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Zone Valve Thermostat Relay

Dan_AlecND Member Posts: 2
Have a Weil McLain (CG-4-SPDN) gas fired boiler; hydronic heating for a two story house. Has two 2-wire thermostats - one zone upstairs - one zone downstairs. Just replaced both zone valves with Zone Sentry Z100C2-1 valves. Need to figure out how to wire and what relay is needed so that zones operate together and independently. We've been told that the Honeywell R8222D1014 24v DPDT (w 24v ac coil) will do the job, but need wiring diagram. I believe there are two wires coming out of the relay for 24v, and one more wire that controls the circulator pump, all of which are on the boiler side of the connection. Can anyone help?


  • newagedawn
    newagedawn Member Posts: 586
    what zone vlaves where there before?
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
    HVACNUT Member Posts: 5,452
    edited August 2017
    Can it be done? Yes.
    Will it be pretty? No. You'll have a mess of exposed low volt wiring on the side of the boiler. The switching of the relay might be loud mounted to the metal jacket of the boiler.
    And you would need 2 relays, 1 for each zone.
    Your best solution, one that Taco has for your exact situation is the ZVC403 zone valve control.
    If you feel confident to wire seperate relays, then you should be able to tackle the ZVC403.
    If not, you can post back here, and we'll be happy to help with wiring.
    You should post some pics so we have an idea of what's existing.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,520

    Good practice .Use an separate 24v transformer 40VA will be fine , fuse it with 3amp fuse or go up to an 50VA that comes with an circuit breaker to power zone valves . Dont use the burner transformer ... The end switches will connect in parrell , to the two black control wires on left side of boiler , check the wiring diagram on boiler .. They will show an thermostat between the two wires ..
    I have enough experience to know , that I dont know it all
  • Dan_AlecND
    Dan_AlecND Member Posts: 2

    Images have been posted, and assume that it needs to go through a review process before being view-able. We also posted a .pdf that shows how to wire with a DPDT w/24v coil (R8222D1014). This is our preferred method if it will work. If not, we're also reviewing the possibility of the recommended TACO ZVC403 4 Zone Valve Control. Do you know if it will work on our system, and can you supply the wiring information for this controller.

    The zone valve installed replaced the old TACO ESP's.

    Thanks in advance.
  • NY_Rob
    NY_Rob Member Posts: 1,370
    edited August 2017
    Why do you want to use a relay in the circuit?
    The T-Stats will control the zone valves directly and the zone valves will fire the boiler.

    Big Ed's diagram will work as is without a relay.

    Here's my homemade version of the same diagram for use with the Zone Sentry zone valves...

  • Jim216
    Jim216 Member Posts: 2
    Is it possible to operate one Taco Zone Sentry 4-wire through a SR503 Switching Relay (instead of a ZVC)? I currently have both floors of my house operating on one thermostat, through a SR503 and single 007e, and a 40-gallon water heater. I'd like to install the Sentry ZV on the second floor loop, but arrange it so that when the upstairs thermostat calls for heat, both zones are heated (the first floor zone will always be open). This is a radiant heating system in a tiny house, 700 square feet.

  • SteveSan
    SteveSan Member Posts: 211
    Hi Jim, I believe you emailed Taco yesterday and I replied back to you with a wiring diagram how to wire in a Taco Zone Sentry Valve to your SR control. Please see the attach wiring diagram. If you have any questions please call into Taco Tech Support @ 401-942-8000 Mon-Fri 8am-5pm EST, ask the operator for Tech Support.
    ZmanErin Holohan HaskellJim216
  • HomerJSmith
    HomerJSmith Member Posts: 2,309
    It seems to me that if you have 2 thermostats and 2 zone valves, it would always operate independently. What I think you mean is that they operate in the same time frame when both thermostats are calling for heat.

    If so, there is no need for a relay, just a transformer to provide power to the thermostats, which sends that power to the zone valves.

    Ed's diagram is the one to follow. It's simple.
  • Jim216
    Jim216 Member Posts: 2
    The rumors are true...Taco customer service is fantastic! Thanks Steve and all, this was very helpful. I didn't realize it at the time, but I think my main point of confusion was whether or not I needed an auxiliary 24v transformer (rather than somehow using the SR503's 24v tap). This should be a pretty straightforward job now.....thanks again!
  • hot_rod
    hot_rod Member Posts: 20,725
    The transformers in some pump relay boxes are not very large, 20 Va or smaller?
    Be sure you have enough Va when you start using 24V from the box.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SteveSan
    SteveSan Member Posts: 211
    You're welcome Jim, please feel free to give us a call anytime during normal business hours for any assistance you may need.
    Erin Holohan Haskell
  • HomerJSmith
    HomerJSmith Member Posts: 2,309
    edited December 2020
    The great thing about Taco Sentry zone valves is that the 24 V don't operate the valve. The 24 V charge a capacitor and the charge in the capacitor operates the valve motor. If the 24 V are not optimal it would take longer to charge. However, the current draw must be lower than the rating of the transformer or the fuse wire in the center tap of a Class 2 transformer would blow rendering the transformer useless.

    It is possible to gang 2 transformers together for added current draw, however it is just better to use a separate higher current transformer for the zone valves, if needed.

    I believe that the Taco relay box has a 40VA transformer and that would be adequate.