Steam vent question

jrc2905 · February 2003

I have a customer with a steam boiler that used to be a coal-fired system. At the end of the main feed line there is some sort of what I believe is a relief valve. It is constantly venting when the system is running, the system pressure is 0 psi, so I am assuming it is stuck open due to the system being filled with water due to a failed auto-filled. My plan is to remove and plug this valve, because the new boiler has a high pressure cut out system.
But I do not see a lot of steam,so would this be correct?

I have since been informed that this would be incorrect, should this vent be open all the time? I thought you need 2-3 psi on steam.
It has been sugggested that I get a book on steam, "the lost art of steam" it seems a good investment considering that I see almost no steam systems out there.

steve_6 · February 2003

pictures

can you post some pictures of the system?

[Deleted User] · February 2003

Leo was

correct. DO NOT plug the hole. Remove the old vent and find and install a new vent.

Suggested vents: Gorton #2, Hoffman #75. If it is a small house, you might be able to do the job w/ a Gorton #1. But, this is one time when big is better. The larger the hole in the end of the vent, the better.

If you plug that hole, the steam main will not vent cold air on the start. Then the radiator vents will have to do triple duty. Slow, slow, slow.

Also, if the old vent is screwed directly into the steam main, raise it on a long nipple or 2. That will increase the life of the new vent.

Good luck.

jrc2905 · February 2003

What about the preasure on the system, it is now 0 psi, what should it be, this vent, vents constantly.

MikeC_2 · February 2003

steam vent

When all the air is purged from the system,the vent should close and pressure can build up.However sometimes the thermostat satisfies before any readable pressure is noticed at the gauge.

Steamhead · February 2003

\"Venting Constantly\"

could mean several things. If the vent is too small, it could be still venting air after the boiler has run awhile. If steam is coming out of the vent, it is worn out and needs to be replaced. If water is coming out, the system is overfilled or the return line is plugged causing water to back up into the main. The system will bang also if overfilled or if the return is plugged.

You should set the pressure switch ("Pressuretrol") as low as it will go. If it's the usual Honeywell PA404 (small gray box) turn the power off, remove the cover and rotate the small white wheel until the "1" points to the front of the control. Then turn the screw on the top until the scale pointer on the front is at 0.5 PSI. The burner will now stop at 1-1/2 PSI and restart at 1/2 PSI. This is correct for one-pipe steam.

To see if the vent on the main is the right size, measure the length and diameter of the main, and the make and model of the vent on it. Post the information here. If there is more than one main, post the information for them all. Vents are made in different capacities, and must be sized to vent the air in the main in about a minute. This way, steam rises to all the radiators at the same time, saving fuel and increasing comfort.

The sequence of operation is this:

1. Thermostat calls for heat, starting burner on boiler.

2. Boiler heats up until water boils. This usually takes about 5 minutes on a newer boiler, longer on older ones.

3. Steam moves from boiler into piping system. Main vents release the air in the steam mains. This step takes about a minute.

4. Main vents close when steam reaches them. Steam is now available at all radiator takeoffs, and begins to move toward the radiators.

5. Steam enters radiators at about the same time and warms the rooms. The gauge on the boiler usually does not move up to this point.

6. If the pressure in the system rises to 1-1/2 PSI, the Pressuretrol will stop the burner. The burner will restart when the pressure drops to 1/2 PSI.

7. If the water level in the boiler drops too low, the low-water cutoff will stop the burner. It may also call in a feeder to restore the water level. If the boiler has a float-type LWCO (such as McDonnell & Miller 47-2 or 67), the owner must flush it out once a week to keep sediment from building up. This can cause the float to stick and not drop when needed, which could lead to a cracked boiler. I like to flush these with the burner running- this proves that the burner will stop when the float chamber empties.

If you're not that familiar with steam, get a copy of Dan's "The Lost Art of Steam Heating". You can order it on the Books and More page of this site. It's very well written, covers all of the above and much, much more.

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David_4 · February 2003

Air Vents

Hello Anyone!

I have a one pipe steam system which has no air vents on the main lines.

I read various articles by Dan and others but it is unclear exactly where the air vents should be installed, what size and how many. My furnace cycles too frequently and my pressure reads 2.5lbs before cut off.

Thanks in advance.

Steamhead · February 2003

Install them

about a foot before the ends of the mains, but after the last radiator takeoffs.

How long are thre mains, and what size pipe is used? This will tell us what vents you need.

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David_4 · February 2003

Thanks a lot.

The mains pipes are 3" dia. I have three floors in the house, but not all the take-offs are visible. However, after one of the take-off, the main goes horizontally for abot 3' and then down vertically to become the return back into the boiler. There is a 4" tall nipple at the joint where the main is joined to the vertical return. The nipple is simply capped.

Could this be where the air vent was originally, because this appears to be the last take-off?

All visible take-offs are 2" dia. The house is approx 2100 sq ft.

Thanks in advance!

Mark A. Custis · February 2003

Sounds to me like

you found where the vent was. Try starting there.

Good Luck,

Mark

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Steamhead · February 2003

Pipe sizes

is that 3-inches the outside diameter or the inside? If outside, they're 2-1/2" inside. In order to tell you what vent you need, we also need the length from the boiler to the end of the main. That way, we know how much air we have to vent.

That capped nipple is where the vent was. Is that the only steam main in the house?

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Steamhead · February 2003

The answer

David has 40 feet of 3-inch pipe. The proper vent is a Gorton #2.

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steve_6 · February 2003

vents

Only one???

Steamhead · February 2003

Believe it or not

it contained just under 3 cubic feet of air. The Gorton #2 will vent about 5 Cu. Ft. per minute at 2 ounces pressure. So it has plenty of capacity.

You could use several Hoffman #75 vents to do the same thing. But since a single Gorton #2 costs about the same as a Hoffman #75, the choice is obvious.

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David_4 · February 2003

Air Vent

Hi Folks,

Just bought the Gorton # 2 for $52. Need to buy a coupler for the 1" dia nipple as the Gorton has a 1/2" inlet. The nipple is 10" long and I will not be using a Y-strainer.

Please stay tuned. I will inform everyone how the above arrangement works out.

Thanks!

Steam vent question

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