Help with Steam Boiler Main Vent Sizing

mcvetyty

KC_Jones, thanks so much for your input, and I hope I am not wearing everyone out with these questions. I really appreciate the help.

In order to explain the situation better, I threw together a diagram. The black lines are the main/returns, the yellow lines are the current main vent locations, and the red lines are the risers going up to the radiators. The long red line is the one in question, and the one illustrated in my previous post. Based on your last comment, I am not sure if my terminology is right. It seems to me, that all of my risers are linked to the main returns, but is that a mistake to call them that? And then is this setup an issue where the longer red riser should be connected sooner on the main?

Thanks again.

KC_Jones

That is a dry return which means that it does have steam in it, but in addition at that location it also has ALL the condensate from the 5 other radiators on that line in addition to the condensate being created in that pipe as the steam moves along. So that would possibly be choking down on the amount of steam that can get to the radiator. Without being there it's hard to say for sure what the best solution it, but I would say moving it down the pipe any amount would help. At a minimum I would agree with what was already stated, before that main vent for sure.

mcvetyty

OK, those are great points, and I'll bring them up with them during my next conversation. One alternate fix that I was considering is to sever that problem riser from its current location and hook it up directly to the main coming out of the boiler with a T. Would that be a valid solution, or would that be a mistake to do?

KC_Jones

If you are talking about the boiler riser or header, that isn't a good idea either. You want it on the main. On the riser or header you would be introducing additional condensate into a place you want as little water as possible. Remember you want dry steam coming out of that boiler.

mcvetyty

Ah yes, of course. Great point. Ok, thank you again for all of your help!

Captain Who

mcvetyty said:

Ok guys, I am back with results I am not so inspired by... I did the test that Abracadabra recommended (basically attached a ball valve to return #2 to see how fast the main return heated up). The positive news is that the nipple is actually 3/4" and not 1/2. The not-so-positive news is that with a 3/4" ball valve attached, the pipe only heated up 6 minutes faster than it did with the Hoffman 4A on it.

The time-to-heat with the Hoffman 4A was 17:31, and the time to heat with the opened ball valve was 11:31.

So, if I understand this correct, even if I invest a ton in Gorton #2 valves, the most I'd get is a six minute gain. Is that accurate?

Does this mean my dream of getting heat to all radiators in less than 10 minutes is probably never going to be realized? Any options?

It might not be as bad as all that. Remember that your vents are at the end of the dry returns instead of at the end of the mains. You ought to also do the test where you check how long it takes for the end of the main (before it loops into the dry return) to start to heat up.

I have a similar situation on my install........where the only vents are at the ends of the dry returns. I want to move them to the beginning of the dry returns. That way I can begin to make pressure sooner and hit the cut-out on the pressuretrol sooner when recovering from the overnight setback on the thermostat.

mcvetyty

I'm back, and perhaps more confused than ever. I'm trying to understand my system, and based on KC_Jones previous comment, am I correct in describing components in the diagram attached as: the middle black line is my "MAIN" and then after the T on the middle left, the black lines should be referred to as "Dry Returns?"

If that is the case, then do I actually want the two vents (yellow lines) to be where they are, or should one be added to just before the T (which is the end of the MAIN)?

Finally, is it a mistake to increase the current venting as much as I plan to (I am working on adding multiple Gorton #2's at each of the yellow lines), since that will just be pulling steam through the entire Dry Return pipes? Or is that still a valid course of action since each of the radiators actually rise up from the dry returns themselves?

KC_Jones

I am sure I will be corrected if I am wrong, but the dry return is technically after the last radiator takeoff so in your diagram any place a radiator is connected is still considered your main. Your set up is definitely outside the norm, but with steam what is truly normal?

Fred

What KC says is correct. If there are radiator runs off of the Main line that the Boiler feeds steam through, that is a part of the Main. After the last radiator run, you begin the returns that should drop down at some point and feed back to the boiler. When they drop below the waterline of the boiler, they are considered Wet Returns. Until that drop, they are Dry Returns. You can't put a radiator run on a dry return and expect it to get suffectient steam to feed a radiator. With the condensation running back through those dry returns, any steam that might have gotten to that run would be condensed by that water. That radiator is acting like a large vent on that return but again, the condensed water collapses the steam before it could get to that radiator.

From your diagram, I can't tell if you are trying to put your vents at the beginning of the Mains (which you do not want to do) or at the end of the Dry returns. We need to know which of those pipes come off of the top of the boiler and which way the steam flows. If those vents are at the end of the Mains (following the flow of the steam) you just need to make sure the vents are added after the last radiator. They do not have to be at the end of the returns but if thats the only place you have to add them then add enough venting to include the air in the additional piping.

mcvetyty

Thanks Fred. I've attached a more thorough diagram which hopefully helps clarify things. To be clear though, I don't have separate returns. The main Tees off and loops around the basement, and the red lines indicate risers going up to the radiators (one-pipe radiators), and then after the two feed all of the radiators, the two ends drop down into the hartford loop after the vents. There aren't separate pipes for the returns - it's all connected.

