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Pumping away from the Compression Tank, on a Primary-Secondary heat system

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bloombrewing
bloombrewing Member Posts: 5
edited December 2021 in Radiant Heating
Most all the pictures I see of a Primary-Secondary system, with close-spaced tees, always seem to show pumping towards the expansion tank, not away. Dan Holohan has a book on "Pumping Away" but all I see is towards.

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  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,005
    edited December 2021
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    I can't speak for anyone else, but I would have connected the x-tank to the bottom of the air eliminator.

    Also, are those swing check valves on the suction side of the pumps? On the vertical?
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • bloombrewing
    bloombrewing Member Posts: 5
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    This is a picture from www.radiantcompany.com, not my job
    It does appear that they are single-swing checks before the pumps on the vertical
    I agree with putting the tank on the bottom of the air separator, but I often see similar setups like this picture, and wonder????
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,540
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    @bloombrewing you should always pump away from the expansion tank if at all possible. With primary secondary the expansion tank should be on the common piping not the boiler loop
    bloombrewing
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
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    It's worth remembering that not all photos are the best way to do things. Also that there are a number of ways to do things which work -- just some work better than others.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 22,158
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    Is that a tankless water heater? Usually with high pressure drop appliances you want to pump into it

    judging by the Y strainer you are pumping out of the heater?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • rsilvers
    rsilvers Member Posts: 182
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    Why so many drains? The Pumping Away schematic only has one at the boiler outlet.
  • bloombrewing
    bloombrewing Member Posts: 5
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    Yes, there seems to be unneeded drains, or purge ports. The 2 at the heater would be to service the heat exchanger when cleaning. The 1 on the "drop" at the Return manifold would be to purge the two zones of any air. The 2 that are before and after the air-seperater and the one near the pumps, I have no idea why they are there and really not needed. Not my set-up, just a picture taken from a Heating supply web site.

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