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Air in baseboard system

zepfanzepfan Member Posts: 287
The photos attached is of a

system is a seven zone basboard heat system with three boilers. There is a total of 11 circulators. One for each boiler, one for each zone, and one main system circulator. There are no zone valves. Over the last year three circulators have been replaced. When the system was purged of air, the building heated fine. About three weeks after that, the building was not heating, and it appeared air was the issue. The air was purged again, and the building heated fine again. That was the end of last winter, and so far this winter, it has happed once where the system needed to be purged. We are using the same procedure to purge the air that is shown in the the instructions that are shipped with Taco circulators where the water is sent through a zone at near city water pressure, the isolation valve on the return side of that zone is closed, and the boiler drain located in front

of it is opened, and the air is purged from the zone. This seems to keep the system going for a few weeks, and then it needs to be done again. Any suggestions would be much appreciated. Thanks to all.


  • neilcneilc Member Posts: 804
    with everything turned off, the boilers and circulators, and all those ball valves open,
    what's your static fill pressure ?
    how tall is the house or building? how many floors?
    air is getting in somewhere, where?
    next time you think you're fully purged, try closing that vent on that scoop and see if that helps.
  • SnowmeltSnowmelt Member Posts: 1,168
    that scoop is useless you need better air purging i myself like the taco 4900
  • bob eckbob eck Member Posts: 908
    Put in a Taco, Spirovent or Caleffi air eliminator.
    The expansion tank in the photo is that the only one on the system? Is that tank large enough?
  • DZoroDZoro Member Posts: 1,032
    Agree with Bob, that tank seems small for that system? The middle 2 pumps have a lot of corrosion between the check valves and pumps. Is that leaking there, or possibly pulling air in at the corrosion. Hard to tell from the pics how bad it is.
  • zepfanzepfan Member Posts: 287
    I want to thank everyone that responded to this post, and apologize in the delay in responding. So far, so good as it has been almost a month with no issues. The static fill pressure is 22 psi, and the height on the largest heating unit above the boilers is about 25 feet. With all pumps on, and the system up to temperature the pressure goes to about 26 psi, which should be more then enough to reach the highest point. I agree the air scoop is useless and a better air purger is necessary. I am going to keep my eye on it. Thanks to all
  • Intplm.Intplm. Member Posts: 1,086
    Suggest you replace the air scoop with a micro-bubble air separator. Install another or larger expansion tank.
    Get rid of the hy-vent on top of the air scoop and any place else that they are installed. These things can, when worn out actually suck air into the system, and not expel it as designed.

    You surely have a leak that is small and is triggering the auto feed to add more cold water gradually. Micro bubbles from that new feed water is contributing to your problems.
    From your pictures , this is most likely the source of the continued air problems that you are describing. The hy-vent(s) and added water.
    Replace these as suggested and you should have the described problems go away.
  • SuperTechSuperTech Member Posts: 1,210
    I agree wholeheartedly with the post above. Remove Hy-vents and replace the scoop with a microbubble resorber, you won't have any further problems after the initial purge. I'm thinking the Hy-vents on the return is your most likely culprit.
  • Intplm.Intplm. Member Posts: 1,086
    Would be best not to replace them with another hy-vent. Better to use a spirovent hi-top.
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