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Venting Like a Hissing Snake

Good day all!

Need the pros here. I have a Utica that is about 3 yrs old. Installed it myself and believe all the piping is correct as I followed the installation manual and read the tips here.

However, as of late, there are a couple of rads that are hissing loudly on the second floor. One in particular hisses, clangs and then stops; 10 seconds later it does it again. I dont believe it is water hammer as I checked with a level and it is sloped half a bubble to the valve. The Hoffman 40 is new and started after I replaced the old POS vent.

One thing I also have done; the mains are 37 feet long with 2.5" dia pipe. Venting was only done with a Hoffman 75. I had three gorton 1's laying around so I antlered the hoffman with the three gortons on the existing 3/4" elbow.

Pressuretrol is set to .5 in / 2 out. Confirmed it on the gauge numerous times.

My feeling is that I am still venting the mains thru the radiator. Dont have the problem on all of them just this one. Note that the boiler is overfired (80k btu vs 67k required based on my EDR calculations; I got a deal I could not refuse on the new boiler...)

Any thoughts here?

One thing to note: the mains were NOT insulated so I insulated the NBP and then the main about 7 feet out from the boiler. Wife will not let me insulate the balance of the main due to asthetics of our basement- "Deal with it!" is what I got.

I have become obsessed with this issue because I want to sleep at night and not hear the snakes!

Thanks in advance,

"Hey, it looks good on you though..."


  • SteamheadSteamhead Member Posts: 11,328
    Try changing the radiator vents first

    see if that helps. 
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • snakes in a radiator!

    that certainly sounds as if most of the air is being forced out the radiators. an accurate low-pressure gauge will show you the back-pressure of venting, and therefore if you need more main vents. you could remove the main vent with the boiler off, and then fire it to see what difference more main venting would make.

    can you do any down-firing on the burner if you are over-sized? if you do a search here for insulation, you will see some pictures of very nice pipe insulation jobs. while the snakes are hissing, show the pictures to your wife, and see if she will reconsider.--nbc
  • Steam_StarterSteam_Starter Member Posts: 87
    Snakes Go Away!

    Thanks guys for the ideas.

    I have a few other hoffmans that I will try switching out on the rads.  In regards to the main venting, nbc- that's a good idea.  I can open the union at the antler and see how much I get re: air (before the steam comes, wearing gloves of course) and then wrench it shut to see if that makes a difference on the second floor.

    Since i have the main vents on a 3/4" antler i am looking at the capability of 9 cfm and currently I am at 1.49 cfm.  5.43 is probably the max flow rate capacity based on good ol' Darcy's formula.  Not exactly sure since my algebra is rusty.  If anyone can give me an idea of the nominal venting capacity of 3/4" pipe that would be a great help if I am wrong.

    Looks like I am switching out to a few Gorton #2's

    As for downfiring, I have to do some more research for this Utica.

    Re: trying to sell snow to an eskimo dealing with my wife.  But she is a great cook so I don't argue too much!

    Thanks again guys.

    "Hey, it looks good on you though..."
  • crash2009crash2009 Member Posts: 1,484
    edited February 2012
    Maximized Venting

    Four and a half Gorton 2's is the max for a 3/4" pipe.  If you want or need more than that you need to increase the size of the tapping.  Here is a shortcut to the webpage of the Master of Maximizing "Gerry Gill"  There is a video to watch there as well.  I have a 1899 one pipe system with both 75 foot mains maximized.  I am happy with the results.  My backpressure has been reduced to a 1/2 ounce.  Another benefit, if you have long mains, is that the vents aid in the timely return of condensate.

    I don't know for sure if they really do this,,, but it feels like these vents reach up and suck the cold air right out of the risers. 

    Insulation is a necesary evil.  It doesn't have to look bad.  Have a look over here, you can even get the pvc in decorator colors.
  • Steam_StarterSteam_Starter Member Posts: 87
    Thanks Again Guys!


    So I was close in saying 5+ I do get it right.

    Thanks for the nice pix of the insulation. Don't think it will sway her but I gotta try!

    "Hey, it looks good on you though..."
  • Steam_StarterSteam_Starter Member Posts: 87
    Thanks Again Guys!


    So I was close in saying 5+ I do get it right.

    Thanks for the nice pix of the insulation. Don't think it will sway her but I gotta try!

    "Hey, it looks good on you though..."
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