Expansion tank options

carbon neutral Posted By carbon neutral, Oct 11, 2012 at 11:24 AM

  1. carbon neutral

    carbon neutral
    Feeling the Heat

    Oct 1, 2007
    S.E. Connecticut
    I was reading another thread about sizing of expansion tanks and there was a link there to an Amtrol calculator. According to it I would need a AX-144. Since my system is basically the same as others, 1,000 gallons storage, and some say that the AX-144 isn't big enough by its self I may need more. OK price out a AX-144 ~$3,000!!!!! Yikes
    I am wondering why can't I just route a piece of pex from the top of my storage to the attic and have that terminate in the bottom of and tub? Is it concern of oxygen entering the system?
  2. JP11

    Minister of Fire

    May 15, 2011
    Central Maine

    I'm not a smart man, as forrest gump says.. but I know that.

    Look at daisy chaining smaller tanks.
  3. kopeck

    Minister of Fire

    Mar 24, 2011
    What JP11 said.

    You need volume, doesn't matter how you get there.

  4. nrcrash


    Apr 17, 2012
    I am installing 2 amtol 110 for my 1000 gallons of storage and it was about $1,000 from pexsupply.com
  5. mmudd


    Jun 7, 2012
    Central MO
    call amtrol. Thier website does not always come up with what will work.
  6. maple1

    Minister of Fire

    Sep 15, 2011
    Nova Scotia
    I'm using a 110 gallon propane tank I paid $70 for.

    Not 100% on how it will work over an extended period of time - but it's been working super fine for the short few days it's been online.
  7. carbon neutral

    carbon neutral
    Feeling the Heat

    Oct 1, 2007
    S.E. Connecticut
    As far as the oxygen entering. I have worked at several diesel powered power plants. All of them use an "expansion tank" at the high point of the system, that is where make up water is added. These tanks are open to the atmosphere and there is no problem with corrosion there. Also most steam plants have atmopheric drain condensers where condensate accumulates before being pumped back into a boiler. Again these tanks are open to atmosphere. Chemicals are used to aid in corrsion protection but if there was such a major fear of oxygen entering the system wouldn't these systems be closed? Even cars have expansion tanks that overflow into tanks that are open to the atmophere, then when the engine cools the coolant goes back into the radiator?
    I am just wondering if someone can explain how the fore mentioned systems get away without being closed and our home boilers cannot?
  8. Floydian

    Feeling the Heat

    Dec 12, 2008
    Southwestern VA
  9. Bob Rohr

    Bob Rohr
    Minister of Fire

    Jan 9, 2008
    SW Missouri

    It's the chemicals that are added, as you mentioned. Automotive antifreeze will sludge and turn corrosive when the inhibitors are consumed from the glycol antifreeze. That is why it is a good idea to check the ph and condition of the antifreeze from time to time. At a certain ph level it it time to power flush the cooling systems to prevent damage and reduced heat transfer.

    Over the years better inhibitor packages have been added to coolants and boiler treatments. Same with motor oils, they keep raising the flash point to prolong the life of the oils, and streach out the change interval. As engines operate at higher temperatures these days, coolants and oils have been improved. Better, more expensive brands of antifreeze and coolants generally have better inhibitor packages and last longer. The same with hydronic glycols and treatments.

    Most boiler manufacturers, steam included will give you fluid quality guidelines. Following their advise assures long life and best heat exchange. Many steam boiler installers flush them with a TSP or cleaner to remove the oils and assembly lubes and sealents, it prevents the water from foaming. This "soap" cleaning provides a good, slightly akaline ph for the fluid that is filled after the clean and flush.
  10. Jeff S

    Jeff S
    Feeling the Heat

    Aug 31, 2008
    For those that have the space and are able to support the weight of a non bladder tank with water in it may install it at the highest point of the system.This tank does not have to be open to the atmosphere.Siegenthaler shows an example of this in figure 12-2 in his book Modern Hydronic Heating.I've been using this system for 2 years,I don't have auto fill and haven't had to add water during this time.

    Dan Holohan also describes how Dead Men would oversize radiators on the top floor of a building and leaving airspace at the top of them for expansion.

    Siegenthaler also shows how you could use your storage tank for expansion as long as the top is the highest point in system leaving some head space,all piping needs to below the water line this can be found in figure 3-43 (2nd edition)or figure 3-69 (3rd edition).

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