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Sizing Air Valves for a One pipe steam System in a 6 unit apartment building 25ftx80ft

el34b Member Posts: 1
Good Evening.

I hope everyone is doing well.

I was wondering if anyone could help me figure out some air vent valve sizing.

The building in question has 3 floors... 2 apartments on each floor (front and rear)... 3 radiators in each apartment.

The boiler is situated under the rear apartments and there is a vent in the basement and then a far run going to the front apartments.

each riser pipe that goes up into each apartment has a steam valve vent on the second floor, which run through the bathrooms.

The boiler is situated under the rear apartments

There is a gorton #2 main vent in the basement and then a far run going to the front apartments.

What im trying to do is figure out what size gorton air vents to put on each radiator.

The rear side of the building on top of the boiler gets hot fast.. the far size doesn't. The thermostat is in the far 3rd floor apartment.

If someone had to plan this from scratch, what valves would go on each radiator? Each of 2 bedrooms is on the furthest distance on each side of the building, and the living room radiator is right before the bedrooms.

If anyone would need any other additional information, id be happy to find it for you!



  • Put the fast vents on the return pipes in the basement next to the boiler, and put slow ones, (Hoffman 40's) on the radiators.
    Only then will you be balanced.
    Tell us what the lengths of your mains in the basement, leading away from the boiler are, and we can tell you what needs to be put on the mains.
    Main venting is most important, if you wish to avoid paying extra for fuel to pump out the air, on every cycle.--NBC
  • Dave in QCA
    Dave in QCA Member Posts: 1,776
    You mentioned that you had vents on the risers going up to the third floor, and that those vents were located on the risers as they pass through the second floor. What type of vents are these? These, if proper sized, will also help to vent the mains.

    I agree with nbc, I like Hoffman #40 vents because they are nice and slow and help to balance a system.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
  • I am sure that you will need more Gorton #2's on the mains.
    I have 6 dry returns on a one million BTU one pipe system, with 3-4 each. I am sure your system is smaller, but you will need lots of main venting. If you have a good low-pressure gauge, (0-3 psi), you can see by the back-pressure when you have enough to equal the "open pipe". You should be able to see one or two ounces of pressure while the boiler is making steam, and pushing the air out. If you see more pressure, then you know that you are burning extra gas to force the air out of constipated little openings.
    When you have the mains properly vented in such a way, then you can make adjustments to the radiator vents, which with the Maid-o-mist vents could start with the slowest orifices, and if too slow have then larger ones.--NBC