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Where to start with venting a 2-pipe steam system?

I'm looking to replace (and most likely add) venting to my steam mains. As I mentioned in previous posts I had radiator vents on my two pipe system and barely any actual main vents. There were a few as well as some additional traps, but the remaining rad vents really sing when the system comes on due to poor venting.

I know I need to measure the length of my mains to calculate how much air I need to expel and select vents accordingly, but what else do I need to know? Is there a primer on exactly how to measure the mains, the best way to install the vents, or anything else I may not think of? I don't trust that the system was ever vented as it should have been so I don't want to just find and replace. I did see Rod's pdf tutorial on building and installing an antler system with Gorton #2s that I was going to use. 

I have Steamhead coming out mid-February to get my system on track, but if I can move in the right direction before he comes that would be great as my system has so many woes. Any basic instruction would be greatly appreciated.
twice the boiler I need, short cycling, atrocious near boiler piping, excessive fuel consumption, water hammer throughout...you name it I got it in my system O_o

Comments

  • Meaning...

    Let a pro handle it? Or are you saying I don't need main vents?
    twice the boiler I need, short cycling, atrocious near boiler piping, excessive fuel consumption, water hammer throughout...you name it I got it in my system O_o
  • Paul48
    Paul48 Member Posts: 4,470
    Saying

    As you can see from the proper setups, Steamhead will have to do some work to get your system right. You might be wasting money,putting a bandaid on an open wound.
  • Jamie Hall
    Jamie Hall Member Posts: 17,164
    Oh indeed you do need main venting

    The question is... where?  Not so much how much -- it's almost impossible to over vent a system -- but there are really two basic flavours of two pipe steam.



    Both need venting on the dry returns; that's how the air in the radiators gets out of the system.  That's easy enough (you still base it on the size of the steam mains, not the returns).



    However... some two pipe systems have what are known as "crossover traps".  These are very like -- in fact, usually are -- thermostatic radiator traps, but they are installed at the ends of the steam mains by going up from the main, over to the trap, and then the outlet of the trap goes down to the dry return at the same location (condensate is taken care of in these systems by drips to wet returns).  Systems which are piped like that do not need vents on the steam mains, as the crossover trap has ample capacity; the vents on the dry returns take care of the actual venting.



    If there aren't crossover traps -- or some dingbat took them out once upon a time -- then you do need main vents at the ends of the steam mains as well as venting on the dry returns.



    So... as I say, the question is, where.



    On the other hand, if you're feeling lazy and have Steamhead coming over... just sit back and learn when he gets there!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Gotcha...

    As ol' Clint said, "a man's gotta know his limitations." ;)  Thanks Paul!
    twice the boiler I need, short cycling, atrocious near boiler piping, excessive fuel consumption, water hammer throughout...you name it I got it in my system O_o
  • That main ends with a trap...

    that leads to a return. Does that mean I don't need venting there? Considering that the trap hasn't been replaced in at least a decade should that be done?

    The room above this steam main end has one of 2 rads that are cold. I was hoping that proper venting would allow this room to heat up as it should since it's our TV/living room where we spend a good deal of time.

    I have an extensive steam/water leak or leaks in the system and I was hoping that venting would offset that a bit until I found the leak and repaired it. Basically, I'm just trying to do what I can and get the system to limp along and minimizing damage until the pro arrives. I believe I've opened Pandora's box with this system!
    twice the boiler I need, short cycling, atrocious near boiler piping, excessive fuel consumption, water hammer throughout...you name it I got it in my system O_o
  • Steamhead
    Steamhead Member Posts: 14,863
    I hadn't seen that pdf before

    looks like Hoffman is really pushing converting gravity-return systems to pumped-return. We would never do this, since it adds mechanical complexity that we can avoid by just keeping the pressure low.
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Steamhead
    Steamhead Member Posts: 14,863
    We'll get it humming again

    hang in there! And thanks all for the kind words.
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Will do!

    I can't wait to have you go over this system! I'll be in touch with you shortly with all the pics you requested by the way. Between Christmas and a sewer line failure I've stayed pretty busy as of late. Gotta love old houses!
    twice the boiler I need, short cycling, atrocious near boiler piping, excessive fuel consumption, water hammer throughout...you name it I got it in my system O_o
  • PMJ
    PMJ Member Posts: 1,122
    2 pipe venting

    I have a 2 pipe system and don't have anything on the steam main - either a trap or a vent. There is only one vent in the whole system and that is on the dry return.



    Maybe it is the size of my main and maybe it is because it is in a loop around the entire house, but I don't see the need for a vent on the steam main in a 2 pipe system. To me, since the traps on the radiators are never closed (except for maybe on the very small ones in a lavatory or something), the whole system is basically wide open to the atmosphere through the dry return vent at all times. If the pipes are big enough there is minimal resistance to the steam pushing the air through the rads and out the vent. Finding out if you have any resistance or not is not a guessing game. If the air is having trouble getting out anywhere there will be pressure trying to push it. So measure the pressure anywhere you are wondering about it. Or, the poor man's pressure gage - your ears - will give you the answer too. I never hear a sound at my dry return vent and I have never seen even 2 oz of pressure in the main at the farthest point of the loop from the boiler.

    Perhaps someone could tell my why my system seems so different than those I read about here. I am looking for the reason(s) why I am able to get this whole thing done easily at 5 oz or less at the header, no steam main vent, and no vaporstat (there is one but I don't use it). My farthest rad is 20 minutes from steam firing a dead cold system and maybe 90 seconds from fire during cycling. When I moved in there was a steam main vent that hissed loudly and several on rads. I removed them all, turned the dry return vent into a direct opening to the atmosphere with a solenoid valve,and everything got better. Its not like it is a really small system either - 460MBTU input - about 1000EDR.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
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