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Taco ZVC controls...

I am not an electrician but I have wired a lot of boilers.
One thing I have noticed on the taco zvc relays they want you to run all the low voltage in the top and all the high voltage in the bottom. If they are all in the same box and you are not overlapping the wires what is the "issue"...


  • Empire_2
    Empire_2 Member Posts: 2,343
    edited September 2015
    No I'm pretty sure the lo voltage enters through the top and line into the bottom...
  • kcopp
    kcopp Member Posts: 4,188
    So why cant you use just one of the hole (say to the top left) through to feed the unit w power 120v and the others up top for the low voltage...?
  • SWEI
    SWEI Member Posts: 7,356
    Not quite sure exactly what you're describing, but if it's mixing line voltage and low (controls) voltage wiring in the same J-box, it requires that all the low voltage cables be rated for 300V (generally a CL3 rating.) Thermostat wire is not so rated, which is why many prepackaged controls have a way to segregate the two (Tekmar comes to mind.)
  • hot_rod
    hot_rod Member Posts: 19,262
    What we learned from our UL inspector regarding the wiring inside the Caleffi relay boxes. If there is an actually connection point or terminal for every wire to "land" on then there is no need to have a separation between the various voltages

    If the wiring required connections like wire nuts inside the enclosure the you need a separation.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SWEI
    SWEI Member Posts: 7,356
    Right -- as a listed device, it is covered.

    In the field, we can't mix them in boxes or raceways unless the jackets are properly rated.
  • Joe Mattiello
    Joe Mattiello Member Posts: 663
    I know Taco controls are United Laboratories listed but I couldn’t intelligently explain the criteria for conformance, so I asked one of the product engineers to help me out.

    UL, as well as NEC, require low voltage wiring separated from line voltage wiring and uninsulated components separated by a barrier and/or by routing. For ZVC controls, UL required Taco to use a barrier to separate and identify high and low voltage wiring compartments to prevent the conductors from touching high voltage components on the circuit board. The ZVC, 120 v power input and 120v pump wiring should be fed through the 120V labeled knockouts located at the bottom left. Thermostat wiring is fed through the top, and zone valve wiring is fed through knockouts on bottom right.

    The issue with running different circuits next to each other, is wiring could touch with normal slack left in the box, to minimize that, best practice is to keep the circuits as far apart as practical. This helps prevent contact not only at time of installation, but also for future additions to the control. Regarding using a top hole for the power, Taco boxes are not set up that. It’s allowable with best practice for the installer to pop a new conduit hole on the top, and left of barrier.

    Further, our controls are listed against UL standard 873. Section 35 of the standard lists requirements for separation of circuits. Specifically, section 35.2 talks about separation requirements for field installed conductors. The basic requirement is conductors must be separated by barriers or adequately segregated. Adequate segregation requires conductors to be clamped or routed to provide a permanent separation of at least ¼”. For zone controls, this basically refers to keeping the 24V conductors away from, line voltage conductors, and line voltage circuit board components. The standard also requires that when evaluating adequate separation, 6”-12” of slack must be considered for each conductor. This makes ensuring segregation difficult when the entry points for different circuits are right next to each other.
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
    Steve Thompson (Taco)kcopp
  • kcopp
    kcopp Member Posts: 4,188
    Well there you have it... now I know. ty much. kcopp