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Zone valves - on supply side or return?

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Looking for an answer to this question: Should zone valves be installed on the supply side of the zone or on the return, and why? Pros and cons, etc. All feedback is appreciated.
papascaseras26

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  • mjcromp
    mjcromp Member Posts: 57
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    Where do I put them

    I put them on the return side. I see them on the supply side sometimes. I don't see any differences between the two. That is just where I prefer to put them.

    There was an error rendering this rich post.

    papascaseras26
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    edited February 2014
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    Normally, on the return

    A ball and seat type of valve (Honeywell for example) can bypass in certain applications of high head pumps when installed on the supply with the pump on the supply side.



    The return also represents the lowest fluid temperature, which extends valve life expectancy.



    If it is a ball valve type of valve (Taco Sentry) it could go on the supply and not present any bypass conditions.



    ME

    There was an error rendering this rich post.

    papascaseras26
  • hot_rod
    hot_rod Member Posts: 22,262
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    Return

    has been my method, but if all the zones are takeoffs from a horizontal header above the boiler, with the piping going up, you could get some ghost flow without positive shutoff on all the supplies. In that case the valves installed on the supply might be better.



    Even high Cv flapper style valves generally have a 20 psi shut. Up to 75 psi shutoff on low, 1 or 3 Cv valves.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • NYplumber
    NYplumber Member Posts: 503
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    Check valve

    Do you guys put a check valve of any sort on the supply if the zv is on the return? I am lead to believe any pipe diameter over 3/4" will migrate flow due to enough room in the pipe to flow two ways based on the buoyancy of the liquid.



    On another note, a trend I see as of late is plumbers zone with pumps and use a zv after the pump. To me its job security.....and not the way my company conducts business. When I asked a plumber recently he replied that check valves pass water. Its my belief that he isn't a good heating contractor.
    :NYplumber:
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
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    Rare occurrence...

    Especially with a complaint attached.



    If it is a problem, a flow check valve is recommended, right at the supply main of the heat source.



    I can only think of one situation where it has been an issue, and that house had a convector directly above the heat source (CI boiler) and when it was done doing DHW, the residual heat would rise up out of the boiler. Fixed it with spring checked valves.



    ME

    There was an error rendering this rich post.

  • PLUMMER
    PLUMMER Member Posts: 42
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    Preference

    We have mostly done supply side here in this area, but I personally pipe whichever will be more aesthetic. I completely agree with ME on the lower temp longer life.

    Almost all old timers here did supply side and this eliminates any ghost problems. Most systems are also small and the only time we see a circ over come a ZV is when someone uses much too large of a circ. a differential bypass should be used, but now that the old timers are gone there are very few that pipe a system correctly.



    I prefer zoning by valves, but its fine to use circs as long as the zone has correct flow. This is where I like to use the Alpha or VDT or Bumblebee circs in retrofit applications with ODR. Lots of zone control.

    I like the taco entry ZV's, my opinion but I feel the head is all that will ever need maintenance , versus flapper or ball lever style. No rubber to fail. JMO.