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    Taco ZVC404-EXP Problems (4 Posts)

  • Summit Summit @ 7:30 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 properly).

    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.

    Mark
  • Paul48 Paul48 @ 9:39 AM
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    zone valves

    I'd jump the end switch of on of the zones in question and see if that starts the circ. I suspect end switches are the problem and not the ZVC's.
  • MarkTh MarkTh @ 7:57 PM
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    Problem Solved

    The aux switches in the zone valves were bad.  I replaced the bad zone valves and now everything works perfectly.
  • Zman Zman @ 10:37 AM
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    HR

    Mark,
    Did you see Hot Rod's note on your other post. If you don't have resistors on the zone valves you will keep burning out end switches. He is the Calliffi trainer.
    I would also evaluate whether you need the end switches at all.
    Carl
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