What exactly is defined as main piping in 1-pipe steam system heating 2nd story and up?

zigloo99

I'm trying to understand what piping is considered Main Piping in a one pipe system to determine if my main vents are in the right locations. Where I'm confused as considering are the pipes to the radiators are on the 2nd and 3rd floor in a mulit-family considered main pipe and should have main vents incorporated somehow and if so, do you vent into an attic? Or is it the ends of the larger piping, in my system 2" piping", where there is an reduction elbow that goes to smaller 1" piping for the condensate return. In my system though, the condensate return lines have the main vents and seem to spit water at times and some of the radiators air vents are spitting water when they are larger vents such as Hoffman 1A adjustable or VariVents. I have Gorton # 1's on the main condensate lines. I did recently switch out the pressurol and put in a vaporstat and set it to 1.25lbs and have a 5lb pressure gauge to verify it.

My crude drawing is attached to show where my current mains are located.

Fred

The mains are those that connect to the boiler header and travel horizontally around the basement. Any large pipes that rise vertically up to the second or third floors and have multiple radiators connected to them are Risers. They can be vented near the top if the connected radiators are slow to heat. Any smaller pipes that feed individual radiators are Radiator Run-Outs and every once and a while, they may be long enough that placing a vent just before the radiator supply valve helps evacuate the air in that long run-out.

As for radiator vents spitting water, VariVents are a poor choice. They vent too fast and often spit water. The Hoffman 1A typically don't spit if set properly and if all radiators are pitched slightly back towards the radiator supply valve so water can run out. Use shims to get the needed pitch.

Another cause for water spitting out of main or radiator vents is high pressure. Set the Pressuretrol for a Cut-In of .5 and the white wheel inside to "1". For a Vaporstat, set the Main to 1.5 ot 2 PSI and the Differential to 1PSI. Also, make sure the pigtail the pressuretrol is mounted on isn't clogged. If it is, the Pressuretrol/Vaporstat can't manage the system pressure.

Fred

@zigloo99 , also, it is OK for the main vents to be either at the end of the Main, after the last radiator run-out or anywhere along the dry return.

Jamie Hall

The main vents are usually placed at the ends of the mains -- but they work equally well placed anywhere along a dry return. This for one pipe and conventional two pipe systems. Vapour systems are often done differently...