Main vents at end of dry return vs. at end of mains?

Pete_18

One of the steam experts I had come out to evaluate my system would like to vent my unvented one-pipe steam system at the end of the dry returns over near the boiler vs. at the end of the mains.

Does anyone have any experience with this and how I can expect this to perform vs. venting at the end of the mains?

John S.

Usually on a one-pipe system, the return is not long enough to cause a problem venting it there. It just may require more vents or higher capacity vents due to the extra volume of air in the returns. Some of the pros will hopefully be able to provide more insight.

Personally, on my one-pipe system, I have vents at the end of the dry return which is only about 25' of 1 1/2" pipe. The system runs very well.

Fred Harwood

venting returns

Why let steam go any further than necessary, especially into an uninsulated dry return?

Pete_18

Good question

That's why I'm asking you guys. I just got Dan's book today, but there was no mention of this practice in there.

If venting at the end of the dry return vs. the end of the mains means I need to insulate another 40+ ft of return pipe and I'm 'wasting' steam by attempting to send it down the return, especially when a lot of it hugs the floor and some of it is buried and is physically impossible to insulate, that isn't something I'd look forward to. I'm kind of tired of insulating, fiberglass is only fun for so long.

John S.

Fred,

I agree, however, I believe ideally you wouldn't have a dry return (other than the steam main) on a one-pipe system. The only reason my system has one is because rads were removed (at some point) on the end of the main.

My only concern would be what happens to all that air that's still in the piping? Could it cause uneven distribution to the rest of the system?

The way to go would be to drop into a wet return right at the end of the steam main.

John S.

Pete

Are you sure it's not a wet return? You mention that a lot of it is at floor level.

Pete_18

Sorry, you're right, sorry for sounding like an idiot. This is still my first week and a half with steam heat and I'm still learning.

It is a wet return since it drops below the water line. Now I'm really lost as to where he was recommending we vent the system if it's not done at the end of the mains.

He was specifically referring to the end of the dry return over by the boiler, but in a one-pipe system, the dry run is supposed to be the same as the steam main. It runs across the building and then drops down and becomes a wet return, so I don't get where it would be vented if it's not done at the end of the the long main runs.

Lurker_2

If your returns are below the waterline

Then you don't have any dry returns anyway. Following the pipes from your boiler, you should see, with the bracketed items being potentially not there:

Boiler -->

Header -->

Main (generally fatter than the returns) -->

[dry return] (generally skinnier than the main, after the last radiator, and still above the waterline as it returns back to the boiler) -->

[wet return] (generally skinnier than the main, after the last radiator, and below the waterline) -->

Boiler (via hartford loop and whatnot)

In my system, as an example, I have about a 20' main of 2" pipe, which turns around (without really dropping much in height) into a dry return (1" pipe), which goes the 20' back to the boiler. It then drops down to the floor for the span of about 6 inches forming a nominal "wet return" before rising back up into the hartford loop and into the boiler. My vents should be placed at the end of the main before the dry return, since there's no point venting the return portion. However, it's not a terribly big deal (though it's not ideal) to put the vents at the end of the dry return, keeping in mind there are more bends in the pipe and more air to vent.

Other systems commonly run:

Boiler --> header --> Main --> wet return --> Boiler

In this case, the piping drops down to the floor right after the last radiator. In this case, you have to put your vents after the last radiator.

-Michael

Lurker_2

If your returns are below the waterline

Then you don't have any dry returns anyway. Following the pipes from your boiler, you should see, with the bracketed items being potentially not there:

Boiler -->

Header -->

Main (generally fatter than the returns) -->

[dry return] (generally skinnier than the main, after the last radiator, and still above the waterline as it returns back to the boiler) -->

[wet return] (generally skinnier than the main, after the last radiator, and below the waterline) -->

Boiler (via hartford loop and whatnot)

In my system, as an example, I have about a 20' main of 2" pipe, which turns around (without really dropping much in height) into a dry return (1" pipe), which goes the 20' back to the boiler. It then drops down to the floor for the span of about 6 inches forming a nominal "wet return" before rising back up into the hartford loop and into the boiler. My vents should be placed at the end of the main before the dry return, since there's no point venting the return portion. However, it's not a terribly big deal (though it's not ideal) to put the vents at the end of the dry return, keeping in mind there are more bends in the pipe and more air to vent.

Other systems commonly run:

Boiler --> header --> Main --> wet return --> Boiler

In this case, the piping drops down to the floor right after the last radiator. In this case, you have to put your vents after the last radiator.

-Michael

Lurker_2

If your returns are below the waterline

Then you don't have any dry returns anyway. Following the pipes from your boiler, you should see, with the bracketed items being potentially not there:

Boiler -->

Header -->

Main (generally fatter than the returns) -->

[dry return] (generally skinnier than the main, after the last radiator, and still above the waterline as it returns back to the boiler) -->

[wet return] (generally skinnier than the main, after the last radiator, and below the waterline) -->

Boiler (via hartford loop and whatnot)

In my basement, as an example, I have about a 20' main of 2" pipe, which turns around (without really dropping much in height) into a dry return (1" pipe), which goes the 20' back to the boiler. It then drops down to the floor for the span of about 6 inches forming a nominal "wet return" before rising back up into the hartford loop and into the boiler. My vents should be placed at the end of the main before the dry return, since there's no point venting the return portion. However, it's not a terribly big deal (though it's not ideal) to put the vents at the end of the dry return, keeping in mind there are more bends in the pipe and more air to vent.

Other systems commonly run:

Boiler --> header --> Main --> wet return --> Boiler

In this case, the piping drops down to the floor right after the last radiator. In this case, you have to put your vents after the last radiator.

-Michael

Pete_18

Drops down to the floor right after the last radiator

http://forums.invision.net/Index.cfm?CFApp=2&Message_ID=199164
See pictures in the above thread

After the last radiators, each of the two mains drop to the ground and then return to the boiler, so this appears to follow the later part of your email.