. All of my glycol systems run at the same pressure as my water systems. On snowmelt systems you have to allow for the greater temperature rise as well as the type of liquid.

    I am wondering if you have a bad bladder or air charge is wrong (too high).

    Steve
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