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Two pipe system some cold Radiators

I just bought a home built in 1917.  It has two pipe oil fired steam.  The boiler is less than 6 months old.  The system has two loops; one (that is closer to the boiler) works fine and heats the radiators on on both floors in the front section of the home.  The other main runs 3/4 the length of the home (35-40 ft.)  On this second longer main none of the radiators heat up.  There are not any steam traps at the radiators, or vents.  I recently shut all the valves on the good loop and the steam did heat some of the rad on the long loop but not all. 

I am lost

Please look at the attached file, any info would be appreciated.


  • Rod
    Rod Posts: 2,067
    Two Pipe Steam System

    Hi - You said that you just bought the house and the boiler was less than 6 months old, does this mean you haven't any experience with the steam system before the boiler was replaced?  We need to know more about your steam system and the first thing that would help is if you could post some pictures of your new boiler and the piping attached to it. Take the pictures from back away so we can trace out the piping. (We can blow the pictures up if we need closer detail). Take the pictures from different angles so we can trace the around the boiler.

    You mentioned there are no steam traps on the radiators. It would be helpful if you included a picture of one of the radiators as it might help us to determine what variety of two pipe system you have. Also take a picture of any "weird contraption" that you see attached to the steam piping.  Attached below is diagram of two typical two pipe installations. There are a few variations of the two pipe system. You might check and see what your system has in common with the systems in the diagram.

    - Rod
  • Jamie Hall
    Jamie Hall Member Posts: 21,535
    I know I sound like a stuck record

    but it is not at all uncommon in two pipe steam systems to have a steam main -- of course -- and a dry return -- and a wet return.  And at the ends (or sometimes in between) of the steam main and the dry return there will be drops which go into the wet return.

    And it is equally common, when a boiler is replaced, for the water line to be lowered -- and for at least some of the wet return to become dry.  Which will let any steam pressure in the steam main go happily looping around and pressurize the dry return -- and prevent any heat at all from getting to the radiators, or at best only a little bit of heat.

    Look around your basement very very carefully and trace out all the heating lines to see if maybe, just maybe, you might have a problem like this...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Thanks So Much

    Here are some more pictures.  What I assume is the dry return runs parallel to the main?  It never gets hot at all, at any point in its run.  The wet return, that eventually runs across the floor back to the boiler gets very hot.  Hoter than any of the radiators on that loop.

    Here are some pictures of the plumbing.  Thanks again.
  • Mark N
    Mark N Member Posts: 1,094

    Your near boiler piping is screwed up. There is a bull headed Tee and I don't see an equalizer at the end of the header. Major piping mistakes. Also the pressuretrol is set to high Turn the cut-in down to 0.5 psi and set the wheel under the cover to 1.
  • Steamhead
    Steamhead Member Posts: 16,242
    It's some form of Orifice Vapor system

    see if you can find any of the original radiator shutoffs, take a pic of a few, getting both sides if you can, and post them. This may help us ID the system.

    The original rad shutoffs would have had orifices built into them, so as long as the boiler pressure didn't get above a certain point, the steam would not enter the dry returns. You can get disk orifices to fit the valves that have been replaced, and control the boiler pressure with a Vaporstat that cannot be set higher than 1 pound.

    If steam or air is rushing thru the rads faster than it should, it will pressurize the returns and stop the flow of steam to the other rads.

    Where are you located?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • MotownSteamer
    MotownSteamer Member Posts: 110
    edited December 2011
    I think I see the equalizer

    back there against the brick wall. It's not piped from the header, it's coming from that upper arrangement with the bullheaded tee.

    While the near boiler piping is a problem-and there are some opportunities to fix it without too much effort-I think we need to understand the venting a little better. I saw one picture with an end-of-main vent, and another picture of an old, cruddy vent. Figuring out where all the vents and whether they are working would be a good start.

    Also, the radiators have the unique ball check system instead of a trap. These need to be checked to see if they are functioning.

    From what I know (I'm still a novice) hot returns are indicative of condensate returning (a good thing) but if they are too hot it could mean steam has passed into the return.

    Vents. Look for them and let us know everything you can.

    The pressuretrol cut-in is too high; perhaps someone's attempt to overcome these problems.

    6 moth old boiler? That installer needs to come back and pipe it to spec!
  • Jamie Hall
    Jamie Hall Member Posts: 21,535
    Check the temperture of that wet return

    If it is getting steam hot, or nearly steam hot, then steam is getting into it; this should never ever happen (warm, perhaps; hot, no) even if steam is getting through the radiators (which it probably is -- next paragraph).  Check everywhere.  What you are looking for is anywhere where there is a drip from the steam main coming down.  The elevation of the wet return at any such drip must be above, and preferably several inches above, the elevation of the boiler water line.  It could be anywhere -- from right near the boiler to way off in a back corner somewhere.

