Conversion to one-pipe system

Michael_5

I have to immediately say that I am not a "wethead", just a homeowner with the boiler... I had a one-pipe system where the condensate returns to a boiler via a separate pipe. This pipe was going through the center of the basement, so I decided to convert the system to a true one-pipe, where the condensate and steam will use the same pipe. The contractor that I used invited a specialist from the boiler company who said that this is not a problem. And the job had been done by a heating contractor with no prior experience with the boilers:(. Now, I have the system that does not work. When they (contractor) got rid of the air from the system, it worked perfectly, but then - "bang, bang, bang!!!!". They are blaming the heat exchanger in the boiler (American Standard, probably 40 years old). It has a tiny crack. But the system worked before! The questions are:
1. Is it possible to use the boiler with the tiny crack in the heat exchanger?
2. How can I calculate or find out the proper sizing for the pipes?
3. They (contractors) did not change the levels on the existing pipes). Do they have to change it? (according to this site they should)

Mark Walnicki

Should've left it

as it was, I'm thinking. You can set up the piping to the system as you envision (which is only one of a few "true" one pipe systems) but at what expense, with removing the existing piping, installing new larger piping (at the proper pitch), and insulating that piping? Might want to look into reinstalling those returns.

The crack in the boiler is not to blame. I would keep an eye on it, and start researching your boiler replacement options now. Try the 'find a contractor' feature, maybe someone is near you that could get to the bottom of things. "Lost Art of Steam Heating" & "Golden Rules" would be good additions to your library.

Steamhead

Reroute the return

so it won't be in the way. Your system will never run properly without the return unless you do some major surgery. If it keeps banging, that tiny crack in the boiler will grow quickly!

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Michael_5

Thank you, Mark and SteamHead, for your responses. The contractor who did the job actually invited an expert from the local boiler company to look into the proposed solution (conversion to the true one-pipe system). And he approved it! Now I am stuck with the boiler with the suddenly discovered tiny crack and the piping that does not do the job. Now I don't really know whom to trust in my location to properly do the job.
The questions are:
1. Should I replace the entire system (boiler and piping)
2. If yes, how much it might cost and how can I find the correct contractor
3. How I can be sure that he/she will do a correct sizing of the equipment?
3. If no, then is it possible to route the returns alongside the steam pipes?

Steamhead

No Need

to replace the entire system. You can use a dry return but be sure to pitch it back from the end of the steam main toward the boiler 1-inch in 20-feet, and drop it to the floor near the boiler before going into the Hartford Loop. This will insure that the water will flow out of the steam main and back to the boiler by gravity.

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Michael_5

I am not looking to get a free consultation, but I already asked for advice and paid one local expert from the boiler company and the result is that I have a ruined system. I was searching for a contractor on this website but for my zip code (40206) it is not available. I am in desperate need for an expert advice here.
Please see the attached picture. I had one-pipe parallel flow system where the steam was going from the red arrow (see picture) through the middle of the basement to the radiators. What they did: removed the steam line, added new pipe (blue arrow) that connected the steam (red arrow) to the return. The idea was to create one-pipe counter flow system.
The diameter of a return and new pipe are approximately 3 inches.

I would really appreciate it if someone can consult me of how to restore the system or make it work.

Steamhead

The obvious problem

is the return from the new counterflow main (pipe #2). It is hooked into the end of the other steam main (pipe #3) above the water line which is a no-no. Steam is rushing into pipe #3 and traveling up the other steam main the wrong way, which I'll bet is what's causing the banging.

You must drop return #2 below the waterline and tie it into the bottom of the U-shaped pipe before the Hartford Loop. The water in the U will keep the steam from jumping into the other main.

The counterflow main should have a properly-sized main vent at its end, just like a parallel-flow main would have.

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Michael_5

Dear SteamHead,

Thank you for the reply. My understanding of the piping was a little different though. Pipe #3 is now a main line. It carries the steam to the radiators and also the condensate from the radiator back into boiler. Picture shows that pipe # 3 goes into the Loop (at least that is how I undestand it :-) ). The pipe #2 is carrying the steam to the pipe #3. Contractor added the pipe # 2 and connected it to the pipe #1 which was previously a steam line. So, it looks to me that the water can return back to the boiler directly via #2.

If it is correct, then I don’t understand the solution that you proposed. How the steam is supposed to get to the pipe# 3 then? I have attached detailed picture of how #2 is connected to #1.

I really appreciate your advice.

Steamhead

How did the steam

get into main #3 before the change? Also, where does the second takeoff from the header (the one that comes up in back of pipe #1) go to? And what's on the other end of the tee that pipe #1 feeds into (which is a "bullheaded"tee, a big no-no)?

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Michael_5

Dear SteamHead,

I have created four schematic drawings to illustrate how the system used to be and what it is now. They are:
"Original pipes layout" - shows how pipes were set up before.
"Original boiler view" - shows pipe schematics around the boiler how it used to be.
"New pipes layout" - shows new, non-working system.
"New boiler view" - shows pipe schematics around the boiler now.

My contractor claims that the system does not work because of the tiny crack in the heat-exchanger. It appears that this crack exist before the pipes were changed.

I really appreciate your help.

Michael_5

If you would need the actual pictures, I will be glad to just make pictures of every major node in the system.

Steamhead

Nice Diagrams!

I see the trouble now. The steam lines were sized to be parallel-flow, fed thru the single steam main off the boiler that was removed. If you're running them counterflow, they have to be one size bigger so the condensate can flow back against the steam, and also they need more pitch- 1 inch in 10 feet- back toward the boiler. This is covered in Dan's book "The Lost Art of Steam Heating".

I'm assuming the original steam line from the boiler was cutting into the available headroom, and that's why it was removed. Your contractor ought to find a way to re-install that pipe so it doesn't hang so low. Maybe it could run counterflow, pitching up to the center of the basement, and parallel-flow (downhill) from there to tie into the two steam mains.

The alternative would be to repipe the present counterflow mains with increased pipe size and pitch. If you do this, you will also have to move the main vents to the ends of the mains.

Going to Wetstock, so I'll be off the Wall for a few days.



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Michael_5

Dear SteamHead,
Thank you for all your help. Remaining questions are:
Are there any problems with having one-pipe counterflow system compare to parallel flow system?
I don't know anything about "proper size" of the pipes. My guess is that this boiler is in the house for the last 50 years and two radiators had been removed. Assuming that I have 6 radiators - may be the current pipes size is enougth?
Where I can find:
Methods of calculating the pipe sizes for such system based on the # of radiators?
The level of pressure for such system
Do I have to ask the contractor to insolate the pipes in the singlepipe counterflow system?

With great respect,

Michael