Expansion tank in closed heating system

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    • #274596
      MasterPlumbers
      Keymaster

      i know you must connect the sealed expansion tank to the cold feed but is it important that the air charging valve is up top and cold feed from the bottom or is it connected the other way round ?

      Please reply to peterf1@eircom.net

    • #290010
      Guest
      Participant

      A diaphragm (sealed) expansion tank is hung from the connection fitting and the air charging valve (if ever needed) is on the bottom. This way, air that could contain oxygen is expelled from the system rather than collecting and then leaving the unsealed part that would be below the diaphragm if connected so the tank is over the connection. You don’t want uncontrolled air to settle in spots and then move around.

      In a sealed heating system, it is not necessary to connect the expansion tank at the cold feed anymore. This used to be done with the non-diaphragm type tank because some of the fresh water air would collect in the tank as water entered the system. Using a diaphragm tank you want to move the air out of the system ASAP.

      It is more important to use the ‘pumping away’ concept published by boiler manufacturers for 50 years now. An explanation of this is in the free hydronic heating design lessons at http://www.hydronic.net

    • #290011
      Guest
      Participant

      The diaphragm (sealed) expansion tank is connected underneath on my heating system and it’s located next to the emersion in the second story of a two story semi detached house.It’s connected to the cold feed in the system. The house is 10 years old and apparently the heating system went wrong 6 months ago and the previous owners had the problem sorted.I dont know when the heating system was originaly installed. We are only in the house 3 months now. The attic was saturated so bad that even the insulation in the attic floor was replaced by the previous owner. We found all this out from the nice people living next door to us. Do you think the Expansion thank had anything to do with this problem and should i get a plumber to install the expansion tank so that the air charging valve is at the bottom.

      Very Worried
      Please Reply !

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