In other words, each red line is a pipe that connects directly from the main to a radiator, and that's it.

I assume both the steam, and condensate just travel in the same pipe throughout the entire system and because all of the pipes are pitched ever so slightly it all just makes its way to the very end and drops into the hartford loop.

So assuming my explanation makes sense, I don't necessarily know that I have what would be called a true 'dry return' - I think I have a main, that splits into two mains, that basically just ends up collecting and dumping all of the condensate back down to the boiler at their very end.

Captain Who

Your photo that shows the "one", "two", and "three" also shows a Tee. The confusing thing is that, in your schematic diagram, there is no corresponding Tee shown. As said above, you need to show the header on the schematic or at least put arrows showing direction of steam flow. Also, the photo is very dark so it is hard for people to see where the vents are or aren't and where that mystery riser attaches. It certainly looks to me also like the main problem may be that the riser is after the vent. Very strange to have such a long main and such a short dry return in the system. That main better be super insulated or it will be flooded with condensate by the time it is near the end with the last runner that leads to the problem radiator. It seems like a bad idea that the installer had to put a Tee in the supply main, especially without the pipe leading into the Tee being a larger diameter than the two pipes leading out. That has to cause a big drop in steam velocity there. I'm not sure what the effect of that is, but I have a feeling that it could cause a pressure increase which could cause condensate to form there. Hard to remember my Bernoulli Theorem knowledge at this point lol.

Captain Who

PS: With a Tee in the main like that, how can both outlet branches have downward pitch? Either one or the other can have downward pitch and the other would be upward.

Captain Who

Oh I see now your latest schematic clears some of that up, except for the Tee at the end, but you made that clearer with your explanation.

It's a very strange system.

mcvetyty

Captain Who said:

Your photo that shows the "one", "two", and "three" also shows a Tee.

Correct, that T is also on the diagram it's where the red riser meets the black main in the top right of the image.

Captain Who said:

It's a very strange system.

Captain Who

In the interest of having dry steam to the risers to the radiators, the supply main(s) is usually kept short as possible, ie. the boiler is located so as to facilitate that, and there would be two separate mains leaving the header which would eliminate that problematic Tee you have, and then you would have 180 deg loops leading to dry returns which are about the same length as the two mains, with all sloping downward from the boiler in the direction of steam and condensate flow. It is what it is I guess.

Trying to be constructive though I guess you have to move that last riser to before the vent and insulate the crap out of that long main, maybe with 2" fiberglass.

Fred

Even though the Main is looped back to the boiler return (Hartford loop), at the end of the last radiator connection it becomes your dry Return (it is a dry return until it drops below the boiler water line and then it is considered a wet return). The return water flows in the same direction as the steam and hence is called a "Parallel Flow" Single pipe steam system.
In any case, that one steam pipe and radiator needs to be moved to the portion of piping that is actually the Main, not at the end where it has become a part of the return. Once that pipe/radiator is moved, you can add your Vents anywhere after the last radiator run. If you have no other options, you can even reduce and/or bush that wrong radiator take-off down and put your vent antler there. just make sure you add enough vents to accommodate that addition run of pipe (from the last radiator to the new vent site)

mcvetyty

I've found the smoking gun! I looked through my email history and found a picture of the boiler installation in progress! I've attached it along with a side-by-side of the current configuration. When compared to the current setup, you will see two things:

1) You can see that originally that riser did NOT connect to the dry return it connects to now, and it seemed to have its own return back down to the hartford loop.
2) You can see that originally there must have been a pipe (there's a hole in the picture) that extended out towards us and must have connected to the main right above the header, or somewhere?

So, with that being said, I think I have enough to go back to the installer and illustrate that they mucked this radiator up and hopefully they'll fix it. The decision I have is whether I have them attach the riser to the end of the main, or have them put it back how it appears to have originally been, at the beginning the main. I assume the latter will be more work, but lead to much more heat in that room than I would get otherwise.

Thanks a lot for all of your help guys - I couldn't have done it without you!

Fred

Great! I'm glad you got it figured out!

KC_Jones

I would make them put it back the way it was. They undid something to save themselves some work in that situation I think they should learn not to try and cheap out on the install in the future. Also the way it comes off at a 45° angle is the way it should be for a radiator, that allows the condensate to flow along the bottom of the pipe.

nicholas bonham-carter

The "smoking gun" pictures look like too small a pipe caliber in the picture, for the install.--NBC

Fred

They probably were (those are his old original shots). The new piping looks like it is sized well (those pics are on page 1 with his original post)

mcvetyty

Success! The installer came out and after talking through what I've learned agreed that it was piped wrong and they are going to put it back to its original piping next week for free. Thanks again for everyone's input! I learned a lot through this process.

KC_Jones

Good on them for admitting a mistake and making it right. Sounds like at the minimum you have an honest contractor there and that is a good thing! Hopefully it helps and allows you to work out the venting to get that radiator working properly!

Fred

That is great! Best of luck getting it resolved.