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Taco Zone Valve Wiring

mcoeks Member Posts: 13
This is how my Taco Zone Valves are currently, we bought the house with the system in place.

On the Zone Valves - 1 is red, 2 is white and 3 is blue. The red is connected to each floor stat red wire, white is connected to the 24v transformer, blues are connected together than to boiler. The white one each floor stat is connected to 24v transformer then over to the boiler.

I put an addition on my house and added two more zones, I got another transformer. On the taco box the wiring diagram is different than my system. So should I change what is working to match the box or leave it and match the new system to the old?

Thanks for the help.


    EBEBRATT-Ed Member Posts: 8,851
    You can add another transformer and more valves. It's all in the way you connect them. See the attached Taco brochure. It is a little confusing with multiple transformers
  • In the long run, you would be better off installing a zone valve control. Makes it easy to wire and easy to diagnose when there's a problem. It comes with transformer(s).

    Often wrong, never in doubt.
  • mcoeks
    mcoeks Member Posts: 13
    That brochure helps more than the back of the box. But page 3 bottom right it shows the boiler being connected to 2 and 3 off the zone valve. In my setup its off the thermostat and 3 off the zone value.

    EBEBRATT-Ed Member Posts: 8,851
    edited April 2

    Look at the diagram with the two circles that shows the valve internal wiring. It shows the thermostat, the end switch that starts the boiler the transformer connections etc. It explains how you can have multiple transformers without burning something up. You need to know that to connect all your end switches to start the boiler We can't see everything you have unless you draw it out and post it. Or you can invest in a zone panel as @Alan (California Radiant) Forbes mentioned
  • mcoeks
    mcoeks Member Posts: 13
    Here is how my wiring is, does this help?

  • hot_rod
    hot_rod Member Posts: 14,753
    You have some 3 wire and 2 wire zone valves? How many thermostats
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mcoeks
    mcoeks Member Posts: 13
    No all 3 wire zone valves with 3 zones with 3 thermostats. The thermostats are all on top and the zone valves are below.

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,091
    edited April 2
    This is where many a good transformer gets the smoke let out of them.

    Whatever you do, it must be the same on each valve. Don't try to follow a different plan on the new valves, while leaving the old plan on the old valves.

    The first thing I would do is: determine if the boiler operates without the zone valve transformer. The wiring plan you show above indicates to me that the transformer for the zone valves MAY also operate the gas valve.

    To do this,
    A. turn off power to the zone valves.
    B. Manually open all the valves
    C. disconnect the # 1 wire from each valve.
    D. Disconnect both of the wires that go to the boiler.
    E. Place a jumper wire on the wires you disconnected at the boiler
    F. Power the boiler.

    if the boiler fires and the circulator operates, then the original boiler wiring is probably correct and you can now focus on the zone valves. If the boiler does not operate, then there is a possibility that the zone valve transformer also operates the boiler controls. That would be a problem for adding additional valves with additional transformers.

    Finally, purchase some 3 amp automotive fuses and 2 automotive fuse holders. Connect the fuse holder to the R terminal of each transformer before you power them with house current. That way, if you make a mistake, you will lose a $1.00 fuse. and not a more expensive transformer.

    Let us know if the boiler operates without the zone valve transformer. After that is determined, we can go to the next step.

    I agree with Alan Forbes above, get a ZVC 6 or equal control. they make wiring easy and understandable. if there is a failure in the future, it makes it easy to diagnose if there is a wiring problem or not. I have heard of electricians spending hours on solving a no heat problem, only to find there was air in the line... The electric side was working just fine.

    Yours Truly,
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • HomerJSmith
    HomerJSmith Member Posts: 1,286
    edited April 2
    The make and model of the existing zone valves and the new added zone valve would be helpful.

    I'm assuming that you have Taco 571, three wire zone valves. If so the following link will show you how to wire the zones.

    A thing to remember is that there is a limit on how many zone valve that can be powered by a 40 VA transformer (usually three). If you add zone valves you need to have more power. You can gang transformers together, but it has to be done in a specific way with the correct polarity. It would probably be better to buy a new transformer that has the higher VA with a reset button (circuit breaker) in case you make a wiring error.

    You could power the existing zone valves with the current transformer and use another 40 Va transformer to power the new zone valves. The two ZV circuits would be independent of each other. The only connection between the ZVs would be the boiler TT transformer circuit. I think that would work. I would prefer a single aux transformer tho that would power all the ZVs.

    Study the brochure wiring diagrams so that you fully understand them. Basically, the auxiliary transformer and thermostat are connected to the #1 & #2 terminals. The boiler transformer is connected to the #2 & #3 terminals thru the TT connection on the boiler.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,091
    Homer has a good point. you can operate all the valves from the same transformer if it is powerful enough. And that makes things simple.

    If you want to use the new transformer you purchased already then you want to be careful and follow the instructions exactly.

    When teaching anyone about wiring zone valves I tell them "electric is color-blind" the colors are there for your convenience only.

    I tell them, as I have already mentioned above, the first step is to place a fuse on the R terminal of the transformer. From the other side of the fuse use the red wire to connect to the R terminal of the thermostat Grom the thermostat use tye white wire to connect W on the thermostat to #1 on the zone valve. #2 on the zone valve gets connected to the C on the transformer. (You can use whatever color is left for common. I like Black, Brown, or Blue, but if you only have a Green left, that will do fine.) This is the way Taco describes it in their diagram

    By using this consistently you will keep the Power side of the transformer isolated from the Power side of the boiler control transformer. I have a feeling that someone messed up the boiler transformer a long time ago and fixed it by using the zone valve transformer to power the gas valve. That is why you need to do the test I described above.

    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • Joe Mattiello
    Joe Mattiello Member Posts: 605
    This is a great website for help.
    the Taco 3 wire zone valve are pretty simple. 1, and 2 are thermostat wires across the two poles of transformer. 2 and 3 are your end switch that is wired to T T terminals on boiler. 
    Taco does offer a zone valve control to facilitate wiring. I recommend it highly.
    for additional support, contact Taco at 401-942-8000 and ask for tech support. 
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
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