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    Taco ZVC404-EXP Problems (15 Posts)

  • MarkTh MarkTh @ 9:31 PM
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    Taco ZVC404-EXP Problems

    My 8 Zone radiant floor heating system is controlled by 2
    Taco ZVC404-EXP Controllers.  One is the Master and the other one is the
    Slave. The system is 3 1/2 years old and has been working fine up until last
    week.  I noticed that some of the zones were not heating properly. 
    After further inspection here is what I found:

    Master:   Zone 1 is not working properly.  When Zone 1 calls for
    heat, the boiler starts, the zone valve opens, but the circulating pump does
    not run.  When zone 2, 3 or 4 call for heat, the boiler starts, the zone
    valve opens and the circulating pump starts running (they are working

    Slave:  Zones 2, 3 & 4 are not working properly.  When Zone 2, 3
    or 4 calls for heat, the boiler starts, the zone valve opens, but the circulating
    pump does not run.  Zone 1 is working properly.  When zone 1 calls
    for heat, the boiler starts, the zone valve open and the circulating pump
    starts running.

    Are both controllers bad and need to be replaced?  Thanks for your help.

  • STEVEusaPA STEVEusaPA @ 9:58 PM
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    I hope your somewhere cold. Without working thru all the wiring with a good meter, it's hard to say. My initial feeling is unless it was struck by lightening, a power surge or hit by water I'd say no. If all the wiring checks out, I'd move to checking the circ. Is your boiler also do domestic hot water?
    Is your AC t-stat tricking your heat t-stat to come on? (If you have separate stats).
    Just need a full checkout before replacing the controls.
  • MarkTh MarkTh @ 10:15 PM
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    Taco ZVC404-EXP Problems

    I am in Breckenridge, CO, +/- 10,000 ft.  So our heater runs during the summer and we do not have or need an air conditioner.  The boiler does heat our domestic hot water supply and it is working fine.  It is just strange how four of the zones will turn on the circulating pump and four of them do not.
  • Zman Zman @ 11:35 PM
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    Are you..

    Are you getting a green and red light for the open zone? Or just green?
  • MarkTh MarkTh @ 11:56 PM
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    Taco ZVC404-EXP Problems

    Both lights are turning on (Red & Yellow).  The zone valves are definitely opening.  They have indicators on top that show that they are open.  
  • Zman Zman @ 12:24 AM
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    Sounds like...

    You have a 4 wire danfos or wirsbo zone valve?
    Are there 4 wires running to the zone connection on the taco?
    The way it should work, once the t-stat calls for heat, the top light for that zone should come on. power will also be applied to either terminal 1 or 2 (can't remember,doesn't matter). This powers the zone valve motor or thermal actuator in your case. once the valve reaches a fully open position, it's switch closes terminals 3 and 4, turning on the red light and telling the circulator to turn on.
    You could double check that the zone valve end switch is providing a positive connection by putting a jumper wire connecting 3&4.
    I am thinking maybe that recent thunderstorm smoked your controllers.
    My first rule of electrical troubleshooting, when things seem really weird, double check the neutrals.
  • david sweet david sweet @ 8:56 AM
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    Votlage Surge

    Hi Mark,
    It sounds like a voltage surge caused this erratic operation, and probably due to lighting strike from a summer thunder storm. I would replace both units because they have been exposed to this surge and further problems may arise. A whole house surge suppressor may be a good investment…
    Taco has come out with a newer version of the ZVC404-EXP in the past few years. It now has a composite cover and lights in the front, time delays including priority protection as well some other enhancements. They wire similar, but the communications between zone controls are now 3 wire and not interchangeable between new and older versions. Although they can be connected together following the diagram on page 49 of the new “Taco Zone Controls Wiring Guide” #100-92. 
    Here is the link to the wiring guide on our website: [u][size=12][color=#0000ff][/color][/size][/u]
    [size=12][color=#000000] [/color][/size]
    [size=12]Thanks Again,[/size]
    [size=12]Dave Sweet[/size]
    [size=12]Taco, Inc.[/size]
    [size=12]1160 Cranston Street[/size]
    [size=12]Cranston, RI 02920[/size]
    [size=12]401-942-8000 Ex 282[/size]
    [size=12] [/size]
  • MarkTh MarkTh @ 11:37 PM
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    Zone Valve Controllers


    Thanks for the information.  I took your advice and checked the Zone Valves.  Placing a jumper wire between terminals 3 & 4 on the control panel started the circulating pump.  I also checked the voltage between terminals 3 & 4 and it was +/- 12 volts.  The voltage between terminals 1 & 2 is +/- 25 volts.  So it appears that the Valve Actuators on the zone valves must be bad.

    The Zone Valves in my system are Caleffi Z-one Z111000.  Is it common to have 4 out of 8 Zone Valves fail at one time?  Is my analysis correct?

  • Zman Zman @ 1:02 AM
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    I am not that familiar with the design of that board. The next thing I would check is the voltage of both transformers. You may need to disconnect the transformer from the board to get an accurate reading. They should both be at 24 volts or more. The reading of 12 volts is a red flag. You may just need a transformer. Maybe David from Taco will chime back in.
    This post was edited by an admin on July 17, 2013 1:09 AM.
  • bill nye bill nye @ 7:54 AM
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    terminal 3&4

    3&4 voltage? I may be wrong , but isn't this just a switch? 1+2 should power the valve open and 3+4 should just be an end switch. Even with a 3 wire Taco zone valve there may be power present at 2+3 but it is really just a switch.
  • Zman Zman @ 8:15 AM
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    The zone valve contains the switch. 3 and 4 are a circuit waiting to be completed, once you complete the circuit with the zone valve switch, the power supply (transformer) energizes the relay (load) which then closes the contacts to the circulator. There must be power there for it to work. He has a total of 4 transformers. I have no idea how they are intermingled on the board circuits.They may be isolated or they may be combined. Personally, I would disconnect them and check them one at a time.
    I am thinking if one or more transformer was damaged by an electrical event, this may be causing the problem. Transformers are inexpensive compared to a new controller.
  • hot rod hot rod @ 11:17 AM
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    that Caleffi ZV

    has a sealed reed switch as the end switch. The valve ships with a resistor that needs to be wired to the switch to protect against high surge loads.

    Some relay controls, boiler control boards and after market radiant controls modules may draw enough current to damage that switch. Here is the instructions included in the box.
  • MarkTh MarkTh @ 1:33 PM
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    No Resistors

    I checked and there are no resistors wired in the system.  Are the resistors normally wired near the valves or near the Control Panel?

  • hot rod hot rod @ 3:18 PM
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    anywhere in the circuit

    the resistor could be connected in the relay box or at the valve. probably more room in the relay box.
  • Zman Zman @ 2:57 PM
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    End switch

    Depending on the size of your circ and how it is piped you may not need the end switches at all. In your case the end switches insure the valve is open before the circ turns on. This prevents the circ from "dead heading". If it determined this is not a concern (if you have a bipass loop or a grundfos alpha circ) you could jumper terminal 3 and 4 and be done with it.
    Hot Rod,
    Thanks for the info on the valve. I did not know that.
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