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Taco 404 EXP.

Hello, I have a Navien NCB 240 and have recently hooked up a Taco ZCV-404-EXP, my problem is my sentry zone valves only work if I only use the first two wires 1-2 and then jumper the 3-4 at the zone control, when I connect 4 wires , after the zone valve opens everything shuts down, then the valve closes. are these sentry valves not 4 wire? Also when I switch the dip to post purge operation on it's supposed to keep the zone output energized for two minutes after there is no call for heat, but not operate the boiler,...in my case the boiler is still running for the two minutes....I hooked everything up according to the manual,....is it as simple as reversing the TT conections?


  • Ironman
    Ironman Member Posts: 7,376
    How about posting some pics?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Zman
    Zman Member Posts: 7,569
    I think you probably have one or more of the dip switches in the wrong position. I picture of the switches would help.
    The Taco guys frequent this site often to help folks out. @Joe Mattiello is one...
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,003
    edited February 2020
    That's very strange since the end switch is the same as a jumper.

    I'd be calling Taco in the morning [(401) 942-8000] if none of us can help you out. They are very helpful.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab