Water shoting from vents on 2 pipe steam

Scudrunner

I'm getting water out of the vents here. At first thought it was a bad trap pressurizing the dry return. After some research I'm thinking of lowering the pressuretrol (right now it is on .5 and off at 2) and checking the header piping. The picture is the end of the mains, there are two loops of a steam main and a dry return, the bottom horizontal pipe is a wet return but the water line is about middle of the pipe. Only getting water out of the vents on the right side loop, have not seen anything from the left yet. The both steam main and dry returns have vents at the end where they drop down, the steam to F & T traps and then there are vents on the outlet side of the F & T traps, the dry return just goes straight into the wet return which all gravity flow no pump. It was short cycling but I added vents to the dry return mains that where capped off, it is better now. Questions, are the vents ok at the F & T traps and any thoughts on stopping the water coming from the vents? Thanks.

BobC

Exactly which vent is spraying water?

Bob

Jamie Hall

If the "wet" return is only half full, more or less, of water, it is going to allow steam to go where it shouldn't, which can cause all manner of odd problems. Any chance of lowering it?

JUGHNE

My best guess would be that your wet return is getting plugged and not moving the water away from the traps. Have you ever open the 1 1/4"/1 1/2" sediment drip leg? If not, it is time to look inside. These could be full to half way up into the tee and now sludge is into the traps. Guessing by the age of the wet return it has not been opened either. Your "middle of the pipe" water line has probably risen closer to the top of the pipe and now the wet return air which was previously going down and up to the trap vents can not get thru the water trap. I would as Jamie says lower it and once you open it up you will probably want to just replace it. I would put in new laying on bricks on the floor with clean out ball valve port on each end.

I wonder if you really need the traps with a wet return. I hope some more enlighten steam people will look at this picture than myself.
So this is the complete return system; 2 end of steam drips (traps) and 2 dry return drops into the wet return. I'll venture to say the traps were added not that long ago to attempt to fix some other problem, maybe bad rad traps.
My guess is that the steam main would not have had any venting and relied upon the air going thru the radiators into the dry returns to be vented there. Some KH removed the dry return traps and plugged them and fixed everything by adding the F&T traps.

I guess I would drop the wet return, remove the traps, use the 3/4" drip lines into the wet return leaving a tee for venting the steam mains. Then add more venting on the dry returns above. Add a test port in the dry return drop lines to see if any steam shows up indicating which half of the system you have bad rad traps in.
Could you post pictures following this wet return to the boiler to where it connects to the boiler. Boiler pictures are good also.

Please someone else tell me if I am way off base here, this is just IMO.

Jamie Hall

@JUGHNE -- I should tell you if you're off base? Eek. But seems to me your spot on...

JUGHNE

Thanks Jamie, still want to see the pictures though. After all as my wife says "he is looking at his boiler porno site again".

Scudrunner

Bob, the steam main vent and the vent at the outlet of the F & T trap both on the right side of the picture. My next move I was going to do was to open the union on the outlet of the F & T to see what I'm getting out of it. The boiler is about 3 years old and I think it should been sitting up 4-6 inches higher to get the wet return completely wet. I'll get a picture of the header but do think there is an issue with that too because it is not 24" above the boiler and whoever installed it came off one side tap and thinking it should have been off both taps but I'm going to google the installation manual to see what the manufacture calls for.

I will check for the slug and clean that return and see what happens. Thanks for the help and will get back to ya's.

BobC

Can the returns be lowered below the boiler waterline? Do any returns join together above the waterline?

Not having the 24" is not good but it doesn't cause vents to fountain. Any pipes that aren't sloped correctly could contribute to the problem.

Bob

Dave in QCA

Dimension "B" Issue

I had to look at this drawing and zoom in to see the vents that are lurking in the darkness. The problems you are having are directly related to Dimension B considerations. If you have Dan's book, The Lost Art of Steam Heating, you need to read that section. If you don't have it, it would be a great investment for you!

First, this system appears to have been designed to drain into a condensate receiver and pump. The F&T traps on the ends of the steam mains, which look like they have been there from the beginning of time, are the dead giveaway. If it were a wet return, they are not needed.

Other observations: The end of steam mains are both vented up high and the vent lines rise up out of the elbows at the end of the mains. This is NOT a good location to mount a vent, but the installer protected the vents from condensation splash by installing them on enlarge surge chambers. Nice! The condensate lines are also vented at the point where they drop. This is just extra precaution to provide good venting to the radiators in the event that the horizontal condensate line below is slugged with water. If it was connected to a vented condensate tank, venting would take place there as well, but the four original vents would assist with ample venting and improve the system. Someone has added vents right after the F&T traps, and those DO NOT belong there and MUST be removed.

Now, the DIMENSION "B" ISSUE--- Dimension B states that that the water level in the condensate return lines of a 2-PIPE Gravity Return System will rise 30" above the normal boiler water line for every pound of pressure in the boiler. Thus, you know that when the boiler is off, that horizontal condensate line is half full of water. BUT, you must realize that when the boiler is running and pressure begins to build, that water line is going to rise in the returns. Remember, the horizontal line is connected directly to the boiler and will have the same pressure as the boiler. BUT, your condensate return lines are vented to atmosphere and have NO PRESSURE at all. So, the boiler water is going to back out, and up into the return piping, creating a water column equal to the boiler pressure. 1 PSI=28" H2O column.

So, to return condensate in a 2-pipe system, you must have one of the following: 1. A vented condensate receiver and pump. 2. I working return trap. OR, 3. A vaporstat set low enough to control boiler pressure and keep the Dimension B under control. Just from guessing the heights you are working with, I'm guessing that limiting boiler pressure at 1 PSI would work. If your system can run on 8 oz, that's even better. 8 oz boiler pressure would only back up the condensate 15" above the normal water line.

However, you have to get rid of those vents that are on the outlet side of the F&T traps. Those DON'T belong there. If we were dropping into a very low wet return line, the F&T trap would not be needed either, but as it is, you are essentially dripping the steam main into the condensate return piping above the water line, and you have to be able to keep the steam out. The F&T will do that just fine, but at this location, they cannot be depended on for adequately venting the steam main, but you have vents at the end of mains anyway. You also have vents on each of condensate return lines.

SO, in summary. Remove those new shiny vents mounted down low by the F&T traps. Install a vaporstat (low cost) to control the boiler pressure so that you can return condensate by gravity, OR, install a vented condensate tank and pump (high cost) to return the condensate against the boiler pressure. If you find your condensate return lines are getting hot, and if steam is getting to the vents on the return side, you have a bad radiator trap somewhere in the system and that must be repaired because it will interfere with even steam distribution.

Hope this is helpful.

Dave in QCA

I failed to mention that yes, it certainly is possible that the low horizontal return line may be full of muck and causing a back up. It would be a good idea to flush it out. But, Dimension B is absolutely a problem here and you've got to make some corrections to deal with those laws of physics.