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Cold zone in hydronic system

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rkwms
rkwms Member Posts: 5
in THE MAIN WALL
My hot water system has one of three zones that is cold. The others are fine. I have no places to bleed the lines at the baseboards. New boiler three years ago with new valves, but no changes to the copper piping. What steps should i try to fix this problem? thanks

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  • JStar
    JStar Member Posts: 2,752
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    What floor is the cold zone on? Do you have zone valves?
  • rkwms
    rkwms Member Posts: 5
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    rkwms

    in the middle zone on a tri-level, yes each zone has a shutoff valve. The copper pipe remains hot about twelve inches above the valve. Thanks
  • JStar
    JStar Member Posts: 2,752
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    Do you have access to all of the piping in the basement? Is there the possibility of a hidden zone valve somewhere?
  • rkwms
    rkwms Member Posts: 5
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    rkwms

    All piping except in the crawl space are available , have turned valve few times, the pipe is now hot into the crawl space, about ten feet. but none of the baseboards are warm. the other zones(, the basement floor, and the upper level are working fine.)
  • Brad White
    Brad White Member Posts: 2,398
    edited October 2010
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    Sounds like

    air binding to me. If this circuit can be isolated as you say, and drain valves at each end, it should be purged. This means forcing water in under pressure and some velocity to carry air out from one end to the other, until the water runs clear.  If there are high-point vents though, this obviously would be easier, just to vent the air out.



    I will ask a more global question though: Where does the expansion tank connect to the system, relative to the circulator? It should be as close to the inlet side of the circulator as possible and never on the discharge side, even when pumping through the boiler as is commonly done.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • billtwocase
    billtwocase Member Posts: 2,385
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    maybe air bound, or

    bad zone valve head/ or thermostat. What kind of zone valves do you have? Thermostats? Mercury switch type?
  • rkwms
    rkwms Member Posts: 5
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    rkwms

    I was hoping it was related to air in lines. As best as i can determine there are no places to drain each zone, they have valves to adjust volume of water. A new boiler was installed and they added valves as shown on the second attached. Hoping that bleeding the top most valve was the cure, but didnt want to plunge in without advice such as closing out other zones and keeping supply line open.
  • rkwms
    rkwms Member Posts: 5
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    rkwms

    Sorry second attachment
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