One-pipe steam, advice on main vent size & placement

David_52

Hi everyone! Having observed my system this winter, I am now taking the first step recommended by several helpful folks on the Wall- that of evaluating the venting needs of the mains. In doing so, I’m hoping that some Wallies might be willing to offer advice on main vent size and placement. Attached is a diagram of the system depicting pipe diameters/lengths, radiator information, and vent information. I like the “maximum venting” idea utilized by Gill and have seen that website and e-booklet. There aren’t a lot of main vents presently on my system right now, which is my primary question- am I correct in thinking that the existing vents are not adequate and, if not, where should new ones ideally be placed? Also, and more specifically, I’d like to solve what I perceive to be a problem in how long it takes for steam to arrive at various radiators. Those times are also noted on the attached system diagram, some taking 20-30 minutes to even begin to get warm. Overall, my system usually cycles for well over an hour- averaging about 70-75 minutes from when it kicks on at about 61-62 degrees and until it shuts off at about 65-67 degrees.

On the system diagram, this is very idiosyncratic to me- hope it makes sense to you! If not, please ask questions.

Thanks for the advice and time; it’s much appreciated!!

Sincerely,
David

nicholas bonham-carter

system venting

i think you need at least 1 gorton #2 for each dry return, if not several. i have 3 on each of 6 dry returns [on manifolds where they drop down to become wet returns]. maybe that is overkill however it will keep the escaping air velocity down to the point where debris is unlikely to be blown into the vent, and if 1 vent becomes plugged, the other 2 can still do the job.

my system is 56 rads, 1,050,000 btu with longer runs, but still takes less time for the steam to "arrive" at each rad. in fact my air is out before the pressure hits 3 oz, which leads me to believe that low pressure + ample venting + new boiler has dropped my gas use in cu. ft. 25%!

like you i have three floors. the third floor has the higher capacity rad-vents, and all the others are the same original hoffman bullets. i want my horizontal mains to be full of steam, before the steam starts to fill the risers, so that all rads have steam at the same time [or close to it]. low backpressure with multiple main vents helps these mains fill quickly, and i am not paying the gas co. to get the air out through constipated little rad-vents as i once was. when you are timing the arrival of steam, use the temperature of the rad instead of the room, to start with.

when you make up a list of parts you need, don't forget to find a good low pressure gauge [0-15 oz. gaugestore.com on the same pigtail as your vaporstat] mine is set at 2-8 oz. you will not know what is happening without this gauge. if there is any water hammer in the system, then that also is wasted energy.--nbc

David_52

vent at dry return, not end of main?

Thanks nbc for the advice- are you suggesting placing the vents at the ends of the dry returns and not at the ends of the mains? In Lost Art I thought I remembered reading something about not venting dry returns- what are your thoughts on that?

Thanks again! David

nicholas bonham-carter

vent placement

i would always try to vent the whole main [at the end of the dry return] so you can see if one main is filling with steam more slowly than the others [more venting needed]. if the air is still in the dry return, i feel it is a wildcard in the system, perhaps able to interfere with the condensate return. also to consider is the clearance between ceiling height and pipe height should be greater at the point of drop to the wet return, than at the end of main.--nbc

Unknown

Hi David- I recognized the diagram and I believe we chatted together last winter. I see you've done a lot of work on layout /timing which gives you a much better idea of how well your system is working. Your times seem fairly reasonable except for Branch #4.

Generally speaking a standard (parallel flow) main becomes a "dry return" just after the last radiator lateral. As the main is usually sized down at this point, as it is just carrying condensate, it is advantageous to place the main vent on the larger main pipe, however venting on the dry return will basically accomplish the same thing. The only down side on this would be if the dry return was very undersized. I agree with NBC - get the air out of there!

As I remember it, a lot of your mains were counterflow(?)
In a counterflow main, the main vent should be located at the end (the high point of the main) past the last radiator lateral.

