steam main vents

Nate Perkins

I am quoting a replacement steam boiler in an old house. (Taking out old Timken oil fired boiler).
Customer complains of uneven heating

Currently, steam main vents are at the end of 3/4" dry (above water line) condensate return lines at back of boiler.

Ends of 2" steam mains have been drilled and tapped in the side and a 1/8" air vent installed vertically.
I am considering installing 2" x 1/2" Tees 15" back from ends of mains for new Steam vents

Question: Are existing vents at drop in condensate return adequately removing air from main? Or am I on the right track?

kevin coppinger_4

I'm no expert....

but sounds like they used radiator vent instead of main vents on the main....that won't do...you are on the right track. kpc

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Steamhead

To answer your question properly

I'd need to know if this is a one-pipe or two-pipe system. If two-pipe, are there air vents or traps on the radiators?

Then I can tell you where the vents should go, and how to size them.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Nate Perkins

One Pipe

Sorry, I left out the most important part.
System is a one pipe, I know that the proper point for main vents is 15" back from ends of runs.
And I am prepared to put them there if necessary.
But.... When I am standing in the basement and imagining the interaction of steam, air, and condensate I am wondering if those large vents on the ends of dry returns are not functioning to remove enough air so as to make cutting into those 2" mains an expensive exercise with little real value to the consumer?

My first reaction is that once condensate reaches the ends of steam mains and starts to fill returns then there is no place left for air to move back toward vents. (also, the air will probably not move willingly down the pitched 3/4" condensate returns).

I almost think that putting them there just allows steam pressure from the boiler to drive water back up the returns.

Steamhead

How Long

are your steam mains, and whar size pipe are they? Also, how long are the 3/4" dry returns from the steam main connections to the vent locations?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Nate Perkins

Pipe Sizes

Thanks for responding:

Steam mains are piped in an "H" pattern with boiler at the center of "H". From steam riser on boiler to each leg of H is approx 20-25' developed length of 2" steam main with an equal amount of 3/4" back to steam vent.

Total standing load is 356 sq feet of mostly column type radiators with 1-1/4" run-outs to rads.
Largest singlw rad is 56 sq ft.