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air separator

timo888timo888 Posts: 137Member
Recently a contractor pointed out that my furnace has no backflow preventer. Oil company says it only recently became a required component, and they installed my furnace before the code changed. I am looking to see what else they might not have installed. We have radiators, and it's my understanding that the system needs an air separator.

What I see immediately before the air expansion tank is something called a microbubble resorber-- is this the air separator?


  • RobbieDoRobbieDo Posts: 131Member
    Back flow Preventers

    Where I live it's code, especially if there is glycol in the system. Also, you have a boiler it sounds like, not a furnace. Do you have some pics of your system, that will help us more. Thanks
  • timo888timo888 Posts: 137Member
    edited March 2011
    air separator

    I am attaching two pictures of my system and a diagram from SpiroVent. Picture #1 shows SpiroVent and #2 shows PressureReducerValve. Unlike the diagram, these are on different "arms" (don't know the right term) on our Buderus. I can take other pictures if these don't show enough.
  • icesailoricesailor Posts: 7,265Member
    edited March 2011
    Air Separator/Bacflow:

    If you are on a municipal water system, you have always needed a back flow preventer. The installer was trying to save a buck. Or else, they are smart and the rest of us are not. Taco does NOT recommend that their wet rotor circulators be stood on their heads. Air will get in the head and no water will lubricate the rotor assembly. In fact, NO wet rotor circulator manufacturer of circulators allows it. At least Grundfoss and Wilo have vent plugs on the ends to get the air out. But that is in the horizontal position. Not vertical
  • timo888timo888 Posts: 137Member
    air separator

    Is it possible for the air separator's float valve to get stuck in the closed position because of mineral deposits? Can the customer test them to see if they're working?
  • IronmanIronman Posts: 4,934Member
    Mineral Deposits

    The only way that you could have enough minerals in the system to clog the MBR would be if you had a continuous leak on the system that has not been repaired and is causing fresh make up water to be constantly added.

    As far as the MBR functioning, unless you're having an on going air issue you shouldn't be concerned about it. I install an MBR on every boiler job I do, but it has the least amount of effectiveness on a system like yours where there are C.I. rads at a level above the boiler. In that case, the majority of the air in the system will rise to the top of the rads and stay right there until it's bled manually. The circ cannot get it back down to the MBR for automatic venting.

    What Ice said about the position of you circ is spot on. The upper bearing won't get proper water flow to lubricate it and you're gonna have a pre-mature pump failure. Get them to position your pump with the shaft vertical.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • Jean-David BeyerJean-David Beyer Posts: 2,599Member
    circ cannot get it back down to the MBR for automatic venting.

    According to Taco, and also John Siegenthaler, an MBR can eventually get air back down for automatic venting because the air will eventually dissolve in the water and get down to the MBR for elimination.

    See John Siegenthaler's "Modern Hydronic Heating -- Third edition" Chapter 13, pages 611 to 616, especially page 615.
  • timo888timo888 Posts: 137Member
    edited March 2011
    air separator periodic maintenance

    There are a few items that need to be addressed on our system after the heating season (install backflow preventer, rotate the circulator horizontal, install a shutoff valve for the air expansion tank) so maybe while the system is down I will clean the SpiroVent Jr or just replace it with a Honeywell Supervent which looks a little easier to service periodically. I found this thread while searching:

    "Almost all the systems I have installed need the vent cleaned out after a year or 2."

    We have had to bleed the radiators a couple of times, and the farthest ones don't get very warm.
  • IronmanIronman Posts: 4,934Member
    edited March 2011
    Air in C.I. Rads


    I have the 2nd addition of Siggy's and all the diagrams and explanations appear to pertain to baseboard rads or similar emitters. In which case the tubing is one continuous size through the emitter.

    A cast iron rad is a bird of another feather. Especially if it's connected to an old gravity flow system. In the former case, with the tubing being continuously the same, the velocity remains essentially the same throughout the loop. In that scenario, the circ is moving water through the emitter just like any other pipe in the system and dissolved oxygen is easily absorbed by the water and removed by the MBR as it enters it.

    In a c.i. rad, flow is being produced two ways: If it's piped across the bottom, the circ is causing flow through the bottom nipples, but not upwardly (path of least resistance). The upward and downward flow in the columns is being created by gravity due to the hotter water rising and the cooler falling. In effect, because the upper passage way is larger than the columns, the velocity slows at this point and oxygen in the water is released in the top of the rad. The top of the rad is doing in part what an MBR does: slowing the velocity down and releasing oxygen at that point. This is why c.i. rads need some means to vent them at the top of the rad.

    In fact, some old gravity systems did not have an expansion tank. The Old Timers would leave an air cushion in the top of the rads to act as the expansion tank. We just recently converted one of these. For further info on this type of system, see the attached articles:
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • IronmanIronman Posts: 4,934Member
    Bleeding Rads

    Do you know if your system was originally gravity flow? Some indicators would be:

    1. Original system pre-dates 1940

    2. Original pipes are very large - 2 - 4" diameter.

    3. Original system had a compression tank in the attic, or none at all.

    If your system is a converted gravity system, you may need some things checked / corrected to get flow to some of your rads.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
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