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Zone valves and RIB cubes

Hi all,

I am troubleshooting a hydronic system zoned with Taco ZVs ocupled with RIB cube relays. Its the first time I have seen such an arrangement, and I"m having trouble figuring out the control logic. Is  anyone out there familiar w3it5h this arrangement? I could use some guidance.

Thanks, John S.


  • icesailor
    icesailor Member Posts: 7,265
    Smart Relays:

    Someone who thinks they are a lot smarter than many of us was trying to save $50.00 when they were loosing $150 on the job and went with the RIB relays.

    Do yourself a favor. Don't cloud your brain with trying to figure out how to make the Ribs work. Rip them all out and put in a Taco ZVC404 zone valve relay control. Re-wire the mess to work, and be glad that you didn't do it.

    ZVC Relays were designed for electricians that don't understand control wiring and will never learn.
  • J. R. Sullivan H&P
    Zone valves and RIB cubes

    I appreciate the sentiment, but replacement isn't a practical option - big building - I have to live with what I'm looking at. Trouble is I don't have an understanding of what I'm looking at.

    John S.
  • icesailor
    icesailor Member Posts: 7,265

    Are you dealing with Taco 57* Wax Motor Valves buried around on multiple floors?

    If you are dealing with Taco 500 series wax motor zone valves, I can't imagine a place where you need RIB relays. Everything you need is already in the valve. Are the valves supposed to operate fan coil motor fans?
  • J. R. Sullivan H&P
    Zone valves and RIB cubes

    Hi Ice,

    The zone valves are Tacos with the conventional three wire gold power head. The valves are controlling flow thru fin tube elements (piped in parallel) to provide room by room zoning. I don't "get" the presence of the cubes, but there they are wired to each zone valve. I don't understand where they fit in between the transformer,thermostat, and zone valve.


    John S.
  • Zman
    Zman Member Posts: 7,574

    I am guessing here but it is likely that the RIB is being used to isolate the 3 wire zone valves from a boiler that does not play nicely with them.

    Which RIB do you have? How is it wired?

    I think RIB makes some really useful and versatile products. Most of the ones you see in heating systems are just DPDT relays in a handy enclosure.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Steamhead
    Steamhead Member Posts: 16,889
    I think you're right

    if the coil of the RIB is wired to terminal 3 of a Taco 570-series or other 3-terminal ZV, it is being used as an "isolation relay".

    The terminals on the 570 ZV head are:

    1- to thermostat

    2- 24V power feed, usually coming from the R side of the transformer

    3- end switch sending 24V out to a relay or other equipment.

    Terminal 2 is wired internally to one side of the heat motor and also the end switch. The thermostat is wired to the other side of the heat motor via terminal 1. When the thermostat closes, it completes the circuit thru the heat motor back to the C side of the transformer, and the motor expands the wax to open the valve.

    When the valve opens, it closes an internal switch (the "end switch") and 24 volts appears on terminal 3, goes to a relay coil which activates the relay, and back to the C side of the transformer.

    It is possible to wire these ZV heads to the TT terminals of the usual boiler control without using a relay if you get the polarities of the transformers just right. But I always use a relay because sometimes transformers don't play well together, and it's way too easy to get polarities mixed up on a 1:30 AM no-heat call.

    The ZV relay panel Icy mentioned does basically the same thing, enclosing all the hook-up wiring in the housing so you don't really have to think about it.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • icesailor
    icesailor Member Posts: 7,265
    edited August 2014
    Taco ZVC Controllers:

    They also give an element of isolation from the valves to the boiler. Because few Sparky's understand boiler control wiring, I always explained as best I could how to wire it and let them have at it. Then, if it didn't work, I rewired it so it did.

    As far as the RIB Ice Cube relays on Taco wax motor power heads, you need constant power to the RIB relays. And if somehow, Sparky ended up wiring XC/ZR into the transformer etc, all kinds of wonderful things can happen.

    Where do you get constant power for the Relay? #1 and #2 are switched through the thermostat. # 2 is common to the transformer. When the call comes from the thermostat, #1 and #2 make and tell the was motor coil to heat up and blow the valve actuator plunger through the bottom of the valve. On the way down, the plunger makes contact with a micro switch which closes the TT side of the control. As it gets to the bottom of the travel, and before it gets to blowing its way out the bottom, the plunger pushes on another closed micro switch and opens the power to the wax motor coil. After cooling, it will make again and cycle. The polarity issues arise when you have more than 3 valves on a 40 VA transformer. And #2 is common to any and all transformers in the circuits. If you have 4 valves, you can use a 60 VA transformer. Or if you have more than three, you can use two 40 VA transformers on 6 valves. Then, you need to worry about polarity. Which may not be obvious ever. And then, there's that 24 volts in the boiler control polarity. And if you use ZC/ZR, all power is killed to anything wired through the ZC/ZR. Like thermostats.

    ZVC relays resolve all this. Anyone not using ZVR controls must enjoy mental anguish. I can't imagine trying to troubleshoot a bad valve head with RIB ice cube relays. Sparky's using Rib Relays must be like Tool Weenies. They have to buy and try out the latest great invention. Until the next new offering.

    A nice trick with those powerheads. The manual levers are always hard to push down, even when new and just out of the box. Give then a spray with WD-40 or your favorite spray lubricant, and operate the lever a few times. Once done, the lever will operate like a cold knife through warm butter. If you get sticky powerheads, the valve plunger sticks in the bore on the hold down plate. Take the head off (after disconnecting the power for 3 minutes) and spray with Kroil. Take a large pair of water pumps and squeeze it down and up until it moves freely. Goop it with Never-Seize. You are good to go. If the valve body parts are leaking and stuck, and you need to replace the plunger assembly, you can replace the whole valve by draining, replacing and re-filling the system. Or pull a vacuum and take the large water pump pliers, put one end on the bottom, the other end on the top, hold the plunger down to overcome the spring, and remove the screws holding worn the plate. Loosen them up first so you know they will come out. Take a brand new complete valve and take the plunger assembly out like above. Grease the O-Rings with Silicone Grease and put it back in, holding it down with the water pump pliers. Put the plate and screws back. It is a one man job. A least it was for me. I never had a helper. Save the power head for a new replacement. Throw the brass valve body in the brass scrap barrel. The cost of the separate parts is far more costly than an entire new valve. No one stocks the repair parts but they all stock the valves. The valves are the same since 1970's or earlier. That's how long I have been doing that.
  • Don_197
    Don_197 Member Posts: 184

    Hi there,

    Since you said "Large Building" it occurred to me that there may be a building automation system here that isn't being discussed. Controls Contractors use RIBs for EVERYTHING. It could even be posiible that the main controller puts out 24volts DC and they had to install the relays to activate the zones. What do you think? What is the model number of the RIB? is it a RIBU1C?

  • icesailor
    icesailor Member Posts: 7,265

    Like I said. Sparky just had to turn a small project into a circus. Because they don't know how to wire small control situations. Some don't have the sense that God gave a goose. And that's not a lot.

    I did a job with 3 Taco 572 zone valves and left a ZVC 404 controller there, When I got back, the ZVC 404 was still in the box and there were ice cube relays and transformers plastered all over the floor/ceiling and wall in a 200+ year old house. Good thing the owner was hard of hearing. The hum from all those transformers etc was awful.

    And it could have been so easy.