Main vents question

Joe_9

Hello,

I have a one-pipe steam system in my house. I am confused by what you call "main vents". I don't seem to have any vents on the mains, but I do have vents on the returns that come off the mains. These vents are directly above where the return makes a 90 degree turn, becomes vertical, and heads down to the boiler. From there the returns connect to some other piping that originates from the headers but turns down below the gauge glass, connects to the returns, and enters the boiler. I'm assuming that the purpose of these vents is to release air at the end of a cycle so that condensate can flow back to the boiler easier.

Here are my questions:
1) Wouldn't these vents also cause steam to find a path of least resistance directly into the returns? I'm guessing this isn't a problem just because the returns meet up with the mains further on and then the steam would be back in the mains (and hopefully not taking water with it).
2) What size vents should I use for these vents? As big as I can? Or the same size as the vents on the radiators?
3) Because I have vents on the returns, does this mean that I don't need vents on the mains?

Thank you all very much for your help -- this forum is a Godsend for people like me who didn't know that there was a difference between a hot-water system and a steam system before I became a homeowner just a year ago.

Unknown

Hi Joe,

Check out the menu at the left. Specifically, the "Steam Problems?", and the "Hot Tech Topics" for the steam "stuff".

Here is a sample of what's there...

http://www.heatinghelp.com/steam_airventsmakenoise.cfm

Alan(CaliforniaRadiant)Forbes

Those are

your main vents and they are located at the end of your returns so that steam will push out as much air in the system as possible. As soon as steam hits those vents, they will stop venting.

Sizing? They should be the same size as the piping coming off the tee; don't bush or reduce them down. On residential systems, it's usually 3/4" or 1".

Don't use radiator vents for your main vents; they are too small and it will take forever to get the heat going.


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