Main venting for one pipe steam

Steamhead

let the system cool down completely. Then remove the main vents and start the boiler. Steam should move quickly down the mains and out thru the vent pipes- shut down the boiler at this point. If this happens, go ahead and put the bigger vents in.

If it does not, either the vent pipe connections are beneath the system's water line so air cant vent thru them (unlikely) or the pipes have become clogged.

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Mitch Berkson

I have a one pipe steam system which works pretty well, but I wonder if it would work better with changes to the main vents. The existing configuration doesn't seem to work since I let the pipes get cool and when the boiler is turned on again, no air comes out of either of the two vents.

I removed a vent and it isn't clogged, but as a test, I replaced it with a new one. Still no air.

The vent pipe configuration looks suspicious to me. There are two main vents. Each is connected to its main at a point 4" below where the main turns down to return (the vent pipe connects with a T to the vertical pipe). There is right angle pipe from this point up to the vent so that the vent itself is a few inches above the horizontal part of the main. Since the vent pipe is connected 4" below the horizontal steam main, I don't think steam will push air out of it. Also the vents used seem pretty small - they
are Dole #95 which fit on 1/4" pipe and are more suitable for radiators, I think - but that's the largest vent I could find for that size pipe. (Of course, no air comes out of them anyway)

So my questions are:

1. Does the existing main vent piping make sense?

2. If not, would it be worth changing? If changed, I believe an appropriate configuration would be a T on the horizontal part of the mains about 15" back from the bend with a 6" nipple to a large vent. This would be with 3/4" pipe.

3. How do I decide what size main vents should be used?

I have read "The Lost Art of Steam Heating". Thanks for any help.

Steamhead

Dole 95

sounds too small. But how about measuring the length and diameter of your mains? Then we'll know how much air we're dealing with, and can suggest what vents to use.

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Mitch Berkson

Pipe length and size

One run is 25 feet and the other is 85 feet. The pipe OD is about 2.4" - so I think this is 2" pipe.

Unknown

vent replace ent

Before you knock yourself out and do something costly try this.

Install Gorton D valves, they vent a ton of air, they are for 1/4" pipe and come in angle & vertical patterns.

Jake

Steamhead

The long main

has about 3 times the air that the short one does. Use a Gorton #1 on the short main and a Gorton #2 on the long one. This should make the steam reach the ends of both mains at the same time, without unnecessary delay.

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Mitch Berkson

No air from existing vents though

Thanks. But if there's no air at all coming out of the existing vents, I'm dubious that changing vents will affect that problem. Once air is being vented though, your suggestion of using vent sizes proportional to the pipe runs makes sense.

Any opinion on whether it is possible for the vents to be effective with the vent pipes connected as I described on the vertical pipe?

Mitch Berkson

I removed the vent on the longer main and ran a brush through the vent pipe to the main, so that pipe isn't clogged. It is a new vent, so it works. Still no air comes out of it when steam comes up.

The vents are in the same room as the boiler sight glass, so I can see that the pipes are nowhere near the water level.

My main question is conceptual. With the vent pipes tapping into the mains as I described (after the mains turn down), would you expect air to be pushed out? Since steam is lighter than air, won't the steam stay in the horizontal main and fill the risers and radiators before the steam is at the lower level where the main vent pipe connects to the system?

Or should the air be pushed out just as a result of pressure building in the system even with the pipes in this configuration?

Steamhead

Did you

try firing the boiler with the vent removed, to see if air comes out the pipe? The steam pushes air ahead of it, looking for an exit (higher pressure to lower pressure) so if the pipe is open you should get air.

The only thing I can think of that would alter this scenario is if someone put monster vents on the radiators. What vents do you have on them?



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Mitch Berkson

I didn't fire it with the vents completely off. I will try doing that.

The radiators have conventional vents on them - mostly Vent-Rite #1 adjustable vents with a few Heat-Timer VariValves.

Thanks for the help.

Steamhead

If those Vari-Valves

are wide open, each will vent as much air as a Gorton #1 main vent. This may explain the situation. You want the big vents on the mains and the smaller ones on the radiators.

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Mitch Berkson

I agree that that explains what is happening. I removed the vent from the longer main and steam came out fine and at about the same time it arrived at the end of the shorter main with vent still on.

I think what I could do to make the best of the 1/4" main vent pipes is to replace the Dole #95's with a Gorton #D on the 85' branch and a Gorton #6 on the 25' branch (for a 3:1 ratio).

It would be better if the main vents were bigger. Would it be worth using a coupling on the 1/4" pipe so that I could install Gorton #1 and #2 instead?

Also is there some kind of table which compares the venting capacity of various valves? I know Gorton's site shows a comparison within their valves, but how does a Gorton #6 compare to a Dole #95?

Steamhead

Try this

put three or four Vari-Valves on the long main and one on the short main. Make sure there's nothing below them though, since these vents will not close against water. Drill and tap additional 1/8" pipe thread holes in the main as needed to mount the vents.

Get enough Vent-Rite, Hoffman or whatever brand of good adjustable vent is available in your area and put these on the radiators.

Watch how well it works.

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Mitch Berkson

Sounds reasonable, but a few questions.

What do you mean by making sure nothing is below them?

Should these be installed on the horizontal part of the main or the vertical part where the pipes for the existing main vents connect?

Why do you suggest Vari-Valves instead of a non-adjustable vent like Gorton D which would have the added benefit of closing against water?

What is the advantage of this configuration over using reducers and Gorton main vents?

The existing vents are pretty high up. If I drill and tap the main, the new vents will not be that high. Will this be a problem?