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Balancing Steam Systems - Pressure Question

bostonJohn Member Posts: 4
edited October 2018 in THE MAIN WALL
Brand new steam system owner here. I have a one-pipe system and some of the radiator vents are clogged entirely and I'm pretty sure the main vents are as well. This system is able to heat 2 radiators (of 6 total) to screaming hot and the rest are ice cold. I will make another post about appropriate radiator vents to buy once I can take pics of each radiator because they're all different.

In the mean time, I just got done reading The Lost Art, and I'm looking at the Balancing Steam Systems Using a Venting Capacity Chart PDF and I have some questions.
  1. Should I run this test regardless of whether the radiator vents are working appropriately?
  2. When I start the boiler with the main vents off entirely, what should I do about the radiator vents? Open them full blast? Close them? Right now I have adjustable radiator vents, but I was planning on getting Gorton vents that aren't adjustable.
  3. The chart describes the CFM air flow at certain ounces of pressure. How do I know what oz I'm using in this case? I have the cut-out at 1.5 psig on the boiler. How do I determine oz from that?
  4. My main is cast iron, but the returns are copper. These venting capacities are for steel pipes - does that matter?
  5. I kind of have "3" mains and 3 returns that are vented by 3 vents. They are all served by the same boiler, but the header splits the main to go in two directions and the there's a third main that branches off from one of those that connects directly to the header. Each of these branches has its own dry return with its own vent to a common wet return. Would I be taking all of the main vents off at once, or run the test 3 times with a different vent off each time?
Alternatively, I could just do a simpler question: Can I just buy 3 Barnes & Jones Big Mouth main vents and call it day? They're not terribly expensive each and they have the most venting capacity on the list. Would that cause any problems?

Any advice about sizing main vents (or about getting this system working correctly more generally) is greatly appreciated. The previous owners of this place payed $600/month to heat 1000 sq ft. That seems insane to me, so I'm trying to make this system work as efficiently as possible.


    JUGHNE Member Posts: 11,075
    It is best to not make another posting for the same system.
    Adds to the confusion. IMO

    Just add more items in the very top header later.
  • gfrbrookline
    gfrbrookline Member Posts: 753
    What size pipes do you have on your mains and how long are they?

    One Big Mouth will vent about 40' of 2" pipe if they are placed on the end of the mains. If you are venting on the ends of the dry returns you will need to vent heavier to make up for the additional air in the dry returns. I have my vents just before the end of my dry returns, 60' main has 3 Big Mouths, 50' has 2. I also have dripped returns, one 40' that has 1 Big Mouth the other is 30' but only feeds 2 small sunrad radiators which has a Gorton #1. It was a trial and error job but all of my heat is balanced and the 0-3 gauge on my boiler rarely reads above 10oz.

    You need to vent the mains properly, once that is done you can determine what you will need for radiator vents based on the heating characteristics of the room and the size of the radiator. I would use Ventrite No. 1's for this so you can dial the radiators in. If you have a room that is still under heating you can look at a Gordon 6 or c.