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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

Comments

  • Paul48
    Paul48 Member Posts: 4,470
    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 Member Posts: 6
    Problem Solved

    The aux switches in the zone valves were bad.  I replaced the bad zone valves and now everything works perfectly.
  • Zman
    Zman Member Posts: 6,991
    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
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
This discussion has been closed.