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Should you install a pump on the boiler side of the 4-way valve

Weezbo
Weezbo Member Posts: 6,232
at the boiler return .....

Comments

  • David Van Wickler_3
    David Van Wickler_3 Member Posts: 63
    I wouldn't do it - what do you think?

    Here's a sketch of a proposed hydronic heating system with two 4-way valves. On the return to the boiler you'll notice a brazed plate heat exchanger that will provide stanby heat if the boiler should go down.

    I remember a great little piece of work explaining that the system circulator cannot provide flow in two directions.

    My theory is that the paddle in the 4-way valve must move in relation to the presure differential between the boiler side of the 4-way valve and the system side of the 4-way valve. The paddle in essence will move very little as the flow is diverted between the boiler side and system side of the 4-way valve.

    I'm obviously having a difficult time explaining this. Bt I see it as a system that will having a swinging water supply temperature due to the inability of the 4-way valve to modulate since the position of the valve paddle will move a small amount and possibly allow a large amount of system return water to mix with only a small amount of boiler water. This "valve authority" is attempting the impossible, that is figure out what position to be in and maintain a stable supply temperature.

    It's my belief (right or wrong) that for the 4-way valve to operate properly (and within the programming of the control) it should be located as close as possible to the outlet of the boiler, thus allowing a gravity flow drive throught the valve.
  • Constantin
    Constantin Member Posts: 3,796
    I haven't had a chance to look yet,

    ... but your sketch was huge... I have taken the liberty to resize it and show it below. In the future, you might do well to limit the width of your images to 600 pixels or less, otherwise we'll be hunting all over the screen to follow your diagram. Cheers!
  • Brad White_9
    Brad White_9 Member Posts: 2,440
    Pumping Away

    from the 4-way as you show looks entirely conventional to me. That is what I had for years with my Burnham 204.

    I have to assume that the 4-way is responding to maintaining a water temperature (indexed by OD reset or constant) and not by pressure.

    The circulator should be thought of as your dumbest friend in this case. It does not care what happens at the valve, it just wants to move water. The valve in rotating merely diverts that water to the boiler and in proportion from the boiler. The valve can recirculate 100% (bypassing the boiler entirely) or force all flow to go through the boiler, or any combination in-between.

    Unless I am missing something, that is what I see. Anyone else?

    BTW: Gravity Flow? I had a flow-check on the inlet to my Centra 4-way valve to prevent that. One could argue it was not necessary; I could never tell if it made a difference. Point being: the circulator was the motive force. In your case, with two circuits in parallel, you might consider flow checks or P/S arrangements so you do not have the circuits affect one-another.
  • hr
    hr Member Posts: 6,106
    Why?

    is the top 4 way even needed? looks like the boiler could live within those S&R temperatures/

    Personally I would do a P/s loop through the boiler and a couple Vs pumps. One as an injection for the low temperature system, the other as a delta t circ.

    This drawing looks German to me :) I believe the Viessmann biferrals run fine without a boiler side circ and a 4 way mix.

    Check out this website. This is some of the equipment AquaTherm will be importing. Looks like the use a thermostatic 4 way that allow gravity for boiler protection withouta circ? at least that is how I see it.

    Also the small indoor wood boilers with a fireplace look and small hydronic capacity.http://www.verner.cz/

    hot rod

    hot rod

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  • hr
    hr Member Posts: 6,106


  • Brad White_87
    Brad White_87 Member Posts: 24
    I thought the same thing, Hot Rod

    and figured he needed two different temperatures. The higher temperature to the HX I am just surmising, would be a design-day occurence and the 4-way would allow some re-set while the radiators have their own local volume control. Just my view.
  • Mark Hunt
    Mark Hunt Member Posts: 4,909
    Tekmar


    shows piping a 4-way with a P/S piping configuration.

    Primary boiler loop with pump, two closely spaced tees to the 4-way. Let the system pump pull through the 4-way and do not allow the boiler pump to push through the 4-way.

    Mark H

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  • Brad White_87
    Brad White_87 Member Posts: 24
    Good eye, Weezbo!

    I imagine you sitting up north basking in the 1:00 AM sun this time of year, alert to the small things. The return temperature would fluctuate but would be cooler than that I would think, depending on the radiation loop return temperature at a given time. Good call.
  • David Van Wickler_3
    David Van Wickler_3 Member Posts: 63
    page 176

    of "Hydronic Radaint Heating" a practical guide for the nonengineer installer.

This discussion has been closed.