Expansion tank sizing

Discussion in 'HVAC Heating & Cooling' started by rockycmt, Sep 30, 2008.

  1. rockycmt

    rockycmt New Member

    Messages:
    129
    Location:
    New York
    Can you help recommend a brand/size expansion tank for my HW system.

    I currently have one but it is a large, old, steal, bladderless tank recessed in the ceiling. I need to remove it anyways cause I have to sheetrock around the boiler so I am deciding to replace it.

    I have a 4 bedroom 2000 sf cape
    Full basement
    2 bath

    http://www.watts.com/pdf/1915356.pdf
    Last edited by a moderator: Oct 27, 2008
  2. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Nope. Need to know volume and head pressure.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    Watts has a calculator on their website you can use. You'll need to know some stats for your heating system to get it right.
  4. rockycmt

    rockycmt New Member

    Messages:
    129
    Location:
    New York
    Do I only need to take into consideration the volume of my boiler or all the piping as well? If so, how do I estimate the 1' copper lengths throughout the house?
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    You need the total volume of water, since all of it can expand and contract. Volume of a cylinder is pi*r^2*length. If you get a guess at the total length of pipe, you'll be close. But, I assume those pipes run to radiators? Unless they are finned baseboard, they'll add some. If you get a good approximation, the tanks have a fair range, you should be able to properly select one. there are 231 cubic inches in a gallon.
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