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vacuum on air vents

bill Nelligan
bill Nelligan Member Posts: 5
in THE MAIN WALL
I have single pipe steam, boiler in basement, two of the 5 radiators on the 1st floor have vacuum on the air vents. I have replaced the vents but have the same problem, it seems to be after the boiler has gone off. these are adjustable vents and when you set them to 1 or 2 the vacuum goes away, but the radiater does not heat anymore at that setting.

Comments

  • Norm Harvey
    Norm Harvey Member Posts: 684


    What kind of vents are they?



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  • Brad White_9
    Brad White_9 Member Posts: 2,440
    Vacuum

    The vacuum is naturally formed from collapsing steam which you probably realize; if the vent is still at temperature (closed) it will not perform it's vacuum breaker function. How soon after the off-cycle does this occur? What is the corresponding radiator temperature?

    Also your dial setting- the 1 or 2 setting I gather is nearly closed ("slow" on the dial), so I am wondering how that is working? Does the vacuum release as you turn it or is it coincidental?

    I guess the bigger question is, if your vent is set to a higher setting at which you get heat at the radiator, is the vacuum a problem? I have to ask that.
  • bill Nelligan
    bill Nelligan Member Posts: 5
    air valves

    They are vent-rite #1 air valves
  • bill Nelligan
    bill Nelligan Member Posts: 5
    air valves

    It starts right when the off cycle begins, the radiator is still hot. While it is drawing vacuum you can turn the dial to 1 or 2 (slow) and the vacuum will stop, if you then turn the dial back to 6 (fast) the vacuum begins again. If you leave the setting at 6 the radiator funtions fine, the vacuum lasts about 10 minutes and is noisy. When I bought the house the system was banging leaking mess, now thanks to the book and this site it was quiet and working fine, I can live with the noise but would like to know why it started and is it a sympton of other problems.

    Thanks,
    Bill
  • Brad White_9
    Brad White_9 Member Posts: 2,440
    Bill, when you say

    that the vacuum will stop, do you mean the sucking of air stops (vent closed off)? Or that the actual vacuum is gone?

    Is the noise a hissing noise? That may mean you need a larger vent. But I hazard to say that because the radiator is hot, so is the vent and it is closed. If noisy upon release, a larger vent may serve you better.

    If the adjustable vent is the culprit (artificially low orifice for balancing), might I suggest a TRV with a fully open vent instead? This way you can enjoy the temperature balance you probably seek with the adjustable vent yet allow a big gulp when the cycle ends.
  • Norm Harvey
    Norm Harvey Member Posts: 684


    How are you testing the vacuum?
    I'm not sure were talking the same lingo here.

    All radiator air vents for one pipe steam have a vacuum breaker function,.. they are reated by psi, for example, a given valve may be rated to break its vacuum at say 1/2 psi,..

    If your cut in on your pressuretrol is set for a number higher than that point, the valve will never open and break vacuum because the pressuretrol never lets the burner stay off for long enough to let the pressure fall to what the valve is rated for.

    what are your pressure troll settings?

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  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    Another question

    are your steam mains insulated?

    If not, steam will condense therein and aggravate the vacuum noise. The lack of insulation also wastes a lot of fuel.

    Brad, you are correct- 1 is the lowest setting on a Vent-Rite #1 adjustable vent.

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  • bill Nelligan
    bill Nelligan Member Posts: 5


    i am testing the vacuum by putting my finger on top of the vent rite, I will put a vacuum gauge on it tomorrow. Pressuretrol is set at 1/2, tried to find the specs for vent-rite #1 but web site is not helpful.
  • bill Nelligan
    bill Nelligan Member Posts: 5


    Brad,

    The sucking of air stops.
    The noise is a hissing noise which I assumed was cause by exhaust from a dirty valve, but it is definetly a vacuum, will measure tomorrow. What is a TRV?

    Thanks,
    Bill
  • Vermonter_3
    Vermonter_3 Member Posts: 21
    What valves do you have on your mains?

    I had a similar problem on a few of my radiators, sizing the main vents correctly solved the problem.

    My best guess is that the undersized main vents couldn't let enough air back in fast enough so it had to compensate somehow. I'm sure that air didn't care if it went in through the vent on the radiator or the vent on the main, it just wanted in!
  • Brad White
    Brad White Member Posts: 2,399
    TRV

    Bill, sorry for the lingo, a TRV is a Thermostatic Radiator Valve or in the case of one-pipe steam, a Thermostatic Radiator Vent Valve.

    This device (valve) screws into the vent tapping of the radiator. The vent itself screws into the body of the valve.

    The valve acts as an itermediary between the radiator and the vent, allowing air to be released to the vent based on space temperature.

    I like the Macon OPSK model or the Danfoss type. What is key is that the good valve brands have a vacuum breaker built in. And vacuum is a hot topic to you!

    Brad
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
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