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Old system - NO air separator

Dale_3 Member Posts: 58
All - We have a few buildings we work on that were built in an era where air separators were not installed, water was pushed through the HX's, the compression tanks are seemingly always water logged and it would appear we have "gotten by." I feel like we should be installing separators on these systems but once again I'm seemingly in the minority. Does anyone have any good thoughts I can possibly add to mine to help convince the powers that be that this should or should not be done?

Thanks in advance. Dale


  • Ironman
    Ironman Member Posts: 7,377
    There are two different ways to address air in a hydronic system:

    One is the old technology of air MANAGEMENT. This involves air being taken from off of the top of the boiler or its supply riser and directed to a compression tank like you have.

    The other is air ELIMINATION. This involves an air removal device like a Spirovent (a micro buble resorber) that removes air from the system. This type of system REQUIRES a bladder expansion tank because air is being REMOVED instead of being directed to the top of a compression tank.

    If you put an air elimination device on a system with a COMPRESSION tank, the tank will very quickly become water-logged and the relief valve will start discharging. You can NOT mix the two different technologies.

    So to answer your question: no, absolutely not unless you also convert to a bladder expansion tank.

    Is you're having issues with the present tank water-logging, then there's something wrong with your air management system.

    If you post some pics of the tank and near boiler piping, we may be able to help ID the problem.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    JUGHNE Member Posts: 11,074
    Do these compression tanks have sight glasses?
    The top valve can slowly leak air out, such a small leak it may never pass water.
    Bubble test the top air holding portion of the tank. Pinhole could also pass air and not water.

    Either repack the valve or shut them off. It worked for me.
  • jumper
    jumper Member Posts: 2,282
    I've seen different methods for air management in bigger buildings. An automatic air valve at top of system. And yes compression tank will eventually get water logged. Some owners pressurized the tank with compressed nitrogen. I thought it was over the top,yuk yuk,at the time. But decades later maybe it paid off?
  • Dale_3
    Dale_3 Member Posts: 58
    @IRONMAN Thanks for the input. No boiler here though. We are the cooling loop for our power plant.

    @JUGHNE Will look into sight glass leaks.

    @jumper I like the nitrogen idea.