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Zone valve / controller trouble

MTMikeMTMike Member Posts: 2
Background: I've got a 4 zone system, with a Taco ZVC405-4 controller, old Honeywell "gold" valves, and Honeywell RTH2300B thermostats. Over Thanksgiving, the basement valve motor stopped opening all the way: it would open the valve but not hit the relay. The motor was extremely hot. I replaced the motor and everything was worked again.

Problem: Last night, I noticed the house was cold- I went downstairs and 3 of the 4 zones were doing the same thing. The valves were open, but none of the motors had gone far enough to hit the relay. All three motors were hot. The basement (with the new motor) was one of the zones! This morning, only the basement valve is acting up. The other two zones appear to be working correctly.

Any idea what's going on here?


  • Jamie HallJamie Hall Member Posts: 12,701
    Check all the voltages?
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • MTMikeMTMike Member Posts: 2
    I'm really bad with multimeters, but this is what I think I'm seeing:
    measuring across TH and TR:
    zone off: 0v
    thermostat calling, motor opening: 3-4v
    thermostat calling, motor all the way open: 18-26v

    (with 3 zones all the way open: 30v at each???)

    Unfortunately for my testing, the valves are all working fine right now.
  • unclejohnunclejohn Member Posts: 1,525
    edited December 2015
    Not sure what a "Gold" valve is but I would replace the other three valve motors. The Honeywell zone valves I see are .23 amp draw. so with all zones calling maybe 1.0 amp at transformer. The amp draw of your valves should be marked on them.
  • hot_rodhot_rod Member Posts: 13,188
    The current draw of those valves is 1.2A so 1.2 x 24V= 28.8 VA each.
    Plus whatever small current the t-stat might draw, if it is a power stealing type stat.

    So 4 valves would be more current draw than what a common 40VA transformer would carry. What size transformer are you powering it with?

    The problem generally shows up when all the valves call on at the exact same time. You can saturate the transformer to a certain degree, but you may be under powered. Read the voltage when all 4 valves first kick on, at the same time.

    Did you change stats, or the relay box recently? Or maybe the transformer is just giving up from over current conditions.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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