As you have you initial system timing down- I'd now experiment and see what times I could improve with the existing main vent placement. As the maximum venting possible is an open pipe. I'd remove each main vent individually and time just how long it took to get steam to the vent hole. I remove the vent and attach a temporary setup using some pipe nipples (and elbows) and a full flow ball valve. The idea is, using the ball valve, to be able to close the vent when steam reaches it and arrange the nipple (and elbows-if necessary)to be able to vent the steam in a safe direction. BE VERY CAREFUL! Steam can give you a very bad burn!

Since an open vent hole represents the maximum venting available, you then match the vents (maybe several necessary to achieve this) to the venting capacity of the open vent hole. The only way this can be further improved is by enlarging the existing vent hole in the main or adding an additional vent hole (plus vents) to the main.

I also use a similar setup to check my radiator timing IE: 1/8 ball valve and nipple/elbow setup. (If I want to check the pressure here, I also attach a gauge on a tee between the nipple coming out of the radiator and the ball valve.)

I don't remember exactly what you said about your system. If it is as in your diagram, I'd be concerned about the "Bullheaded tee" connecting "A" and "B" and also your opposed steam risers coming out of the boiler. These are a big design "NO-NO" and have to be costing you efficiency. How much I have no idea. Maybe one of the steam pros on here might have a better idea. You might want to have a steam pro fix this for you and at the same time give you some ideas on your system re: venting etc.

I'd also think about insulating the mains(and near boiler piping) if it hasn't been already been done, and make sure your thermostat is one that has adjustable cycle function.
As energy prices are now again rising, fine tuning the efficiency becomes more important than ever.

- Rod

David_52

Hey Rod- yep, that was me and I appreciated the help a lot. Thanks for the input on vent placement with respect to parallel and counterflow situations. My mains are a mix of parallel and counterflow: #1 is parallel until the Gorton vent, after which is becomes counterflow. #2 is parallel all of the way and the vent is actually pretty well situated given your feedback. #3 is strange because it has a wet return that would seem to indicate parallel but is physically situated in such a way that it seems like counterflow (it is lowest at the boiler and highest by the takeoff for the first rad- also where the wet return begins...). #4 is truly bizarre- the dry return seems to serve only the last two rads but the whole main looks to be physically situated for parallel flow. Thinking about it now, this is likely the source of a lot of problems on that line as well as some wicked water hammer.

I like the idea of experimenting with an open line, but wonder about the utility of that if the vents might need to be moved- if vents are not currently in the right places, it would just be wasted time, I think, to experiment with what's there. To my eye, the #2 main is the only one that is well-placed- though #1 may also be pretty good. #3 doesn't even have a vent to experiment with, and #4, well, I'm confused about that one. I will head down there this afternoon and take the advice that someone gave in the winter- assessing the pitch of those pipes by placing signs with arrows pointing in the direction of flow...

Thanks again for the advice; it's much appreciated. David

Unknown

Hi David- What ever you do I'd only make one change at a time and see what effect it has on your system. If you change multiple items at the same time and it has an adverse effect you won't know which change caused it.

On older steam systems I think it helps to try an visualize
what it was like when it was originally installed and then try to figure out what "additions" were done over the years.
It's usually these "additions" that cause most of the problems.

Since you've now read "The Lost Art..." you probably have a pretty good idea of what needs to be done to normalize your system. It may not be something you want to tackle right away but the opposed steam risers have to be producing a lot of wet steam and costing you money with inefficiency so I would make that a high priority and while it probably isn't as bad, fix the "Bullheaded Tee" at the same time.

You have a lot of Gorton #1 s and Gorton D s in your system.
The Gorton D and the Gorton #1 both have the same venting capacity. The Gorton # 2 has 3 times the venting capacity of a #1 or a "D". Maybe the place to start would be to get a couple of #2 s and change them out one at a time with the #1 s or the "D" and see how that affects the system.
I'm a bit afraid that with the bullheaded tee if you put too much venting on one branch it may starve an other branch so experimenting a bit first before drilling and installing new vents might be beneficial.

The only benefit the "Open pipe test system" has is that it shows you what the maximum venting performance that can be obtained for that individual vent hole. (with out enlarging it or drilling a second vent hole)

You mentioned that you were checking slope. In an old house you especially want to check for sagging in the line as this causes water hammer. (some of my mains looked like hammocks!) This I found is hard to do if there is insulation on the pipes. You can try using a torpedo level. A string line level works well too. I use a series of nails long enough to touch the pipe and protrude through the insulation which then makes it easy to see how well the nail heads align with the string. Remember minimum pitch on a parallel flow main should be 1 inch in 20 ft and on a counter flow main - 1 inch in 10 ft.

