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Newbie needs new vent advice

Hi everyone, thanks for sharing your knowledge, this is a great forum. I plan on buying the book(s) but meanwhile I need to have heat for Christmas. My house is a 2 story brick, built in 1914, gas, with a Slantfin Galaxy boiler with 4 cast iron radiators, one in the front of the house on both floors, one in the back of the house on both floors. Middle of the house has a riser through the bathrooms.


Every year it's the same, perfect heat until the temp drops below 32 and then something goes wrong. We had uneven heat with one end of the house having hot radiators and the other stone cold. I replaced the vents on first one and then all the radiators and that helped for a day or two. The riser in the bathroom in the middle of the house is hot, so I know the heat is there and can rise. I replaced the thermostat, which suddenly died, an old Honeywell dial with the same type. To get heat I have to set it to 85 and that's keeping one end of the top floor comfortable and the rest of the house cold. There is a Dole 9 vent on the return (hope that's the right terminology) in the basement that's the furthest from the boiler. It usually hisses a lot once it gets to 32 outside, but it's been silent, so I am thinking it would help to replace it. I'd like to get it locally rather than wait for a delivery. Someone working on my house already said it was the wrong size, because it was hissing. What should I replace it with? Any other comments/suggestions welcome.



  • RodRod Posts: 2,067
    More info

    Hi- We need a bit more information on your steam system. The "Dole 9 " doesn't ring a bell as it isn't in any steam charts I have. Maybe one of the pros is familiar with it.

    You mentioned just the one vent . Do you have main vents on all your main steam pipes?

    If not this would be the first thing you should correct.

    Could you also tell us what type of steam system you have - 1 pipe?  2 pipe? (this is determined by how many pipes go to each radiator)

    At what steam pressure does your boiler normally run? It should be at 2 PSI and preferably under. You might want to post some pictures of your boiler and its piping and things like the "Dole 9 " vent. The pictures will help us understand your system better and make recommendations.

    - Rod
  • BobCBobC Member Posts: 4,406
    first steps

    First of all do you know what pressure the boiler is running at? It should be running at less than 2PSI. If it is too high it gets expensive and you can run into a problem where the vents can't open again after the initial blast of steam because high pressre keeps the vent shut even though that radiator is not hot. On the front of the boiler there should be a 3" square grey box that's called a pressuretrol, the tab on the front sb set to 0.5PSI and the white dial inside should be set to 1PSI.

    You said your main vent in the basement was a dole #9. That has to be an old vent and it is probably too small to do the job. If you can tell us how long the steam main is and about what the outside diameter is we can tell you what size vent you should have there.

    Also post some pics of the boiler from a few different angles so we can see the piping coming and going from it. Also post a picture of the steam main and the vent on it.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • radiant_babyradiant_baby Member Posts: 4
    Here's the details

    Rod and Bob, thanks for the replies and for your patience. We have a one pipe system, with only one vent, the aforementioned Dole #9 on the return, about 36 feet from the boiler. The diameter of the main is 7.5" and diameter of the return is 5.25".

    There are Hoffman No. 40 vents on the radiators. There is a much painted vent on the riser in the bathroom on the second floor also, but since the riser gets hot, I didn't change it recently.

    So the pressuretrol was set at 3 psi with the white dial "diff" set at 3. Something tells me you are laughing at that. But it was set by the guy who installed it and was never touched. I just chaged it to .5 psi and the dial to 1 as recommended.

    Here are the pictures:
  • radiant_babyradiant_baby Member Posts: 4

    The pressuretrol was originally set on 4, since it is marked with lines with 2 increments on the psi side.
  • BobCBobC Member Posts: 4,406
    Next steps

    Good job on getting that pressuretrol set to the right levels. That should make a real difference on how the system works.

    Do you have the installation manual on that boiler? the header does not look right and I can't tell if you have a hartford loop or not. I've attatched a slatfin installation manual (i'm not sure if it's your exact model but it sb pretty close) and page 7 details how the near boiler piping should be configured.

    Once everything is working fine you want to insulate all the piping in the cellar with a minimum of 1" pipe insulation.

    That main is a 2"ID if it measures 7.5" in circumference. 36 ft gives us about 0.79 cu ft plus the boiler header and the boilers steam chest. A Hoffman 75 might do but for less money you can replace that main vent with a Gorton #2 and get over 3X the venting rate. The Gorton's need a 1/2" female fitting to mate with so you would have to put a 3/4 to 1/2" reducer to mount the vent on.

    Also since that pressure was set too high for a while make sure all the radiator vents are working right.

    Vent your mains quickly and the radiators slowly.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • radiant_babyradiant_baby Member Posts: 4
    learned a lot!

    Bob, thanks for the information and the pdf. I'm going to try and pick up a Gorton vent tomorrow. I'll compare the correct piping with mine as well.
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