two pipe naturally induced vapor/vacumm system

Ed Tretter

I live in house that was originally built in 1907 and had an addition built around 1937. It is steam heated house originally using coal now oil. It is a rather large house.

After numerous suggestions and lots of research I have deduced - thanks to your book - that it is a two pipe naturally induced vapor/vacuum system using the Arco model K values. Understanding vacuum systems on old cars, I went through the entire house replacing the vents which someone put on a few of the Arco valves in place of the hex nuts on the radiators. I have also removed the two way vents in the boiler room and replace them with Hoffman vacuum vents. This has helped as a few radiators that were dormant now fire up.

I still have one room that refuses to heat unless I turn off one of the radiators in the room below it. Also, again thanks to your book, I have realized that there are orifice screws that are adjustable...but how does one know what the appropriate adjustment would be?

If you could shed any light on my dilemma I would appreciate it as for the past week I have been waking up in a cryonic state.

Thanks in advance.
Ed

Steamhead

There should not be

any vents on the radiators. On this system the proper replacements for radiator vents are 1/8" pipe plugs.

Vacuum main vents worked great on coal but aren't so good with oil or gas. I'd go with standard main vents.

Are your slow radiators way out at the ends of the steam mains? If so, properly sized steam main vents will help a lot. Measure the length and diameter of each steam main and we can tell you what you need.

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

Ed Tretter

two pipe naturally induced vapor/vacumm system learing curve

Thanks for your quick response. Here are the answers to you questions…

1. There are no vents on the radiators. I have the Arco Model K orifice system type valves. I would like to know what the adjustment should be on the orifices (the screws inside). I imagine that it has something to do with the size of the radiator as well as its placement from the boiler. Also, a few of the valves are leaking at the stem. Can they be repacked?

2. I don’t know what standard main vents are. If they are 2-way vents vs. 1-way vents, installing 2-ways would go against the natural properties of a vacuum system. Can I go from vacuum vents to 2-way?

3. Oddly, the slow radiators are relatively close to the boiler room and in the middle of a series of radiators that are functioning. Regarding properly sized steam main vents – my house is similar to Fig. 60 on page 269 of your book. Except, unfortunately for me, it has twice as many radiators. Nevertheless, the concept is the same. I do have a Hoffman vacuum vent at the end of the pipe in my garage as well as 2 in the boiler room. The ones in the boiler room are on separate “T’s” or “Y’s”. Each of these as one Hoffman valve and a plug on the other branch. See attached picture.

I am under the impression that a vacuum system needs to be contained, which is why I have been replacing the 2-way valves on the radiators with plugs, with the exception of the Hoffman valves on the mains. The results have been mixed – some dormant radiators are now working as the radiators in the garage have stopped functioning. To mention only a few radiators had what I refer to as silver bullet valves/vents sticking out of the Arco valves where the hexed nuts should be.

Finally, I would like to know that the proper psi should be for the system. I currently have it set @ 4psi.

Thanks.

Ed Tretter

2-Way Naturallly Induce Vapor/Vacuum System Learning Curve

Thanks for your quick response. Here are the answers to you questions…

1. There are no vents on the radiators. I have the Arco Model K orifice system type valves. I would like to know what the adjustment should be on the orifices (the screws inside). I imagine that it has something to do with the size of the radiator as well as its placement from the boiler. Also, a few of the valves are leaking at the stem. Can they be repacked?

2. I don’t know what standard main vents are. If they are 2-way vents vs. 1-way vents, installing 2-ways would go against the natural properties of a vacuum system. Can I go from vacuum vents to 2-way?

3. Oddly, the slow radiators are relatively close to the boiler room and in the middle of a series of radiators that are functioning. Regarding properly sized steam main vents – my house is similar to Fig. 60 on page 269 of your book. Except, unfortunately for me, it has twice as many radiators. Nevertheless, the concept is the same. I do have a Hoffman vacuum vent at the end of the pipe in my garage as well as 2 in the boiler room. The ones in the boiler room are on separate “T’s” or “Y’s”. Each of these as one Hoffman valve and a plug on the other branch. See attached picture.

I am under the impression that a vacuum system needs to be contained, which is why I have been replacing the 2-way valves on the radiators with plugs, with the exception of the Hoffman valves on the mains. The results have been mixed – some dormant radiators are now working as the radiators in the garage have stopped functioning. To mention only a few radiators had what I refer to as silver bullet valves/vents sticking out of the Arco valves where the hexed nuts should be.

Finally, I would like to know that the proper psi should be for the system. I currently have it set @ 4psi.

Thanks.

Steamhead

I turned up the brightness a bit

so we could see this system a bit better.

Toward the right, we see a rack of piping or maybe a cast-iron manifold that used to have two vents on it. The left side appears to be plugged and the one on the right has what looks like an old Arco vent. These were likely the original dry-return vents for this system.

Toward the left we see what looks like a Hoffman #76 vacuum vent- is this the one for the garage? If so does it vent the steam main or the dry return?

If the radiator inlet valves have vents on them, remove the vents and plug the holes. The orifices should be set so the radiators are a bit less than completely full of steam at a pound of pressure. The Arco information I have says this system should run between 6 and 20 ounces of pressure.

It also says that this system was "open to the atmosphere" and did not run vacuum. There might have been variations that did run vacuum, but you should be able to use "2-way" vents with no problems at all.

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