- Rod

David_52

\"opposed risers\"

Thanks again for the feedback- on the note about "opposed risers", do you mean the two branches that come off of the header and serve the four mains? I'm definitely aware of the problems with the "bullheaded tee"- but want to make sure that you're not JUST referring to that but to an additional problem in that same area. Thanks! David

David_52

How to fix this?

Speaking of checking slope, I did that and came up with one very clear problem area- which corresponds to timing problems and water hammer noises. In the attached picture, which is of part of main #4 in my diagram, you can see the take-off for the "HALL" rad in the upper left, the supply to and dry return from "DINING (small)", and arrows showing the direction in which condensate would flow given the pitch of the pipe... clearly they all coalesce around a problem area. To be clear, the top layer of pipes is the steam supply from the main and the bottom layer is the dry return.

It looks like there may have been a different arrangement here at some point given the unpainted caps, but what I'm wondering is how to fix it! Any thoughts from anyone? Thanks! David

Unknown

Hi David- In your diagram and if my memory serves me correctly, from pictures you posted last winter, the risers exiting your boiler connect to the header on both sides of a single riser leading up to the mains. This is considered a BIG "NO-NO" as the steam streams oppose each other. This is discussed on page 51-55 of Dan's book "The Lost Art of ..."

As you can see in the attached drawing "Opposed Steam streams" the steam streams "Z" and "Y" collide at Point "X". The Steam stream "Z" also collides with the Condensate stream flowing towards the equalizer.

In the second drawing, "Normal header configuration", both steam streams and condensate stream all travel in the same direction so therefore it is much less likely that the condensate will be splashed up in the steam stream and carried into the mains causing "wet steam"

The attached picture, "Skim Port", is a good example of the proper piping configuration of a boiler similar to yours. Note it also has two separate takeoffs to the mains. This is beautiful work and was done by one of the pros on this site. I'm afraid I didn't take note of his name so as to credit him properly. Note the skim port/ ball valve coming off one of the boiler risers.

Just took a look at your picture of the hall/small dining room piping. If I'm seeing this right, the msin is connected to the return before reaching the hall/dining room radiators? How are the two pipes connected on the dining room end? Looks like someone was tryin to setup a drip. I still think you'd be advised to have a steam pro look at your system. The phrase "one look is worth a thousand words" comes to mine and a steam pro would have a far better idea of what fix to apply.

- Rod

Unknown

Hi David-
I took another look at your piping picture and on blowing it up, can now see that the fittings at # 1 are NOT connected. In my previous post after a quick first look I thought they were connected, thereby "short circuiting " the main.

As to your slope problems- Is it possible to raise pipe "B" so the slope flows towards the Dining room? (in the direction of the red arrow) This could be done by either raising or lowing the appropriate end or a bit of both. The object here is to turn it into a normal parallel flow main. At the same time could anything be done to improve the slope of the dry return?

Another possibility - You might be able to add a drip (#3) between the tee (#2) and the dry return. This(#3) needs to be 5 ft.long (per`page 88 of "The Lost Art...") I keep referring to "The Lost Art.." and just realized that I haven't asked you if you have a copy.

Disregard numbers 4 / 5. I put them in picture and then decided not to use them.

I hope I'm being of help to you but I'm very much afraid that since I can only see just a small part of the picture I might be leading you down the wrong path where as a steam pro inspecting it would immediately see what is possible and what isn't. I know I keep reiterating this as I'm a great believer in defining what items are viable to be done personally with regard to proper tools and experience and what are best left to a experienced pro.

- Rod

David_52

Thanks Rod... any information is good information! I think the drip may be the way to go for that specific problem. And, I found out today that a co-worker's husband owns a large plumbing supply business here and has an employee who is an old steam guy- so I'll be able to consult with him soon. All of this discussion is so helpful, though, and I appreciate your time.