Control two actuators as one zone?

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Greenmountain

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I'm setting up a hydronic heating system using supply and return manifolds with 5 ports each.
There are actuators for the ports on the return manifold:


Was looking at the Taco 3 zone controller (https://www.tacocomfort.com/documents/FileLibrary/102-391.pdf).


I'd like to have a total of three zones, where Z1 controls two of the actuators, Z2 controls two of the actuators, and Z3 controls 1 actuator.

In order for one zone on the controller to operate two actuators, I'm wondering if I can simply splice the wires for two actuators together to be powered by the zone controller?

Looks like the actuators have a "max inrush current" of 250mA, so a total of 0.5A per zone with two actuators wired together.
According to the specs for the controller, it says, "All thermostat and zone valve connections supply a 24VAC class 2 output", which is 1amp @ 24V, correct? So if my max draw would be 0.5 amp per zone, with max total draw of all 5 @ 1.25A.

Looks like the controller is "24VAC per Zone 40VA Total". Is 40VA @ 24V 1.66A??
 
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Fitter30

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If the actuators have end switch use the switch to slave the 2nd actuator with a external transformer. For what a transformer cost i wouldn't use the factory trans or contacts. Want some cushion between what the contact is rated and in rush.
 

jadnashua

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It should work if one zone was activated at a time, but that may not occur. Say all three zones wanted to turn on at the same time, it could overload the transformer. If the controller was a little smart, it may sequence things with a slight delay in between, and the total load should work. It may not be too hard to select a higher VA transformer. Each individual controller would not be overloaded, nor would the circuit with all of them engaged.
 

WorthFlorida

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The TACO unit is designed to operate with three different thermostats. It is a very well made unit and easy to install. Its own 24v transformer is only for its internal relays. If you try to splice in any of the actuator's with another, when any one of them gets voltage, the others will also operate. Trying to understand what you're trying to accomplish, you'll need to designed your own control board and it is not as easy as it sounds. Going with multi stage thermostats may somewhat accomplish your needs.

If you are using one thermostat, you can get a 3 stage heat/cool unit. As the temperature drops, stage 1 will operate, if the set temp is more than 2 degrees the 2nd state will operate, and colder a 3rd state will operate where all three are running at the same time. As the space warm, the 3 rd stage will turn off, 2 and finally the 1st stage. Each stage is wired to the three zones of the TACO unit. Or use two thermostats where one is a 2 stage heat and the other single stage. This may be your best solution.
 

Greenmountain

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ok, not sure I understand all these options completely... But going back to the original potential set-up...
The goal is to have three heating zones (no cooling) each controlled by a thermostat.

I know this is not really a typical set-up, but two of the three zones would have two separate heat/return circuits each controlled by an actuator, so each zone has two actuators (rather than a more normal arrangement where one zone would operate one actuator). Hope that makes sense.

It's true that all three t-stats would need to call for heat and trigger all five actuators at the same time to approach the amp limit of the controller, though if I'm understanding the electrical traits of the actuators, that "inrush current" can last up to two minutes, so increasing the likelihood of that scenario.

I guess my question is more trying to understand the amperage limits of the controller. Even in a worse case scenario, with all 5 actuators pulling max inrush current simultaneously, I believe that would still only be a total of 1.25amps, which is still below the stated max capacity of the controller, though this is the part I'm unclear about.
If the max current for the controller is 40VAC as stated, I believe that is 1.67A @ 24V. Does that sound right? (I used this calc: https://www.rapidtables.com/calc/electric/va-to-amps-calculator.html) So in theory, even in a worst case amp draw, I'd be drawing a TOTAL 1.25A with a limit of 1.67A.

The highest draw per zone would be two actuators combined, so 500mA, and the controller rating is 24 VA per zone, which at 24V would be 1A, correct? It seems that each zone is rated for 1A@24V, but the total system limit of all three zones is 1.67A.

So, is the consensus that this is too much current for the ZVC403 controller?

If so, would a more simple solution be to use the ZVC405 5-zone controller, which has two 24V transformers (double the output capacity), and then just spice the t-stats rather than the actuators (one t-stat operates two of the controller zone contacts/two actuators)?
 
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Fitter30

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For a 40 va transformer 1.67a is correct 40 divided by 24.
Not using zone valve end switchs use another transformer to power the 2 nd actuator. If your a manufacturer you can test your equipment at max whatever.
But if your doing field wiring and eat a controller it will be on you unless you have a very close relationship with the supplier.
 
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