multi zone supply & return spacing 8"... 4" ??

Discussion in 'HVAC Heating & Cooling' started by hottubbrad, Dec 23, 2008.

  1. hottubbrad

    hottubbrad New Member

    Jun 9, 2008
    I am building a multi-zone hydronic system and am wondering how far the supply and the return lines (3/4") should be spread apart where they meet the main loop. I am using a 1-1/4" main loop and there are 6 zones coming off of it eash with its own Grundfos UPS15-58 circ pump.

    I have heard that the reducing tees should be no less than 8" apart. Some other site suggested 4". Can someone elaborate as to why this distance is important. I assume it is so that there is no crossover pull from the cold water side.

    What is the proper separation distance for the tees.....? How far apart can I put the tees and maintain effectiveness.??

  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    From the information you give, there is no way to answer. It depends on the type of distribution system and the type of tees. The basic answer, is that there must be as much resistance between the tees, (and neither 4" or 8" is enough in most cases unless they are diversion tees), as there is in the branch circuit, otherwise the water will flow directly past the branch without sending any water to the radiation.
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  4. nhmaster

    nhmaster Master Plumber

    Jul 30, 2008
    Tech. Instructor
    S. Maine
    The closer the better. remember that water always follows the path of least resistance. When you start getting over 8" then the path becomes a very short loop. You can not get them too close.
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