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air problems with baseboard zone

Darryl_3 Member Posts: 6
having problems with air on a first floor baseboard zone. had same problems last season as well. replaced air vent at the boiler tapping. it is a weil mclain CG4SPDN. purged the zone. do not have trouble with second floor zone. circulator is on the supply - TACO 007 with a flow check. expansion tank and fill valve are on the return.  the boiler runs 180 degrees at 20 PSI.

What could be causing air to to be continuously coming back into the baseboard zone?  Any help would be appreciated.


  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    What could be causing air ...

    ... to to be continuously coming back into the baseboard zone?

    If your circulator is on the supply, and your expansion tank is on the return, are you not pumping into the expansion tank instead of pumping away? Anything between the expansion tank and the circulator intake could be operating at reduced pressure. If your air vent is at reduced pressure, it could admit air to get it back up to atmospheric pressure. Why this air selectively goes into one zone rather than another I could not say.
  • Darryl_3
    Darryl_3 Member Posts: 6
    more info

    THANKS JDB, for your reply.

    Taking your advice into consideration. Want to add more detail about the job to rule out other causes.  The zone is 19 feet of baseboard that serves one large room.  The run is close to the boiler. Could the pump be too large causing the air problem along with a noise in the piping?  What puzzles me the most is that I have seen this system arrangement with the pump on the supply and the fill valve and expansion tank on the return and no problems.  Hoping to find another solution rather than re-pipe.  For now, I closed the air vent off with a ball valve to see how system operates.
  • Ironman
    Ironman Member Posts: 7,182

    Can you post some pics of your near boiler piping?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Hoping to find another solution rather than re-pipe.

    Remember I am not a heating pro.

    You might be able to use most of the piping as is (assuming it is otherwise OK), by plugging the tap on the boiler where the air release valve is located, and just putting the air release at the highest pressure point of your system. Actually, I would use something like a Spirovent or Taco 4900 separator. I imagine the point to put the air separator would be right after the circulator. The Taco separator does not require a straight section either before or after it. I do not know about the Spirovent. For best results, put the separator as close to the boiler output as possible, though at the output of the circulator.
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