Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

These air vents suck!

I agree with your diagnosis,but, if it's a long enough runthat may also be undersized, it will suck air at the end of every cycle. I don't think that insulation will completly solve the problem. I feel that a vaporstat would be a better alternative. If the pressure doesn't build as high, there won't be such a vacuum action.

Anthony Menafro


    STEVE PAUL_3 Member Posts: 126

    Last year we installed a Burnham gas steamer to replace a cracked old timer that was 250% oversized. The one we installed was the correct size (10-15% oversized based on EDR) All radiators heat quickly and well, the system runs very well. The problem is after the system shuts down, a radiator vent sucks air in loud enough to disturb the customer. Obviously, the steam is condensing and forming a vacuum. I suspect the problem is similar to "Panting" vents caused by sludge in the runouts. But the vent does not pant, it only sucks on shutdown. I hope the wall can help. I want to give the customer some degree of hope to a solution without a lot of guessing and indescriminate parts changing.
  • Tom_42
    Tom_42 Member Posts: 63
    cutouts setting

    What's the cutout setting?
  • Boilerpro_3
    Boilerpro_3 Member Posts: 1,231
    Check the main vents

    Vents like the Gortons don't open right away when the steam shuts off. You may want a Hoffman or a check valve to let the system breathe back in easily at the mains instead of the radiators.

    STEVE PAUL_3 Member Posts: 126

    cut in at .5 out at 1.5
  • Steve Garson_2
    Steve Garson_2 Member Posts: 708

    I have the exact same problem. This past weekend I installed a vacuum breaker in a manifold with the main vents. It didn't solve the problem. I'm clueless as to what to do now.
    Steve from Denver, CO
  • Are the steam pipes insulated?

    if not, steam will condense in them quickly and cause the vents to suck air on shutdown.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Steve Garson_2
    Steve Garson_2 Member Posts: 708

    I just upped the insulation from 1/2-inch to 1-1/2 inch. Only eight feet in a finished ceiling still only has 1/2-inch. I even insulated the returns. Why would this happen with a new boiler when the old one had no problem? Is it from the fast steam not completely heating up the pipes?
    Steve from Denver, CO
  • T-O
    T-O Member Posts: 29

    Can you ask the customer if he had this problem with the old boiler? Most likely you inhereted an old problem. The pressutrol settings are just right. You said that all the radiators are heating up quickly and well. If the radiator with the sucking noise the larger unit in the house? Is it on the first floor? Next time the it is heating up touch not only the top, but also from the top to all the way to the bottom and do this from the feed side to the air vent side. Is it heating up more secions on the top than the bottom? Let us know
  • gerry gill
    gerry gill Member Posts: 3,078
    do you think

    the new boiler is generating alot more steam? quantity wise? thereby making more to condense..

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Christian Egli_2
    Christian Egli_2 Member Posts: 812
    Hanging in the cold

    Steve, I am so sorry the vacuum breaker did not solve your problem. Is it at least helping a little? Does air get sucked into it on shut down? Is it an adjustable vacuum breaker and if so is it adjusted to its lightest setting?

    Old versus new

    The old boiler was large, it was heavy, and it contained relatively lots of water. All this make for slow cool down time.

    The new boiler is light, quick, and has no water content to speak of. As soon as the fire goes out, the steam goes flat and the whole boiler freezes nearly instantaneously.

    What can aggravate the case even more is the draught the chimney provides. Old chimneys provided great draught on little heat. Very simple and effective, you build a good chimney and you don't need an electric draught blower - this was particularly convenient in the times prior to electricity.

    So this powerful chimney straddles the boiler and it pulls everything it can. This forced draught does not stop for probably half a day (or way more) after the fire is turned off.

    The old boiler had enough heat packed within its mass to coast until the next firing. The new low mass boiler does not have what it takes and it gets blown away.

    Fortunately there are ways to control and limit the between cycle draught. Think vent hood, think barometric damper, think flue damper. Any of these, with varying success, limit the effect of the chimney on the boiler itself, and that includes in between cycle cooling.

    Why is this perhaps important to your problems?

    Because if the new boiler is already meant to cool off faster by design and you add a powerful chimney to even draught-cool the shivering boiler, then it is that much more understandable that the boiler becomes the first spot in your system to go ice cold. With the rest of the system all insulated, and the radiators sitting in the nicely warmed rooms, the boiler flue passages is your bare butt sticking out in the cold.

    And with steam now regrouping at the boiler, vacuum appears real quick.

    Anyway, that's more talk that I hope will get all of you closer to a solution.
  • adayton_2
    adayton_2 Member Posts: 130
    STEAMHEAD ?? Pressuretrol cutout

    0.5 to 1.5 PSI sounds like you have a stock Pressuretrol. Consider installing in its place a Honeywell VAPORstat with cutout set from 0.5 to 0.9 PSI. This should be all the pressure you need to heat a residence.. I do not know if this reduced pressure will help abate the steam condensing "sucking" noise BUT, at half the pressure I would GUESS the overall volume of condensate problem should be somewhat reduced (along with slight reduction in the HO fuel bill from operating at lower pressure)..What you think Steamhead?????..

  • Steve Garson_2
    Steve Garson_2 Member Posts: 708

    The vacuum breaker did not help at all. It's installed on the main, around fifteen feet from the single radiator with the vacuum "whooshing". I can only guess that the intake venting of the radiator air vent is just enough to prevent the vacuum breaker from opening. I'm at a loss right now.

    Maybe there is a radiator vent that doesn't open as quickly, which might allow the vacuum breaker to do it's job better?
    Steve from Denver, CO
    EBEBRATT-Ed Member Posts: 15,331

    Why not use a check valve as boiler pro suggested??
  • Steve Garson_2
    Steve Garson_2 Member Posts: 708

    I never had the problem with the old boiler.
    Steve from Denver, CO
This discussion has been closed.