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Circuit Setters and 2 Manifolds to Single Zone Valve

tdfontaine Member Posts: 5
edited October 2021 in Thermostats and Controls
I would like to get some advice from the experts about circuit setters and tees after a zone valve (2 manifolds to a single zone valve). The system is new construction in-floor hydronic (combination of gypcrete on the first/second floor and concrete slab in the basement and garage) and has a full manual J so I know the design flow for each manifold and loop. The boiler is a HTP EFTU which will use a 2 pipe 20 gallon buffer tank to prevent short cycling of the smaller zones.

Zone 1 – 2 manifolds (6 loops on manifold 1 and 10 loops on manifold 2)
Zone 2 – 2 manifolds (5 loops on manifold 3 and 8 loops on manifold 4)
Zone 3 – 1 manifold with 5 loops
Zone 4 – 1 manifold with 2 loops
Zone 5 – 1 manifold with 4 loops

All the manifolds are Caleffi twist flow so the loop flow can be adjusted for each loop. Perfect scenario is to use circuit setters for each manifold but that adds cost that I’m not sure is required since each loop can be adjusted with the twist flow manifold.

For zones 1 and 2, what is the best practice for connecting two manifolds to a single zone? Does each manifold need a separate zone valve or can one zone valve be tee-d to two manifolds?

Appreciate the help!


  • Jamie Hall
    Jamie Hall Member Posts: 22,077
    If both manifolds are to be controlled by the same controller -- thermostat or whatever -- you only need one zone valve.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • tdfontaine
    tdfontaine Member Posts: 5

    If both manifolds are to be controlled by the same controller -- thermostat or whatever -- you only need one zone valve.

    Thanks Jamie.
  • HomerJSmith
    HomerJSmith Member Posts: 2,307
    edited October 2021
    How are you moving water to the Twistflows? Circulators or zone valves? I assume zone valves from your post.

    Twistflow adjustment are to balance the loop on the manifold. They are not for balancing the various circuits to the manifolds.

    If you are using zone valves and a single pump, make sure it is a variable speed ECM pump.

    Whether you need a 20 gal buffer tank or not is dependent on the sys. Caleffi Idronic series on line has an issue about sizing buffer tanks, as I recall. It has the math.

    Another thing to consider is whether you need different temps in different loops.

    I don't use circuit setter valves, I use other manufacturers. One needs a differential pressure gauge to set the flow. Caleffi Quick Setter doesn't, you can just read the flow off the valve.

    Circuit Setter valves are used to balance the different circuits to the various manifolds.
    I use them with the twistflow to do just that. They are used to balance the resistive load of each circuit so that the flow to the manifolds are the same, regardless of how many loops are on a manifold.
  • Zman
    Zman Member Posts: 7,493
    You shouldn't need additional balancing.
    In my experience, if your loop lengths are within 10% of each other and you design distribution piping to remote manifolds generously, radiant systems pretty much balance themselves. If you do need balancing, the manifold balancers should take care of it.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tdfontaine
    tdfontaine Member Posts: 5
    Zman - thanks for the input. I'm going to install w/o the circuit setters and see how things go. If I'm having problems then I can always add the circuit setters at a later date.