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air lock? if so, how to unlock?

hr Member Posts: 6,106
it helps to purge with a bit more water pressure. either raise the fill valve to 20 psi or so, stay below the 30 psi relief valve setting.

And be sure to lower the pressure back down after purging.

You can also use a garden hose connected to a water bib, but you need to watch the pressure carefully.

Purge one zone, using those three valves, at a time starting with the highest, or longest loop.

If you purge and purge, and don't get any air, it's not an air problem :)

hot rod

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  • R. Kalia_6
    R. Kalia_6 Member Posts: 28

    I took out some baseboard and put a Runtal panel rad in its place. It fills with water (water comes out the bleed valve), but circulating (hot) water doesn't get to it at all. The relevant pipe is cold all the way to the boiler, even though there is hot water in the primary (and yes, the circulator is working). I closed off all the other loops run by the circulator, so the circ is just running this one loop, but still no flow.

    I'm an amateur but I did some homework and the head required by the panel rad is well within the circulator's curve.
    I don't have any experience here...is it possible to have an airlock such that the radiator fills with water but there is no flow (i.e. not complete blockage, but head required for flow is too high)? Is this common or unlikely? Is it something else?

    If it's an air lock, what should I do?

    The system pressure is 18psi (2.5 story house) but this loop is on the first floor. The circulator is a Grundfos 15-58 that I have set at the highest speed, without any effect (at this speed it should develop up to 19 feet of head).
  • ScottMP
    ScottMP Member Posts: 5,884

    When you say "just this loop " , do you mean it is off a scoop tee system ot monoflow tee ?

    How did you shut off the other "loops" ?

    It is possible to have a air bubble stuck some where. Runtals have small passage ways and it would'nt take much to stop flow.

    My guy feeling is you have a problem with the piping.

    Have you purged the zone from the boiler ? Try shutting off the return and opening the draw-off right above it. See is you get air. Make sure to watch your system preasure and that the boiler feed brings the system back to working preasure.

    If that dosn't work, take some picuters or tell us more about how its piped. Theres more to this than just cutting out some baseboard and sticking a runtal in there.


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  • lchmb
    lchmb Member Posts: 2,997
    another note

    One other thing while using runtal is location. If this is piped in series with regular baseboard, the runtal will serve you best on the end of the run or closest to the boiler. If it is in the middle of the loop it is recommended to use a monoflow system to feed it. I would try purging the loop as Scott mentioned, and go from there..
  • R. Kalia_6
    R. Kalia_6 Member Posts: 28

    I may not be using the right language. The zone has a pump and then the pipes branch into three, each with a shutoff valve on the return side just before the pipes merge back into one. So there are three parallel loops driven by this pump. When I have them all open, the other two loops get heat. I closed those two loops off with the shutoff valves, but still no heat in the loop of interest.

    I don't appear to have a "drawoff right above the shutoff on the return". I can bleed the radiator, or I can drain the system using the valve at the lowest point of the piping, in the primary (boiler) loop.

    What would be a "problem with piping"? The Runtal in the same place as the baseboard was. I'm not too bad at copper soldering, I don't have any obvious leaks and I don't think I soldered the pipe closed.

    Many thanks for any help!
  • Dale
    Dale Member Posts: 1,317
    Shutoff valve?

    The 3 shutoff valves you mentioned at the end of the 3 branches may be old balancing valves. The purpose of the balancing valve was to get the flow in each branch close to the same so the return temp in each branch would be close and thus heat output. I think what you may have done is add a large restriction with the panel rad. I would make the system heat,then mark the current position of each valve, make sure the valve on the trouble branch is full open, and partially close the other branches, if this works you will feel heat on the problem branch and then adjust the other 2 to get them close to the same. Be aware that if the valves are ball valves 20% open is close to full flow.
  • Chuckles_3
    Chuckles_3 Member Posts: 110

    That is why I completely shut off the other two brnaches, but still no flow in the Runtal branch.
  • John H
    John H Member Posts: 14

    Treat each rad loop like a radiant zone.Install a drain on the return side and purge the lines to the rad like a floor heat loop.I bet you get air! Make sure you install the drain upstream of the shutoff valve.
  • R. Kalia_6
    R. Kalia_6 Member Posts: 28

    Thanks! Hod Rod's advice gave me some ideas. I bled a lot of water from the radiator; I also closed off the supply and then drained at the return to reduce the pressure and then opened the supply suddenly a few times: this sudden rush of water may have blasted away the bubble or other obstruction. In any case, it works nicely now.
  • ScottMP
    ScottMP Member Posts: 5,884

    send your address so we can send the bill :)

    Glad it worked


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