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Zone valve malfunctioning looking for the cause..

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by mpilihp, Dec 23, 2009.

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  1. mpilihp

    mpilihp Feeling the Heat

    Joined:
    Apr 22, 2008
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    369
    Loc:
    Coastal ME
    Hello all, this is our second winter heating our house and dhw with a conventional wood boiler and loving it. But this winter I have an intermittent problem that concerns me about leaving for an extended time. Several times I have gone to add wood and found it over temping and the over temp aqustat activated. But my dump zone is my first floor zone and looking into it each time I find the zone valve for that zone not open. Power is applied to it but its closed. If I remove power to it and re-apply the power it opens. The zone valves I used are Taco motorized EBV valves, normally closed. I selected them because they did not use a spring to close the valve but instead a charged capacitor that when power is removed it uses that power to run the motor to close it. Also when the valve is in the OPEN state the current draw is low, the valve is not spring loaded and does not take any current draw to keep the valve open...

    I use standard relays to control the pumps and zone valves. each valve is fused separately from the 24vAC supply. This is my control setup.
    http://www.hearth.com/econtent/index.php/forums/viewthread/38912/

    But three times in the past month it has failed to open. Im afraid to leave for an extended time and have the house not be heated because of a stuck zone valve.

    Any thoughts / suggestions?

    Thanks

    ~ Phil

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  2. ohbie1

    ohbie1 Member

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    WESTERN NJ
    First thought on diagnostics:

    Have you exchanged the malfunctioning valve's operator with one that is functioning properly? This would rule out a malfunctioning actuator, and you can look elsewhere.
  3. Gooserider

    Gooserider Mod Emeritus

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    Northeastern MA (near Lowell)
    A few things you've said about the basic situation are a bit of a concern IMHO...

    1. A dump zone should be an "emergency only" item that only gets used as a heat dump on VERY rare and unusual occasions - like power or equipment failures, not as a part of normal operations - What are you doing to be making the boiler go into an overtemp situation that needs the dump zone that often?

    2. You mention applying power to actuate the dump valve - The normal recommendation is to have dump valves be "normally open" configuration, so that they open when power is REMOVED - this is the power failure failsafe, to ensure that the dump opens if there is no power to circulate the water, etc.

    That said, I agree with ohbie1, that it would be a good idea to swap the actuator for a "known good" unit to see if that solves the problem - but possibly not as my first step...

    My first step would be to make sure that whatever signal is supposed to be getting to the valve really is... If that is OK, then I'd do the actuator swap, and / or talk to Taco tech support - it would sound to me like the actuator has a leaky cap that isn't retaining it's charge properly over time - but I'm not going to put money on it, as I don't know the innards of the controller beyond the basic Taco description...

    Is this valve one that normally gets a lot of "exercise" in the day to day operation of the system? If it sits in one position for extended periods, I've heard of the valves getting sticky...

    If the valve does get used in day to day operation, is it reliable for that?

    Gooserider
  4. mpilihp

    mpilihp Feeling the Heat

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    Hi Guys thanks, I dont have a spare actuator but guess I should have one on hand so Ill get one to try it.

    As for the dump zone topic, this is a conventional wood boiler and it doesnt go into overtemp often, it wasnt in overtemp all three times just once but I discovered it wasnt heating basically because the boiler was hot and shutdown and the house was cool...

    I use the first floor heat zone as the overtemp zone (better term than dump zone since its a conventional boiler) so that I know its happening. IE house is to temp but the zone keeps running and over heats, IE Phil check it out.

    I know how a normal dump zone is configured with the normally open valve as you talk of but I didnt have the money to include one when I installed the boiler and we havent had any issues where it has over temps and dumped water out yet. My DHW also acts as a place to accept excess heat as it does not have a zone valve and system water is allowed to ghost flow through it. Im planning on adding heat to my garage and that will be my dump zone.

    Thanks

    ~ Phil
  5. Nofossil

    Nofossil Moderator Emeritus

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    If power is applied and the valve is closed, it's defective. I don't think there's any other explanation. I'd verify that there is in fact power at the valve to rule out a relay with dirty contacts before replacing the valve operator.
  6. mpilihp

    mpilihp Feeling the Heat

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    Hello Nofo yes there was power applied. at the valve it has push on connectors that you with screw connectors to secure the power leads to. So you can easily pull it off and test for power, which there was. Im going to get another power head on order, this one can sufice as a back up in the even of a full failure in teh future.

    ~ Phil
  7. ohbie1

    ohbie1 Member

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    I read this part of your post and assume you have more than one valve. If so, can't you swap actuators with another (working} valve just as a test, rather than buying another??
  8. mpilihp

    mpilihp Feeling the Heat

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    Hi yes I have another one but that is for the second floor zone and the way they plumbed it the piping goes through some crawl space and Ive had it freeze before so I dont dare have that zone potentially go unheated because of a sticky zone valve. I should have a spare anyhow so this way Ill use the flakey head as a spare to cover me when I do have one totally die in the future.

    ~ Phil
  9. in hot water

    in hot water New Member

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    Taco has had some issues with early versions of that valve. Maybe contact them with the serial number as they replaced them with updated versions at no charge.

    hr
  10. mpilihp

    mpilihp Feeling the Heat

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    Hi Hr thanks for the suggestion, in one email they said they will send me two replacement power heads GREAT!

    Thanks

    ~ Phil
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