    On pressure, this is surely some form of vapour system, in which case it should not operate at more than a pound, and probably no more than 8 to 12 OUNCES per square inch at the cutout.  Whatever else you do, you will need a vaporstat, not a pressuretrol, to control the system.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • College Hill

    I live on College Hill in Easton Pa. 

    Thanks for the information.
  • Rod
    Rod Posts: 2,067
    2 Pipe System

    Hi - It appears you have a 2 pipe vapor system which is  the “Cadillac” of the steam systems. Once you get the “bugs” straightened out, you will have a very nice system.

    As  others have mentioned there are problems with the piping configuration on the new boiler. This should be fairly easy to get straightened out. Since this is a vapor system you need to run it at very low pressure so you will need to use a vaporstat instead of a pressuretrol.  While Vaporstats do the same job as the Pressuretrols. Vaporstats work far better at low pressure than Pressuretrols.  A normal steam system runs at under 2 PSI and Vapor systems run at a much lower pressure.  The present pressuretrol can be used a safety high limit control to back up the vaporstat.

    I still don’t have your system quite  figured out. I’ve attached 2 of your pictures which I have blown up so to see the detial. There seems to be 3 returns that I have labeled  “Return “A”, Return “B” and  Return “C” . You mentioned you have only two mains so I’m not sure why there are 3 returns?    

         Each return should have a separate main vent. I’ve circled what I think are mains vents could you check and see if there are in fact main vents and to which return  do they belong?  Does the third  Return, (Return “B” or Return “C”)  have a main vent?  

    With reference to my earlier reply’s diagram, trace your steam mains to see if they are connected to the return pipe from the end of the steam main in which case they should have a trap on the connecting pipe or do they drop to the floor from the end of the steam main in which case there should be a main vent at the end of each steam main. Let us know what you find.

    There are some very good  books on steam systems available on this website . I would suggest you get the “Steamy Deal” which is 3 books. One is “We Got Steam Heat” which is a good introduction to residential steam heating and the second one is “The Lost Art of Steam Heating” which contains a lot of information on steam systems including vapor systems. The 3rd  book is on troubleshooting steam  systems. All these books are written so the homeowner new to steam heating can understand them. I’m a homeowner myself and these books are what most of us started out on. Here’s a link to these books in the Shop section:


    Let us know the make and model number of your boiler. It should be on a placard attached to the boiler.

    You’ve got some good advice from other posts already.  Pay particular attention to Steamhead’s replies as he is a very experienced steam pro and is an expert on vapor systems.  Let us know what questions you have and we’ll do our best to answer them.

    I’m also attaching an article on orifice systems which may be of help to you.

    - Rod
  • More info

    Thanks to all for the help.  Rod the books are on the way.  I am trying to work with the local HVAC co that did the work required for the sale.  I am going to give them a chance to resolve the issue, and they seem willing.  If they are able I will know soon enough.  Here is a diagram of the back of the boiler, where the returns are.  There are 2 returns for each Main. Both mains take a 90 deg downward turn at the end of their run.  On the longer problem loop the return drops all the way to floor level at the point it reaches back to the boiler.

    The shorter "working" main ends takes a 90 deg downward turn to about 6" below the main itself and returns to the setup behind the boiler at approx 6' above the ground.  I hope my sketch helps.
  • Boiler Info


  • Rod
    Rod Posts: 2,067
    Piping Diagram

    Hi- The diagram is a big help.

    Question:  Is the vent shown in your diagram the only main vent on the whole system?


    The "fix" on the piping looks pretty easy to do. With that and having the boiler piping reconfigured you should  then be in good shape.  The books will REALLY help you and also we will be better able to your questions by referring you to a certain page.

    On the boiler piping - Here is a good link to a video of Dan’s which explains why the configuration  of the boiler piping is so important.


       I'm out in California visiting so time and computer access is a bit short at the moment but I 'll will try to diagram out something for you tomorrow.

    - Rod
  • Vent


    That is the only vent that I can see.  it is about 5-6" in diameter and approx 8" tall.

    Happy Holidays
  • Mark N
    Mark N Member Posts: 1,094
    Main Vent

    Could that main vent possibly be a Mouat Bullet vent.  Looks very similar to the one on Gerry Gill's site
  • Rod
    Rod Posts: 2,067
    System Piping Modifications

    Hi - Using your drawing I drew out a modification of approximately how your system piping should be configured. (I've attached it as a PDFbelow)

    Based on the old vent and what looks like Mouat elbows attached to  your radiators’ return  port, as Mark mentioned, it looks like your system was probably originally a Mouat Vapor System. ( Page 256 & 257 in The Lost Art of Steam Heating).


