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Taco Zone Valve

Time for Taco to make the powerhead with dry contacts and make just about everthing easier to wire the zone valves

Comments

  • DaveS
    DaveS Member Posts: 3
    Zone Valve Heads Keep Frying

    A friend had a tech replace some fried Taco 570 heads. Tech left, system fired up, another head burned up.
    I checked wiring. All per Taco schematic label on head.
    Ssytem is n.g. fired boiler. 3 zones. One circ pump. Honeywell L8148E aquastat. Did have T87 stats. Now Lux 5+2. Failures under T-87's and Lux.
    Apparently system has been doing this for years. Get this - one of the 570's DOES NOT burn up. Only the "outer two" on the schematic (not that it should matter). Xfrmr volts OK at 28V-no load. Volts/amps at 24/0.9 across pins 1-2 during actuation.
    Replaced a head today, triple checked wiring, fired up system. Another dead head. "Middle" head on system - no problems. Works fine.
    Failure mode appears to be caused by resistor element in head wax cylinder is WAY overheating, overexpanding (pressure) and rupturing cylinder.
    How could only two of three heads overheat/fail? (Heater Ohm check squares with mfr specs)

    Is the L8148 a correct match for these valves?

    What gives?

    Thanks,
    Dave
  • heatboy
    heatboy Member Posts: 1,468
    If you are trying.....

    ..... to power the valves directly from the aquastat, that is your issue. Internal transformer is not powerful enough for Taco valves. You will need a minimum 40 VA external transformer to power them.

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  • DaveS
    DaveS Member Posts: 3
    If you are trying.....

    Got the 40VA 24V ext xfrmr. Checks out at 28V no load. All three valves show that it supplies 24V to pin 1 when stat calls for heat.
  • Chris_82
    Chris_82 Member Posts: 321


    Try the resistors...
  • Darrell
    Darrell Member Posts: 303
    Polarity matters

    Polarity matters...when you are mixing two different transformers as you are doing. When your Power Heads go fully open they "mix" elecricity from both transformers, (the external 40va and the onboard control transformer), across the #2 terminal. The best way is to use the Taco Zone Valve Controller which isolates the on board controls from the zoning controls.

    If the same heads consistently burn out, then the problem is probably with the OTHER power head/t-stat/wiring sub-system. Look for burned and shorted wires which may test fine with a meter unless you happen to test them disconnected to ground...(the piping they are stapped to).

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  • Darrell
    Darrell Member Posts: 303


    But, then what would I do for a living? Changing all those V8043's gets boring after awhile.

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  • DaveS
    DaveS Member Posts: 3
    Polarity matters

    I will go down that road and try the zone controllers. Makes sense. Thanks much.
  • zeke
    zeke Member Posts: 223


    I would check the voltage between 1 and 2 terminals for 24VAC and make sure that the heat element power cycles on and off during the "on" operation of the Tstat. You will need a clamp-on ammeter to verify the cyclic current at the heating element. It may be that the installation is not allowing this cycling of power ( Taco allows horizontal and top mounting only)I suspect that you are getting continuous power to these failed units due to the orientation of the installation.
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