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Taco ZVC 403

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We saw a job yesterday that had 15 Caleffi manifold actuators on a zone valve controller that had a 40 VA transformer. Each actuator draws 3 watts x 15 actuators = 45 VA. With all the zones on, the transformer is very hot. What's the best way to get a properly sized transformer installed?
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

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  • ChasMan
    ChasMan Member Posts: 462
    edited December 2017
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    Transformer temperature rise at full load is stunning. Often 65 degrees C. That translates to very hot (149 F). The easiest thing to do is just buy a bigger one and mount it outside the box and then disconnect the one in the box. There is not a lot of room in the box for a larger transformer You can fit a second one in if you move the one that is in it up a bit but that's a pain since you would have to phase them correctly yourself. And the little Mini Fit Jr connector is rated at 9 amps so it should be ok. I would just externalize it. Or, you could buy a Caleffi box which can take two transformers even in the three zone box. Or buy a six zone box from Either Mfg since they already have two transformers. The Caleffi one has non defeatable pump exercise which doesn't open the zone valves ugh... Grundfoss has the nicest box feature wise but it is rare and they are quite proud of them.
  • hot_rod
    hot_rod Member Posts: 22,256
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    So here is a graph that shows 3 of the different Caleffi zone valve current draw.

    With the thermal actuators that full current draw is only for a few seconds. As the wax cartridge warms up, the current draw continues to drop off, ending up under .2.

    So unless all the actuators happen to get a call from a cold start, or they are all on one zone :) it would be rare to see a constant 45vA draw.

    One instance when it could happen is after a power outage where they could all be firing at the exact same second. But it is prudent to size for the entire load.

    Note also that we now have low current draw actuators in the standard and TwisTop, 250 mA per actuator, which is not on this graph.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Alan (California Radiant) Forbes
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    Thanks ChasMan; I didn't know that Grundfos made zone valve controllers.
    HR: Great info. on that graph. Thanks!
    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
  • GW
    GW Member Posts: 4,701
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    how many heads on the largest zone? whatever the answer is, lets say '3' for example sake. Can you simply set up a separate trans and a spst relay and make the 'largest' zone (most number of heads) work through its own trans?
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com
  • ChasMan
    ChasMan Member Posts: 462
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    Relay idea is good if there is no priority call on the controller. If there is no priority then no need for a zone valve controller at all in my opinion unless you want pretty lights.
  • GW
    GW Member Posts: 4,701
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    Ahh yes if there’s a priority then a DPDT is needed, it gets to be a bit much
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    gary@wilsonph.com