    You might also want to take a look at Gerry Gill’s website. Gerry is a very experienced Cleveland steam pro and has some very good information on steam heating and on the Moust system.on his website  http://www.gwgillplumbingandheating.com/

    Do you have the Installation manual for your new boiler?  If not, let me know and I’ll send it to you.

    - Rod
  • gerry gill
    gerry gill Member Posts: 3,070
    I sent you a private email.

    I'll try to help you out via email.
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • gerry gill
    gerry gill Member Posts: 3,070

    you come up with some of the coolest pictures..where ever do you find them?
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Rod
    Rod Posts: 2,067
    Mouat System

    Hi- I see Gerry Gill has replied to your post. As I mentioned earlier, he is a very experienced steam pro and is an expert on Mouat Vapor systems so his advice is the one to follow if there is any conflict in the information you are receiving from either me or anyone else.

       On websites like this one, you usually get multiple answers to your questions from different sources. In some cases these answers many conflict with each other and that can result in confusion as you then don’t know which advice to follow so I thought I’d better clarify who is the expert here.

    A very Merry Christmas to you!

    - Rod
  • thankd

    Thanks all

    Still trying to figure this out.

    Merry Christmas
  • Orifices

    I am still trying to figure this out.  If the system did have orifices in the inlet or the outlet at one time and were removed, should I see any heating at all? Without taking a rad off is there any clear indication that the orifices were removed by system performance or lack there of?

    BRIANJ Member Posts: 118
    Look in the library

    If you go to the Resources Section at the top of the page and click on Library you can find a lot of original information on your Mouat system. Good Luck
  • Some Updates

    Happy New Year All

    Thanks For the ongoing help.  I have removed a radiator to check for some type of orifice at the inlet or outlet of the radiators.  There are none.  Is this what causes the inbalaces in my system?  All hand-valves and return els are the same on my two pipe system. 

    Another issue is the size of the boiler.  For fun I measured my rads and calculated the sq ft. of all the radiators in the house.  I have 11 rads totaling 546.25 sq ft.  (This info came straight from "the Lost Art...") So based on the figs in the book that would be 546.25 * 1.5 = 819.375 * 240 = 196650 MBH.  My boiler is a Utica SFE 3100 with a DOE max of 116000  and steam sq ft of 363. 


    1.  Now that I have some evidence that my rads do not have any orifices or traps, what is the best way to resolve this?

    2. Will I ever be able to do anything with the existing boiler? (it is only months old)

    3. I have gas service in my home.  If it is necessary to replace my boiler is there a realistic gas alternative?

    Thanks to all
  • Resoloution

    Thanks All,

    I ended up ordering inlet orifices sized to my radiators from Tunstall Inc.  They were great to deal with.  Installing the orifices was easy and they were inexpensive.  My home heats evenly and there is no water hammer.  It is impressive how a simple change resolved all of my issues. 

    I appreciate all the help.

    Should I consider switching to gas next time I need to replace the boiler?  Should I be considering any upgrades that would increase the efficiency of my system in the coming years?
  • Radiant?

    I am happy with the performance of my system now.

    When it is time to replace what would be the best option?  Someone had mentioned using radiant for the 1st floor and converting the second floor to hot water in the original radiators. (they are HW type check the pics.) If the original rads were not available install think European style rads.

    Does anyone have any ideas of the best replacement option for the future?  I am willing to entertain all options.

  • Pressure testing a steam system

    In order to see what might happen with a hot water conversion, plug off any vents, and pressurize your whole system to 30 psi, and then check for any leaks at any joint throughout the system, including the radiator sections. There are bound to be some as you are increasing the pressures by a factor of 30 times over the original design.

    In addition to that, then do a radiator survey, corrected for hot water temperatures for each room to see how much heat the rads can emit at 190 deg.

    Or you can just continue making the improvements to the present system, and still enjoy greater comfort, economy, and silence!--NBC
  • Dave in QCA
    Dave in QCA Member Posts: 1,777
    edited February 2012

    It sounds like you have completely resolved your steam system issues.  An orifice system is great!  You can't get better balance and distrubution, even on short steaming cycles in mild weather.

    There are so many issues with chaning over to hot water, and the savings that are usually claimed are not there.  I would take a while to get accustomed to your system and then see where there is issues that nead to be dealt with.

    Depending on where you live, firing gas can save a lot of money.  Of course, you might be able to convert the boiler you have by changing out the burner.

    I agree with you comments on Tunstall.  I also found them great to deal with!
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
This discussion has been closed.